New pyrrolidine-carboxamide derivatives as dual antiproliferative EGFR/CDK2 inhibitors

Cancer is one of the leading causes of mortality worldwide, making it a public health concern. A novel series of pyrrolidine-carboxamide derivatives 7a-q were developed and examined in a cell viability assay utilizing a human mammary gland epithelial cell line (MCF-10A), where all the compounds exhibited no cytotoxic effects and more than 85% cell viability at a concentration of 50 μM. Antiproliferative activity was evaluated in vitro against four panels of cancer cell lines A-549, MCF-7, Panc-1, and HT-29. Compounds 7e, 7g, 7k, 7n, and 7o were the most active as antiproliferative agents capable of triggering apoptosis. Compound 7g was the most potent of all the derivatives, with a mean IC50 of 0.90 μM compared to IC50 of 1.10 μM for doxorubicin. Compound 7g inhibited A-549 (epithelial cancer cell line), MCF-7 (breast cancer cell line), and HT-29 (colon cancer cell line) more efficiently than doxorubicin. EGFR inhibitory assay results of 7e, 7g, 7k, 7n, and 7o demonstrated that the tested compounds inhibited EGFR with IC50 values ranging from 87 to 107 nM in comparison with the reference drug erlotinib (IC50  = 80 nM). 7e, 7g, 7k, 7n, and 7o inhibited CDK2 efficiently in comparison to the reference dinaciclib (IC50  = 20 nM), with IC50 values ranging from 15 to 31 nM. The results of inhibitory activity assay against different CDK isoforms revealed that the tested compounds had preferential inhibitory activity against the CDK2 isoform.

Benzothiazole-Propanamide Linker Pyrrolidine (Morpholine) as Monoamine Oxidase-B and Butyrylcholinesterase Inhibitors

According to the fusion technique create effective multi-target-directed ligands, in this study, we designed and synthesized a series of benzo[d]thiazol-2-yl)-3-(pyrrolidin-1-yl) or 3-(morph- olino-1-yl)propanamide derivatives, and evaluated their inhibitory potency against MAOs, AChE, BuChE by in vitro enzyme effect assays. Based on activity results, we found that derivatives N-(5-methylbenzo[d]thiazol-2-yl)-3-(pyrrolidin-1-yl)propanamide (2 c) and N-(6-bromobenzo[d]thiazol-2-yl)-3-(pyrrolidin-1-yl)propanamide (2 h) showed good inhibitory potency against BuChE with IC50 values of 15.12 μM and 12.33 μM, respectively. Besides, 2 c and 2 h also exhibited selective MAO-B inhibitory effects with inhibition rates of 60.10 % and 66.30 % at 100 μM, respectively. In contrast, all designed derivatives were poor active against AChE and MAO-A at a concentration of 100 μM. The toxicity analysis in vitro by MTT and AO/EB fluorescence staining confirmed that 2 c and 2 h were nontoxic up to 100 μM. Molecular modeling studies showed that 2 c and 2 h could bind to the active site of BuChE. This research paves the way for further study aimed at designing MAO-B and BuChE inhibitors for the treatment of neurodegenerative disorders.

Crystal structures of five halido gold complexes involving piperidine or pyrrolidine as ligands or (protonated) as cations

In bromido-(pyrrolidine-κN)gold(I) bis-(pyrrolidine-κN)gold(I) bromide, [AuBr(pyr)]·[Au(pyr)2]Br (pyr = pyrrolidine, C4H9N), 2, alternating [AuBr(pyr)] mol-ecules and [Au(pyr)2]+ cations are connected by aurophilic contacts to form infinite chains of residues parallel to the b axis. The chains are cross-linked by three N-H⋯Br- hydrogen bonds and an Au⋯Br contact to form a layer structure parallel to the ab plane. Tri-chlorido-(piperidine-κN)gold(III), [AuCl3(pip)] (pip = piperidine, C5H11N), 3, consists of mol-ecules with the expected square-planar coordination at the gold atom, which are connected by an N-H⋯Cl hydrogen bond and an Au⋯Cl contact to form a layer structure parallel to the ac plane. The structures of bis-(piperidinium) tetra-chlorido-aurate(III) chloride, (pipH)2[AuCl4]Cl, 4, and bis-(pyrrolidinium) tetra-bromido-aurate(III) bromide, (pyrH)2[AuBr4]Br, 6, are closely related but not isotypic. Compound 6 crystallizes in space group Ibam; the Au and two Br atoms of the anion lie in the mirror plane x, y, 0, whereas the bromide ions occupy special positions 0, 0.5, 0 and 0, 0.5, 0.25, with site symmetry 2/m. The NH2 group forms a hydrogen bond to one bromide ion, and also a three-centre hydrogen bond to the other bromide atom and to a metal-bonded Br atom. The packing involves chains of hydrogen-bonded pyrrolidinium and bromide ions parallel to the c axis, combined with a layer structure of [AuBr4]- and bromide anions, parallel to the ab plane and involving Au⋯Br and Br⋯Br contacts. Compound 4, however, crystallizes pseudosymmetrically in space group Iba2; two chlorine atoms of the anion lie on the twofold axis 0.5, 0.5, z, and there are two independent cations. The packing is closely similar to that of 6, but there are no N-H⋯Cl hydrogen bonds to metal-bonded chlorines. The contact distances Au⋯Cl are appreciably longer than their Au⋯Br counterparts in 6, whereas the Cl⋯Cl contact is much shorter than Br⋯Br in 6. Tri-bromido-(piperidine-κN)gold(III) crystallizes as its di-chloro-methane solvate, [AuBr3(pip)]·CH2Cl2, 7. It too displays a square-planar coordination at the gold atom. The packing involves hydrogen bonds N-H⋯Br, stacking of neighbouring AuBr3 units by Au⋯Br contacts, and a short Br⋯Br contact; these combine to form a layer structure parallel to the ac plane.

Regioselective ring opening of aziridine for synthesizing azaheterocycle

Aziridine had different regioselective ring openings depending on the functional group of its alkyl substituent. In the case of the alkyl group bearing γ-ketone at the C2 substituent of aziridine, the ring opening by the hydroxy nucleophile from H2O occurred by attacking the aziridine carbon at the C2 position. This reaction proceeded efficiently in the presence of CF3CO2H. Interestingly, the same starting aziridine ring bearing the alkyl substituent at the C2 position with the γ-silylated hydroxy group instead of γ-ketone led to the ring-opening reaction by the same oxygen nucleophile at the unsubstituted C3 position, with the breakage of the bond between aziridine N1 nitrogen and carbon at C3. These reaction products were cyclized to afford substituted pyrrolidine and piperidine rings with representative examples of congeners of pseudoconhydrine and monomorine.

