Design and synthesis of 1,5- and 2,5-substituted tetrahydrobenzazepinones as novel potent and selective integrin alphaVbeta3 antagonists

Discovery and Characterization of RGH-122, a Potent, Selective, and Orally Bioavailable V1a Receptor Antagonist

The V1a receptor is a major contributor in mediating the social and emotional effects of arginine-vasopressin (AVP); therefore it represents a promising target in the treatment of several neuropsychiatric conditions. The aim of this research was to design and synthesize novel and selective V1a antagonists with improved in vitro and in vivo profiles. Through optimization and detailed SAR studies, we developed low nanomolar antagonists, and further characterizations led to the discovery of the clinical candidate compound 43 (RGH-122). The CNS activity of the compound was determined in a 3-chamber social preference test of autism in which RGH-122 successfully enhanced social preference with the lowest effective dose of 1.5 mg/kg.

N-substitution Reactions of 2-Aminobenzimidazoles to Access Pharmacophores

Benzimidazole (BI) and its derivatives are interesting molecules in medicinal chemistry because several of these compounds have a diversity of biological activities and some of them are even used in clinical applications. In view of the