Recent insights about pyrrolidine core skeletons in pharmacology

To overcome numerous health disorders, heterocyclic structures of synthetic or natural origin are utilized, and notably, the emergence of various side effects of existing drugs used for treatment or the resistance of disease-causing microorganisms renders drugs ineffective. Therefore, the discovery of potential therapeutic agents that utilize different modes of action is of utmost significance to circumvent these constraints. Pyrrolidines, pyrrolidine-alkaloids, and pyrrolidine-based hybrid molecules are present in many natural products and pharmacologically important agents. Their key roles in pharmacotherapy make them a versatile scaffold for designing and developing novel biologically active compounds and drug candidates. This review aims to provide an overview of recent advancements (especially during 2015-2023) in the exploration of pyrrolidine derivatives, emphasizing their significance as fundamental components of the skeletal structure. In contrast to previous reviews that have predominantly focused on a singular biological activity associated with these molecules, this review consolidates findings from various investigations encompassing a wide range of important activities (antimicrobial, antiviral, anticancer, anti-inflammatory, anticonvulsant, cholinesterase inhibition, and carbonic anhydrase inhibition) exhibited by pyrrolidine derivatives. This study is also anticipated to serve as a valuable resource for drug research and development endeavors, offering significant insights and guidance.

1-(Pyrrolidin-1-yl)ethan-1-iminium chloride

The title compound, C6H13N2 +·Cl-, is as an amidinium salt that was isolated as unexpected product from the reaction between aceto-nitrile, chloro-form and pyrrolidine under refluxing conditions. The packing features two N-H⋯Cl hydrogen bonds to generate centrosymmetric tetra-mers (two cations and two anions) and van der Waals inter-actions.

Involvement of Both Extrinsic and Intrinsic Apoptotic Pathways in Tridecylpyrrolidine-Diol Derivative-Induced Apoptosis In Vitro

Despite the decreasing trend in mortality from colorectal cancer, this disease still remains the third most common cause of death from cancer. In the present study, we investigated the antiproliferative and pro-apoptotic effects of (2S,3S,4R)-2-tridecylpyrrolidine-3,4-diol hydrochloride on colon cancer cells (Caco-2 and HCT116). The antiproliferative effect and IC₅₀ values were determined by the MTT and BrdU assays. Flow cytometry, qRT-PCR and Western blot were used to study the cellular and molecular mechanisms involved in the induction of apoptotic pathways. Colon cancer cell migration was monitored by the scratch assay. Concentration-dependent cytotoxic and antiproliferative effects on both cell lines, with IC₅₀ values of 3.2 ± 0.1 μmol/L (MTT) vs. 6.46 ± 2.84 μmol/L (BrdU) for HCT116 and 2.17 ± 1.5 μmol/L (MTT) vs. 1.59 ± 0.72 μmol/L (BrdU), for Caco-2 were observed. The results showed that tridecylpyrrolidine-induced apoptosis was associated with the externalization of phosphatidylserine, reduced mitochondrial membrane potential (MMP) accompanied by the activation of casp-3/7, the cleavage of PARP and casp-8, the overexpression of TNF-α and FasL and the dysregulation of Bcl-2 family proteins. Inhibition of the migration of treated cells across the wound area was detected. Taken together, our data show that the anticancer effects of tridecylpyrrolidine analogues in colon cancer cells are mediated by antiproliferative activity, the induction of both extrinsic and intrinsic apoptotic pathways and the inhibition of cell migration.

Asymmetric Syntheses of Enantioenriched 2,5-Disubstituted Pyrrolidines

C₂-Symmetrical scaffolds are privileged ligands in metal catalysis and are also widely used in organocatalysis. Among these, 2,5-disubstituted pyrrolidines hold a paramount importance, especially since they also find application in medicinal chemistry. This review highlights the stereoselective syntheses of these C₂-symmetrical nitrogen heterocycles. It includes synthetic strategies based on the use of the chiral pool as well as the more recent sequences designed following major achievements in asymmetric catalysis.

Solvolysis of 2'-deoxyribonucleosides and oligo-2'-deoxyribonucleotides in aqueous pyrrolidine or ammonia solutions

To assess the feasibility of high-temperature aminolysis of deoxyribooligonucleotides containing rare bases as a method to determine their base sequence, the 2'-β-D-deoxyribosides of 5-bromouracil, 2-aminopurine, uracil, adenine, cytosine, 5-methylcytosine, hypoxanthine, N6-methyladenine, N4-ethylcytosine, and guanine were compared as to their rate of degradation in 0.5 M aqueous pyrrolidine at 110 °C, conditions used earlier in the analysis of oligonucleotides containing only the canonical bases. The reaction mixtures were analyzed by chromatography on Zorbax XDB-CN and UV absorption spectroscopy. The first-order rate constants for the nucleoside degradations decreased in the above order, spanning a wide range of reactivities. Some of these nucleosides were also tested in 0.5 M aqueous ammonia at 110 °C, giving similar first-order rate constants, except for 2'-deoxyguanosine, which is much more reactive with ammonia, due to the lower basicity of this reagent, leaving a larger proportion of the nucleoside in the non-ionized form, susceptible to nucleophilic attack at the base. Short oligothymidylates containing a single 2-aminopurine, adenine, guanine, or cytosine unit in central position were tested in pyrrolidinolysis, to determine the cleavage rates at these sites and the dependence of these cleavage rates on oligonucleotide length. A model decadeoxyribonucleotide containing all four canonical bases was also pyrrolidinolyzed, followed by ion-exchange chromatography, to deduce the nucleotide sequence from the resulting chromatographic profile.

Structural, Electric and Dynamic Properties of (Pyrrolidinium)3[Bi2I9] and (Pyrrolidinium)3[Sb2I9]: New Lead-Free, Organic-Inorganic Hybrids with Narrow Band Gaps

Hybrid organic-inorganic iodides based on Bi(III) and Sb(III) provide integrated functionalities through the combination of high dielectric constants, semiconducting properties and ferroic phases. Here, we report a pyrrolidinium-based bismuth (1) and antimony (2) iodides of (NC₄H₁₀)₃[M₂I₉] (M: Bi(III), Sb(III)) formula which are ferroelastic at room temperature. The narrow band gaps (~2.12 eV for 1 and 2.19 eV for 2) and DOS calculations indicate the semiconducting characteristics of both materials. The crystal structure consists of discrete, face-sharing bioctahedra [M₂I₉]^3- and disordered pyrrolidinium amines providing charge balance and acting as spacers between inorganic moieties. At room temperature, 1 and 2 accommodate orthorhombic Cmcm symmetry. 1 displays a complex temperature-induced polymorphism. It is stable up to 525 K and undergoes a sequence of low-temperature phase transitions (PTs) at 221/222 K (I ↔ II) and 189/190 K (II ↔ III) and at 131 K (IV→III), associated with the ordering of pyrrolidinium cations and resulting in Cmcm symmetry breaking. 2 undergoes only one PT at T = 215 K. The dielectric studies disclose a relaxation process in the kilohertz frequency region, assigned to the dynamics of organic cations, described well by the Cole-Cole relation. A combination of single-crystal X-ray diffraction, synchrotron powder diffraction, spin-lattice relaxation time of ¹H NMR, dielectric and calorimetric studies is used to determine the structural phase diagram, cation dynamics and electric properties of (NC₄H₁₀)₃[M₂I₉]_.

Azomethine Ylides-Versatile Synthons for Pyrrolidinyl-Heterocyclic Compounds

Azomethine ylides are nitrogen-based three-atom components commonly used in [3+2]-cycloaddition reactions with various unsaturated 2π-electron components. These reactions are highly regio- and stereoselective and have attracted the attention of organic chemists with respect to the construction of diverse heterocycles potentially bearing four new contiguous stereogenic centers. This review article complies the most important [3+2]-cycloaddition reactions of azomethine ylides with various olefinic, unsaturated 2π-electron components (acyclic, alicyclic, heterocyclic, and exocyclic ones) reported over the past two decades.

1,4-Dideoxy-1,4-imino-D- and L-lyxitol-based inhibitors bind to Golgi α-mannosidase II in different protonation forms

The development of effective inhibitors of Golgi α-mannosidase II (GMII, E.C.3.2.1.114) with minimal off-target effects on phylogenetically-related lysosomal α-mannosidase (LMan, E.C.3.2.1.24) is a complex task due to the complicated structural and chemical properties of their active sites. The pKa values (and also protonation forms in some cases) of several ionizable amino acids, such as Asp, Glu, His or Arg of enzymes, can be changed upon the binding of the inhibitor. Moreover, GMII and LMan work under different pH conditions. The pKa calculations on large enzyme-inhibitor complexes and FMO-PIEDA energy decomposition analysis were performed on the structures of selected inhibitors obtained from docking and hybrid QM/MM calculations. Based on the calculations, the roles of the amino group incorporated in the ring of the imino-D-lyxitol inhibitors and some ionizable amino acids of Golgi-type (Asp270-Asp340-Asp341 of Drosophila melanogaster α-mannosidase dGMII) and lysosomal-type enzymes (His209-Asp267-Asp268 of Canavalia ensiformis α-mannosidase, JBMan) were explained in connection with the observed inhibitory properties. The pyrrolidine ring of the imino-D-lyxitols prefers at the active site of dGMII the neutral form while in JBMan the protonated form, whereas that of imino-L-lyxitols prefers the protonation form in both enzymes. The calculations indicate that the binding mechanism of inhibitors to the active-site of α-mannosidases is dependent on the inhibitor structure and could be used to design new selective inhibitors of GMII. A series of novel synthetic N-substituted imino-D-lyxitols were evaluated with four enzymes from the glycoside hydrolase GH38 family (two of Golgi-type, Drosophila melanogaster GMIIb and Caenorhabditis elegans AMAN-2, and two of lysosomal-type, Drosophila melanogaster LManII and Canavalia ensiformis JBMan, enzymes). The most potent structures [N-9-amidinononyl and N-2-(1-naphthyl)ethyl derivatives] inhibited GMIIb (Ki = 40 nM) and AMAN-2 (Ki = 150 nM) with a weak selectivity index (SI) toward Golgi-type enzymes of IC50(LManII)/IC50(GMIIb) = 35 or IC50(JBMan)/IC50(AMAN-2) = 86. On the other hand, weaker micromolar inhibitors, such as N-2-naphthylmethyl or 4-iodobenzyl derivatives [IC50(GMIIb) = 2.4 μM and IC50 (AMAN-2) = 7.6 μM], showed a significant SI in the range from 111 to 812.

Pyrrolidine derivatives as antibacterial agents, current status and future prospects: a patent review

Bacterial infections are increasingly epitomizing major global health concerns, with rising death rates. Since the most complete assessment of the worldwide impact of antimicrobial resistance to date, with over 1.2 million people dead in 2019 as a direct result of antibiotic-resistant bacterial infections. The majority of antimicrobial drugs have been associated with a multitude of adverse effects including financial costs as well. Pyrrolidine derivatives have sparked the interest of researchers to create novel synthetic molecules with minimal side effect and drawbacks. To close the research gap, the current review discusses the synthetic compounds with active pyrrolidine scaffolds, critical findings and most crucially the structure-activity relationship that affects the activity of the ring over the last one and half decade.

3,4-Unsubstituted 2-tert-Butyl-pyrrolidine-1-oxyls with Hydrophilic Functional Groups in the Side Chains

Pyrrolidine nitroxides with four bulky alkyl substituents adjacent to N–O group are known for their high resistance to bioreduction. The 3,4-unsubstituted 2-tert-butyl-2-ethylpyrrolidine-1-oxyls were prepared from the corresponding 2-tert-butyl-1-pyrroline-1-oxides via either the addition of ethinylmagnesium bromide with subsequent hydrogenation or via treatment with ethyllithium. The new nitroxides showed excellent stability to reduction with ascorbate with no evidence for additional large hyperfine couplings in the EPR spectra.

Synthesis of Pyrrolidine- and γ-Lactam-Containing Natural Products and Related Compounds from Pyrrole Scaffolds

Polycyclic alkaloid natural products featuring pyrrolidine and pyrrolidinone motifs remain enduring targets of total synthesis endeavors. Pyrrole and its derivatives have been exploited to access many such frameworks, including alkaloids belonging to the Aspidosperma, Stemona, and batzelladine families. In this article, a selection of exemplars that highlight the utility of pyrrole-based approaches to facilitate total syntheses of pyrrolidine- and pyrrolidinone-containing alkaloids and related molecules are showcased.

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

The synthesis of bifunctional N-sulfinylureas and thioureas with an appended pyrrolidine unit is presented. These organocatalysts were evaluated in Michael additions of aldehydes to nitroalkenes both under solvent-free conditions and in solution. The N-sulfinylurea catalyst was more efficient than the corresponding thiourea. For some substrates, enantioselectivities reached 98% ee. The stereogenic center on the sulfur did not have a considerable influence on the catalytic reactions. Under ball-milling conditions, the Michael adducts were obtained in good yields but with slightly lower enantiomeric purities than in solution. DFT calculations elucidated its mode of action and confirmed a dual activation mode, which combines enamine activation of aldehydes and hydrogen-bond activation of nitroalkenes.

Structural Modification, In Vitro, In Vivo, Ex Vivo, and In Silico Exploration of Pyrimidine and Pyrrolidine Cores for Targeting Enzymes Associated with Neuroinflammation and Cholinergic Deficit in Alzheimer's Disease

To obtain a multipotent framework that can target simultaneously COX-2, 5-LOX, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) to treat neuroinflammation, a series of derivatives containing pyrimidine and pyrrolidine cores were rationally synthesized and evaluated. Pyrazoline-pyrimidine hybrid (23g), (3-acetylcoumarin derivative of pyrrolidin-1-yl)benzenesulfonamide (27), and tacrine derivatives of (pyrrolidin-1-yl)benzenesulfonamide (31, 38) displayed excellent in vitro COX-2 inhibition having IC₅₀ value in the nanomolar range. Tacrine-pyrrolidine hybrids 36 and 38, and tacrine-pyrimidine hybrid (46) emerged as the most potent eeAChE inhibitors with IC₅₀ values of 23, 16, and 2 nM, respectively. However, compounds 27, 31, and 38 possessed excellent simultaneous and balanced inhibitory activity against all of the four tested targets and thus emerged as optimal multipotent hybrid compounds among all of the synthesized series of the compounds. In the ex vivo, transgenic animal models treated with compounds 36 and 46 displayed a significant decline in both AChE and BChE potentials in the hippocampus and cortical tissues. In anti-inflammatory activities, animals treated with compounds 36 and 46 displayed a significant % inhibition of edema induced by carrageenan and arachidonic acid. Biochemical analysis and histopathological examination of mice liver indicate that tacrine derivatives are devoid of hepatotoxicity and neurotoxicity against SH-SY5Y neuroblastoma cell lines. In vivo acute toxicity study showed the safety of synthesized compounds up to 1000 mg/kg dose. The inhibitory manner of interaction of these potent drugs on all of the studied in vitro targets was confirmed by molecular docking investigations.

Asymmetric Synthesis of Enantiopure Pyrrolidines by C(sp3 )-H Amination of Hydrocarbons

The asymmetric synthesis of enantiopure pyrrolidines is reported via a streamlined strategy relying on two sequential C-H functionalizations of simple hydrocarbons. The first step is a regio- and stereoselective catalytic nitrene C-H insertion. Then, a subsequent diastereoselective cyclization involving a 1,5-hydrogen atom transfer (HAT) from a N-centered radical leads to the formation of pyrrolidines that can then be converted to their free NH-derivatives.

A Simple Method of Synthesis of 3-Carboxy-2,2,5,5-Tetraethylpyrrolidine-1-oxyl and Preparation of Reduction-Resistant Spin Labels and Probes of Pyrrolidine Series

Stable free radicals are widely used as molecular probes and labels in various biophysical and biomedical research applications of magnetic resonance spectroscopy and imaging. Among these radicals, sterically shielded nitroxides of pyrrolidine series demonstrate the highest stability in biological systems. Here, we suggest new convenient procedure for preparation of 3-carboxy-2,2,5,5-tetraethylpyrrolidine-1-oxyl, a reduction-resistant analog of widely used carboxy-Proxyl, from cheap commercially available reagents with the yield exceeding the most optimistic literature data. Several new spin labels and probes of 2,2,5,5-tetraethylpyrrolidine-1-oxyl series were prepared and reduction of these radicals in ascorbate solutions, mice blood and tissue homogenates was studied.

Preparation of Antiproliferative Terpene-Alkaloid Hybrids by Free Radical-Mediated Modification of ent-Kauranic Derivatives

A convenient strategy for molecular editing of available ent-kauranic natural scaffolds has been developed based on radical mediated C-C bond formation. Iodine atom transfer radical addition (ATRA) followed by rapid ionic elimination and radical azidoalkylation were investigated. Both reactions involve radical addition to the exo-methylenic double bond of the parent substrate. Easy transformations of the obtained adducts lead to extended diterpenes of broad structural diversity and artificial diterpene-alkaloid hybrids possessing lactam and pyrrolidine pharmacophores. The cytotoxicity of selected diterpenic derivatives was examined by in vitro testing on several tumor cell lines. The terpene-alkaloid hybrids containing N-heterocycles with unprecedented spiro-junction have shown relevant cytotoxicity and promising selectivity indexes. These results represent a solid basis for following research on the synthesis of such derivatives based on available natural product templates.

Synthesis, Cytotoxic and Heparanase Inhibition Studies of 5-oxo-1-arylpyrrolidine-3- carboxamides of Hydrazides and 4-amino-5-aryl-4H-1,2,4-triazole-3-thiol

Design of chemically novel, biologically potent small heterocyclic molecules with anticancer activities, which targets the enzyme heparanase has gained prominent clinical interest. We have synthesized a novel class of carboxamide derivatives by coupling various substituted aromatic acid hydrazides and triazoleamine with pyrrolidine carboxylic acid by using coupling agents. The synthesized compounds are characterized by spectroscopic techniques such as FT-IR, HRMS and NMR. These compounds are investigated for cytotoxicity on different cancer cell lines and heparanase inhibitory activity. Most of them showed moderate heparanase inhibitory activity and good cytotoxicity.

Alkaloids of the Genus Datura: Review of a Rich Resource for Natural Product Discovery

The genus Datura (Solanaceae) contains nine species of medicinal plants that have held both curative utility and cultural significance throughout history. This genus’ particular bioactivity results from the enormous diversity of alkaloids it contains, making it a valuable study organism for many disciplines. Although Datura contains mostly tropane alkaloids (such as hyoscyamine and scopolamine), indole, beta-carboline, and pyrrolidine alkaloids have also been identified. The tools available to explore specialized metabolism in plants have undergone remarkable advances over the past couple of decades and provide renewed opportunities for discoveries of new compounds and the genetic basis for their biosynthesis. This review provides a comprehensive overview of studies on the alkaloids of Datura that focuses on three questions: How do we find and identify alkaloids? Where do alkaloids come from? What factors affect their presence and abundance? We also address pitfalls and relevant questions applicable to natural products and metabolomics researchers. With both careful perspectives and new advances in instrumentation, the pace of alkaloid discovery—from not just Datura—has the potential to accelerate dramatically in the near future.

Microwave-Assisted Synthesis, Structural Characterization and Assessment of the Antibacterial Activity of Some New Aminopyridine, Pyrrolidine, Piperidine and Morpholine Acetamides

A series of new acetamide derivatives 22–28 of primary and secondary amines and para-toluene sulphinate sodium salt have been synthesized under microwave irradiation and assessed in vitro for their antibacterial activity against one Gram-positive and two Gram-negative bacterial species such as S. pyogenes, E. coli, and P. mirabilis using the Mueller-Hinton Agar diffusion (well diffusion) method. The synthesized compounds with significant differences in inhibition diameters and MICs were compared with those of amoxicillin, ampicillin, cephalothin, azithromycin and doxycycline. All of the evaluated acetamide derivatives were used with varying inhibition concentrations of 6.25, 12.5, 37.5, 62.5, 87.5, 112.5 and 125 µg/mL. The results show that the most important antibacterial properties were displayed by the synthetic compounds 22 and 24, both of bear a para-chlorophenyl moiety incorporated into the 2-position moiety of acetamide 1. The molecular structures of the new compounds were determined using the FT-IR and ¹H-NMR techniques.

Crystal structure of (1'S,2'S,3S)-1'-benzoyl-2'-(4-meth-oxy-phen-yl)-1-methyl-2',5',6',10b'-tetra-hydro-1'H-spiro-[indoline-3,3'-pyrrolo-[2,1-a]isoquinolin]-2-one

The synthesis and crystal structure of the spiro title compound is presented.

In the title spiro compound, C₃₄H₃₀N₂O₃, the central pyrrolidine ring is fused with the tetra­hydro­iso­quinoline ring, both having distorted envelope conformations, with the flap atoms being C and N, respectively. The meth­oxy­phenyl group is attached to the pyrrolidine ring, and is disordered over two positions, with refined occupancies of 0.638 (6):0.362 (6) Å. The central pyrrolidine ring is inclined relative to the tetra­hydro­iso­quinoline group, such that the dihedral between the non-flap atoms of each ring system is 11.29 (7)°. The spiro-linkage creates a dihedral angle of 83.26 (5)° between the indolinone ring and the non-flap atoms of the pyrrolidine ring. In the crystal, mol­ecules are linked via C—H⋯O hydrogen bonds. For the major disorder component, these form C(11) chains that propagate parallel to the a axis.

2-Chloro-4-nitrobenzoic acid as a coformer with pharmaceutical cocrystals and molecular salts

A series of five binary complexes, i.e. three cocrystals and two molecular salts, using 2-chloro-4-nitrobenzoic acid as a coformer have been produced with five commonly available compounds, some of pharmaceutical relevance, namely, 2-chloro-4-nitrobenzoic acid-isonicotinamide (1/1), C₇H₄ClNO₄·C₆H₆N₂O, 2-chloro-4-nitrobenzoic acid-3,3-diethylpyridine-2,4(1H,3H)-dione (2/1), 2C₇H₄ClNO₄·C₉H₁₃NO₂, 2-chloro-4-nitrobenzoic acid-pyrrolidin-2-one (1/1), C₇H₄ClNO₄·C₄H₇NO, 2-carboxypiperidinium 2-chloro-4-nitrobenzoate, C₆H₁₂NO₂^-·C₇H₃ClNO₄^-, and (2-hydroxyethyl)ammonium 2-chloro-4-nitrobenzoate, C₂H₈NO⁺·C₇H₃ClNO₄^-. The coformer falls under the classification of a `generally regarded as safe' compound. All five complexes make use of a number of different heteromeric hydrogen-bonded interactions. Intermolecular potentials were evaluated using the CSD-Materials module.

4-Nitro-benzyl 3,4-bis-(acet-yloxy)-2-(4-meth-oxy-phen-yl)pyrrolidine-1-carboxyl-ate: crystal structure, Hirshfeld surface analysis and computational chemistry

The title compound, C23H24N2O9, is a tetra-substituted pyrrolidine derivative with a twisted conformation, with the twist evident in the C-C bond bearing the adjacent acet-yloxy substituents. These are flanked on one side by a C-bound 4-meth-oxy-phen-yl group and on the other by a methyl-ene group. The almost sp 2-N atom [sum of angles = 357°] bears a 4-nitro-benzyl-oxycarbonyl substituent. In the crystal, ring-methyl-ene-C-H⋯O(acet-yloxy-carbon-yl) and methyl-ene-C-H⋯O(carbon-yl) inter-actions lead to supra-molecular layers lying parallel to (01); the layers stack without directional inter-actions between them. The analysis of the calculated Hirshfeld surfaces indicates the combined importance of H⋯H (42.3%), H⋯O/O⋯H (37.3%) and H⋯C/C⋯H (14.9%) surface contacts. Further, the inter-action energies, largely dominated by the dispersive term, point to the stabilizing influence of H⋯H and O⋯O contacts in the inter-layer region.

1-Ethyl 2-methyl 3,4-bis-(acet-yloxy)pyrrolidine-1,2-di-carboxyl-ate: crystal structure, Hirshfeld surface analysis and computational chemistry

The title compound, C13H19NO8, is based on a tetra-substituted pyrrolidine ring, which has a twisted conformation about the central C-C bond; the Cm-Ca-Ca-Cme torsion angle is 38.26 (15)° [m = methyl-carboxyl-ate, a = acet-yloxy and me = methyl-ene]. While the N-bound ethyl-carboxyl-ate group occupies an equatorial position, the remaining substituents occupy axial positions. In the crystal, supra-molecular double-layers are formed by weak methyl- and methyl-ene-C-H⋯O(carbon-yl) inter-actions involving all four carbonyl-O atoms. The two-dimensional arrays stack along the c axis without directional inter-actions between them. The Hirshfeld surface is dominated by H⋯H (55.7%) and H⋯C/C⋯H (37.0%) contacts; H⋯H contacts are noted in the inter-double-layer region. The inter-action energy calculations point to the importance of the dispersion energy term in the stabilization of the crystal.

pKa Modulation of Pyrrolidine-Based Catalytic Polymers Used for the Preparation of Glycosyl Hydrazides at Physiological pH and Temperature

Inspired by the ability of enzymes to use the surrounding hydrophobic and/or polarizable groups to modulate the pK_a of a given amino acid, we designed a series of soluble polymers able to decrease the basicity of pyrrolidine (from 11.2 to 8.6 pK_a units), which clearly increases its aminocatalytic activity at physiological pH in C═N bond formation reactions via ion iminium activation. Other parameters such as charge density, hydrophobic/hydrophilic balance, and aggregation state have been studied as important factors in the catalytic activity of the polymers for a given substrate. To demonstrate the utility of our approach, an optimal pyrrolidine-based catalytic polymer has been used for the formation of C-N bonds between hydrazides and free sugars as the model system for the preparation of glycoconjugates.

Beyond the Simple Copper(II) Coordination Chemistry with Quinaldinate and Secondary Amines

Copper(II) acetate has reacted in methanol with quinaldinic acid (quinoline-2-carboxylic acid) to form [Cu(quin)₂(CH₃OH)]∙CH₃OH (1) (quin⁻ = an anionic form of the acid) with quinaldinates bound in a bidentate chelating manner. In the air, complex 1 gives off methanol and binds water. The conversion was monitored by IR spectroscopy. The aqua complex has shown a facile substitution chemistry with alicyclic secondary amines, pyrrolidine (pyro), and morpholine (morph). trans-[Cu(quin)₂(pyro)₂] (2) and trans-[Cu(quin)₂(morph)₂] (4) were obtained in good yields. The morpholine system has produced a by-product, trans-[Cu(en)₂(H₂O)₂](morphCOO)₂ (5) (morphCOO⁻ = morphylcarbamate), a result of the copper(II) quinaldinate reaction with ethylenediamine (en), an inherent impurity in morpholine, and the amine reaction with carbon dioxide. (pyroH)[Cu(quin)₂Cl] (3) forms on the recrystallization of [Cu(quin)₂(pyro)₂] from dichloromethane, confirming a reaction between amine and the solvent. Similarly, a homologous amine, piperidine (pipe), and dichloromethane produced (pipeH)[Cu(quin)₂Cl] (11). The piperidine system has afforded both mono- and bis-amine complexes, [Cu(quin)₂(pipe)] (6) and trans-[Cu(quin)₂(pipe)₂] (7). The latter also exists in solvated forms, [Cu(quin)₂(pipe)₂]∙CH₃CN (8) and [Cu(quin)₂(pipe)₂]∙CH₃CH₂CN (9). Interestingly, only the piperidine system has experienced a reduction of copper(II). The involvement of amine in the reduction was undoubtedly confirmed by identification of a polycyclic piperidine compound 10, 6,13-di(piperidin-1-yl)dodecahydro-2H,6H-7,14-methanodipyrido[1,2-a:1′,2′-e][1,5]diazocine.

Synthesis of thiazolidin-4-ones and thiazinan-4-ones from 1-(2-aminoethyl)pyrrolidine as acetylcholinesterase inhibitors

The present study describes the synthesis of a novel series of thiazolidin-4-one and thiazinan-4-one using 1-(2-aminoethyl)pyrrolidine as amine precursor. All compounds were synthesised by one-pot three component cyclocondensation reaction from the amine, a substituted benzaldehyde and a mercaptocarboxylic acid. The compounds were obtained in moderate to good yields and were identified and characterised by ¹H, ¹³C, 2 D NMR and GC/MS techniques. The compounds also were screened for their in vitro acetylcholinesterase (AChE) activity in hippocampus and cerebral cortex on Wistar rats. The six most potent compounds have been investigated for their cytotoxicity by cell viability assay of astrocyte primary culture, an important cell of central nervous system. We highlighted two compounds (6a and 6k) that had the lowest IC₅₀ in hippocampus (5.20 and 4.46 µM) and cerebral cortex (7.40 and 6.83 µM). These preliminary and important results could be considered a starting point for the development of new AChE inhibitory agents.

The crystal structures and Hirshfeld surface analysis of 6-(naphthalen-1-yl)-6a-nitro-6,6a,6b,7,9,11a-hexa-hydro-spiro-[chromeno[3',4':3,4]pyrrolo-[1,2-c]thia-zole-11,11'-indeno-[1,2-b]quinoxaline] and 6'-(naphthalen-1-yl)-6a'-nitro-6',6a',6b',7',8',9',10',12a'-octa-hydro-2H-spiro-[ace-naphthyl-ene-1,12'-chromeno[3,4-a]indolizin]-2-one

The crystal structures of the title spiro derivatives are described and the analysis of the inter­molecular contacts in the crystals using Hirshfeld surface analysis and two-dimensional fingerprint plots is reported.

The title compounds, 6-(naphthalen-1-yl)-6a-nitro-6,6a,6 b,7,9,11a-hexa­hydro­spiro­[chromeno[3′,4′:3,4]pyrrolo­[1,2-c]thia­zole-11,11′-indeno­[1,2-b]quinoxaline], C₃₇H₂₆N₄O₃S, (I), and 6′-(naphthalen-1-yl)-6a′-nitro-6′,6a′,6b′,7′,8′,9′,10′,12a′-octa­hydro-2H-spiro­[ace­naphthyl­ene-1,12′-chromeno[3,4-a]indolizin]-2-one, C₃₆H₂₈N₂O₄, (II), are new spiro derivatives, in which both the pyrrolidine rings adopt twisted conformations. In (I), the five-membered thia­zole ring adopts an envelope conformation, while the eight-membered pyrrolidine-thia­zole ring adopts a boat conformation. An intra­molecular C—H⋯N hydrogen bond occurs, involving a C atom of the pyran ring and an N atom of the pyrazine ring. In (II), the six-membered piperidine ring adopts a chair conformation. An intra­molecular C—H⋯O hydrogen bond occurs, involving a C atom of the pyrrolidine ring and the keto O atom. For both compounds, the crystal structure is stabilized by inter­molecular C—H⋯O hydrogen bonds. In (I), the C—H⋯O hydrogen bonds link adjacent mol­ecules, forming R₂²(16) loops propagating along the b-axis direction, while in (II) they form zigzag chains along the b-axis direction. In both compounds, C—H⋯π inter­actions help to consolidate the structure, but no significant π–π inter­actions with centroid–centroid distances of less than 4 Å are observed.

Synthesis of Novel 2-(Het)arylpyrrolidine Derivatives and Evaluation of Their Anticancer and Anti-Biofilm Activity

A library of novel 2-(het)arylpyrrolidine-1-carboxamides were obtained via a modular approach based on the intramolecular cyclization/Mannich-type reaction of N-(4,4-diethoxybutyl)ureas. Their anti-cancer activities both in vitro and in vivo were tested. The in vitro activity of some compounds towards M-Hela tumor cell lines was twice that of the reference drug tamoxifen, whereas cytotoxicity towards normal Chang liver cell did not exceed the tamoxifen toxicity. In vivo studies showed that the number of surviving animals on day 60 of observation was up to 83% and increased life span (ILS) was up to 447%. Additionally, some pyrrolidine-1-carboxamides possessing a benzofuroxan moiety obtained were found to effectively suppress bacterial biofilm growth. Thus, these compounds are promising candidates for further development both as anti-cancer and anti-bacterial agents.

Synthesis of pyrrolo[1,2-a]quinolines by formal 1,3-dipolar cycloaddition reactions of quinolinium salts

Quinolinium salts, Q⁺-CH₂-CO₂Me Br⁻ and Q⁺-CH₂-CONMe₂ Br⁻ (where Q = quinoline), were prepared from quinolines. Deprotonation of these salts with triethylamine promoted the reaction of the resulting quinolinium ylides (formally azomethine ylides) with electron-poor alkenes by conjugate addition followed by cyclization or by [3 + 2] dipolar cycloaddition. The pyrroloquinoline products were formed as single regio- and stereoisomers. These could be converted to other derivatives by Suzuki–Miyaura coupling, reduction or oxidation reactions.

Exploring isoxazoles and pyrrolidinones decorated with the 4,6-dimethoxy-1,3,5-triazine unit as human farnesyltransferase inhibitors

Unprecedented triazinyl-isoxazoles were afforded via an effective cycloaddition reaction between nitrile oxides and the scarcely described 2-ethynyl-4,6-dimethoxy-1,3,5-triazine as dipolarophile. The biological evaluation of the newly synthesized compounds showed that the inhibition of human farnesyltransferase by zinc complexation could be improved with triazine-isoxazole moieties. The replacement of the isoxazole unit by a pyrrolidin-2-one was detrimental to the inhibitory activity while the pyrrolidin-2-thione derivatives conserved the biological potential. The potential of selected compounds to disrupt protein farnesylation in Chinese hamster ovary (CHO) cells transfected with pEGFP-CAAX was also evaluated.

High-temperature solvolysis of 2'-deoxyribonucleosides in aqueous amine solutions

Degradation of 2'-deoxyribonucleosides in 0.5 M aqueous pyrrolidine at 110 °C proceeds at different rates, ordered as deoxyuridine > deoxyadenosine > deoxycytidine > deoxyguanosine ≫ deoxythymidine. Deoxyadenosine degradation produces the free base, adenine, while deoxycytidine by deamination produces deoxyuridine, and then uracil. The solvolysis of deoxyadenosine has an activation energy of 23.3 kcal/mol. Ammonolysis is slower than pyrrolidinolysis for deoxyadenosine, but faster for deoxyguanosine. In pyrrolidinolysis of the trinucleotides, d-TGT and d-TAT, the guanine moiety reacts faster than the adenine moiety. These trends are interpreted in terms of the ionization of the guanine moieties under basic conditions, rendering them less susceptible to nucleophilic attack.

Crystal structure of 6-(4-chloro-phen-yl)-6a-nitro-6a,6b,8,9,10,12a-hexa-hydro-6H,7H-spiro[chromeno[3,4-a]indolizine-12,11'-indeno-[1,2-b]quinoxaline]

The title compound, C35H27ClN4O3, crystallized with two independent mol-ecules (A and B) in the asymmetric unit. In both mol-ecules, the pyran and pyridine rings adopt envelope and chair conformations, respectively. The conformation of the pyrrolidine and cyclo-pentene rings differ in the two mol-ecules; twisted and flat, respectively, in mol-ecule A, but envelope and twisted, respectively, in mol-ecule B. In both mol-ecules, there is a C-H⋯N intra-molecular hydrogen bond present. In both mol-ecules, the oxygen atoms of the nitro groups are disordered as is the chlorine atom in mol-ecule B. In the crystal, the B mol-ecules are linked by C-H⋯O hydrogen bonds, forming -B-B-B- chains along [010], and by C-H⋯π inter-actions. The A and B mol-ecules are also linked by a number of C-H⋯π inter-actions, resulting in the formation a supra-molecular three-dimensional structure. In mol-ecule A, the nitro group oxygen atoms are disordered over two positions with refined occupancy ratios of the nitro group oxygen atoms O3A and O4A in 0.59 (2):0.41 (2) while in molecule B one of the nitro O atoms is disordered over two positions with a refined occupancy ratio of 0.686 (13):0.314 (13) and the chlorine atoms is disordered over two positions with a refined occupancy ratio of 0.72 (3):0.28 (3).

The crystal structures of 6'-(4-chloro-phen-yl)- and 6'-(4-meth-oxy-phen-yl)-6a'-nitro-6a',6b',7',9',10',12a'-hexa-hydro-2H,6'H,8'H-spiro-[ace-naphthyl-ene-1,12'-chromeno[3,4-a]indolizin]-2-one

The conformations of the title compounds, (I) and (II), are very similar. The pyran rings adopt envelope conformations, the piperidine rings have chair conformations and the pyrrolidine rings adopt twist conformations. Intra- and inter­molecular C—H⋯O hydrogen bonds occur. Compound (II) crystallizes with two independent mol­ecules in the asymmetric unit which are linked by C—H⋯O hydrogen bonds.

In the title compounds, C₃₂H₂₅ClN₂O₄ (I) and C₃₃H₂₈N₂O₅ (II), the six-membered pyran and piperidine rings adopt envelope and chair conformations, respectively. The five-membered pyrrolidine rings adopt twist conformations. Compound (II) crystallizes with two independent mol­ecules (A and B) in the asymmetric unit. In all three mol­ecules there is a C—H⋯O intra­molecular hydrogen bond present enclosing an S(7) ring motif. In (I), both oxygen atoms of the nitro group are disordered, while in (II) the meth­oxy­benzene group is disordered in mol­ecule B. The geometries were regularized by soft restraints. In the crystal of (I), mol­ecules are linked by C—H⋯O hydrogen bonds, forming chains along [010]. The chains are linked by C—H⋯Cl hydrogen bonds, forming layers parallel to (10). Within the layer there are C—H⋯π inter­actions present. In the crystal of (II), the A and B mol­ecules are linked via C—H⋯O hydrogen bonds, forming a square four-membered A–B–A–B unit. These units are linked by a number of C—H⋯π inter­actions, forming a three-dimensional supra­molecular structure.

Synthesis of pyrrolidine-based hamamelitannin analogues as quorum sensing inhibitors in Staphylococcus aureus

Interfering with bacterial cell-to-cell communication is a promising strategy to combat antimicrobial resistance. The natural product hamamelitannin and several of its analogues have been identified as quorum sensing inhibitors. In this paper the synthesis of pyrrolidine-based analogues of a more lead-like hamamelitannin analogue is reported. A convergent synthetic route based on a key ring-closing metathesis reaction was developed and delivered the pyrrolidine analogue in 17 steps in high yield. Chemoselective derivatization of the pyrrolidine nitrogen atom resulted in 6 more compounds. The synthesized compounds were evaluated in a biofilm model, but were all inactive.

One pot multi-component synthesis of functionalized spiropyridine and pyrido[2,3-d]pyrimidine scaffolds and their potent in-vitro anti-inflammatory and anti-oxidant investigations

A new series of functionalized fused pyridines 4(a-i) and fused pyrido[2,3-d]pyrimidines 8(a-c) were designed and synthesized through a multi-component reaction where in pyridine ring formation step plays a key role. All the newly formed compounds were well characterized by spectral techniques such as FTIR, ¹ HNMR, ¹³ CNMR, HRMS and XRD. The potential therapeutic activities such as anti-inflammatory activity by protein denaturation and RBC membrane stabilization methods, and anti-oxidant activity by DPPH scavenging method of the newly synthesized compounds were studied. Interestingly, in-vitro testing of these compounds reveals that the compounds 4d, 4g, 4i, 8a and 8b showed comparable anti-inflammatory activity with respect to the standard drug, diclofenac. Similarly, fused pyridine 4f showed excellent anti-oxidant activity when compared with the standard, ascorbic acid.

Synthesis and biological evaluation of pyrrolidine-based T-type calcium channel inhibitors for the treatment of neuropathic pain

The treatment of neuropathic pain is one of the urgent unmet medical needs and T-type calcium channels are promising therapeutic targets for neuropathic pain. Several potent T-type channel inhibitors showed promising in vivo efficacy in neuropathic pain animal models and are being investigated in clinical trials. Herein we report development of novel pyrrolidine-based T-type calcium channel inhibitors by pharmacophore mapping and structural hybridisation followed by evaluation of their Ca_v3.1 and Ca_v3.2 channel inhibitory activities. Among potent inhibitors against both Ca_v3.1 and Ca_v3.2 channels, a promising compound 20n based on in vitro ADME properties displayed satisfactory plasma and brain exposure in rats according to in vivo pharmacokinetic studies. We further demonstrated that 20n effectively improved the symptoms of neuropathic pain in both SNL and STZ neuropathic pain animal models, suggesting modulation of T-type calcium channels can be a promising therapeutic strategy for the treatment of neuropathic pain.

Palladium and Platinum 2,4-cis-amino Azetidine and Related Complexes

Seven N,N'-palladium(II) chloride complexes, one N,N'-palladium(II) acetate complex of 2,4-cis-azetidines where prepared and analyzed by single crystal XRD. Two platinum(II) chloride N,N'-complexes of 2,4-cis-azetidines where prepared and analyzed by single crystal XRD. Computational analysis and determination of the %Vbur was examined conducted. A CNN' metallocyclic complex was prepared by oxidative addition of palladium(0) to an ortho bromo 2,4-cis-disubstituted azetidine and its crystal structure displays a slightly pyramidalized metal-ligand orientation.

Discovery of Methyl (5 Z)-[2-(2,4,5-Trioxopyrrolidin-3-ylidene)-4-oxo-1,3-thiazolidin-5-ylidene]acetates as Antifungal Agents against Potato Diseases

Synthesis, isomerism, and fungicidal activity against potato diseases of new (5 Z)-[2-(2,4,5-trioxopyrrolidin-3-ylidene)-4-oxo-1,3-thiazolidin-5-ylidene]acetate derivatives with 1,3-thiazolidine-4-one and pyrrolidine-2,3,5-trione moieties linked by an exocyclic C═C bond were described. Their structures were clearly confirmed by spectroscopic and spectrometric data (Fourier transform infrared spectroscopy, ¹H and ¹³C nuclear magnetic resonance, and mass spectrometry), elemental analysis, and X-ray diffraction crystallography. A bioassay for antifungal activity in vitro against Phytophthora infestans, Fusariun solani, Alternaria solani, Rhizoctonia solani, and Colletotrichum coccodes demonstrated that 2,4,5-trioxopyrrolidin-1,3-thiazolidine derivatives exhibited a relatively broad spectrum of antifungal activity. One of the compounds showed considerable activity against all of the strains; in the case of F. solani, P. infestans, and A. solani, it possesses comparable or better fungicidal efficacy than the positive control Consento. Consequently, this compound is a promising fungicidal candidate for plant protection.

Cobalt-Catalyzed (Hetero)arylation of Saturated Cyclic Amines with Grignard Reagents

(Hetero)aryl substituted saturated cyclic amines are ubiquitous scaffolds in biologically active molecules. Metal-catalyzed cross-couplings between halogeno N-heterocycles and organometallic species are efficient and modular reactions to access these attractive scaffolds. An overview of our work concerning the cobalt-catalyzed arylation of iodo-substituted cyclic amines is presented.

Synthesis of Chlorotrifluoromethylated Pyrrolidines by Electrocatalytic Radical Ene-Yne Cyclization

The stereoselective synthesis of chlorotrifluoromethylated pyrrolidines was achieved using anodically coupled electrolysis, an electrochemical process that combines two parallel oxidative events in a convergent and productive manner. The bench-stable and commercially available solids CF₃ SO₂ Na and MgCl₂ were used as the functional group sources to generate CF₃^. and Cl^. , respectively, via electrochemical oxidation, and the subsequent reaction of these radicals with the 1,6-enyne substrate was controlled with an earth-abundant Mn catalyst. In particular, the introduction of a chelating ligand allowed for the ene-yne cyclization to take place with high stereochemical control over the geometry of the alkene group in the pyrrolidine product.

Crystal structure and Hirshfeld surface analysis of 4'-(2-chloro-phen-yl)-1'-methyl-3''-phenyl-7'',8''-di-hydro-5''H-di-spiro-[indoline-3,2'-pyrrolidine-3',6''-iso-quinoline]-2,5''-dione

In the title di-spiro compound, C₃₂H₂₆ClN₃O₂, the cyclo-hexa-none ring of the iso-quinoline unit has a distorted envelope conformation, with the methyl-ene C atom adjacent to the spiro C atom as the flap. The central 1-methyl-pyrrolidine ring has an envelope conformation with the N atom as the flap. The mean planes of the indolin-2-one ring system, the chloro-benzene ring and the iso-quinoline ring system are inclined to the mean plane of the central 1-methyl-pyrrolidine ring by 87.95 (11), 71.01 (12) and 88.81 (10)°, respectively. There are two short C-H⋯O intra-molecular contacts present. In the crystal, mol-ecules are linked via C-H⋯ O hydrogen bonds, forming chains along the a-axis direction. The NH H atom is involved in a weak N-H⋯O hydrogen bond with the same carbonyl O atom. There are no further significant inter-molecular contacts present. The largest contribution to the overall Hirshfeld surface of 52.3% is due to H-H contacts.

Crystal structure of (-)-(5R,7R,8S,9R,10S)-8-methyl-7-[(5R)-3-methyl-2-oxooxolan-3-en-5-yl]-1-aza-6-oxatri-cyclo-[8.3.0.05,9]tridecan-13-one monohydrate

The title compound, C17H23NO4·H2O, is an epimer of the natural tetra-cyclic alkaloid isosaxorumamide which consists of a fused 5-7-5 tricyclic core and a di-hydro-furan-one substituent. The terminal di-hydro-furan ring is essentially planar with a maximum deviation of 0.0273 (14) Å from the mean plane and oxolane, azepane and pyrrolidine rings in the tricyclic ring system adopt twist, twist-chair and envelope forms, respectively. In the crystal, the amide and water mol-ecules are linked by O-H⋯O hydrogen bonds, forming a tape structure running along the b-axis direction. The tapes are further connected by C-H⋯O inter-actions into a three-dimensional architecture.

Diastereoselective C-H Bond Amination for Disubstituted Pyrrolidines

We report herein the improved diastereoselective synthesis of 2,5-disubstituted pyrrolidines from aliphatic azides. Experimental and theoretical studies of the C-H amination reaction mediated by the iron dipyrrinato complex (Ad L)FeCl(OEt2 ) provided a model for diastereoinduction and allowed for systematic variation of the catalyst to enhance selectivity. Among the iron alkoxide and aryloxide catalysts evaluated, the iron phenoxide complex exhibited superior performance towards the generation of syn 2,5-disubstituted pyrrolidines with high diastereoselectivity.

A mechanochemical approach to access the proline-proline diketopiperazine framework

Ball milling was exploited to prepare a substituted proline building block by mechanochemical nucleophilic substitution. Subsequently, the mechanocoupling of hindered proline amino acid derivatives was developed to provide proline-proline dipeptides under solvent-free conditions. A deprotection-cyclization sequence yielded the corresponding diketopiperazines that were obtained with a high stereoselectivity which could be explained by DFT calculations. Using this method, an enantiopure disubstituted Pro-Pro diketopiperazine was synthesized in 4 steps, making 5 new bonds using a ball mill.

Crystal structure of 4-meth-oxy-N-(piperidine-1-carbono-thio-yl)benzamide

In the title compound, C14H18N2O2S, the piperidine ring has a chair conformation. Its mean plane is twisted with respect to the 4-meth-oxy-benzoyl ring, with a dihedral angle of 63.0 (3)°. The central N-C(=S)-N(H)-C(=O) bridge is twisted with an N-C-N-C torsion angle of 74.8 (6)°. In the crystal, mol-ecules are linked by N-H⋯O and C-H⋯O hydrogen bonds, forming chains along the c-axis direction. Adjacent chains are linked by C-H⋯π inter-actions, forming layers parallel to the ac plane. The layers are linked by offset π-π inter-actions [inter-centroid distance = 3.927 (3) Å], forming a supra-molecular three-dimensional structure.

Pyrrolidine-Containing Bisphosphonates as Potential Anti-Resorption Bone Drugs

Bisphosphonates, particularly those with N-substituted groups, are currently the most popular drugs for the treatment of osteoporosis. However, their chemical structures are still rather simple and new synthetic methods are needed to expand their molecular complexity and also improve their specificity of action towards other targets as anticancer, antibacterial, and antimalarial drugs. Herein, we report a new class of potential antiresorption bisphosphonate drugs that have a pyrrolidine unit with different substituents, obtained through a simple dipolar cycloaddition reaction between azomethine ylides and vinylidenebisphosphonate derivatives as precursors. The methodology led to the efficient preparation of a wide range of (1-methylpyrrolidine-3,3-diyl)bis(phosphonic esters) derivatives with different substituents in position 4.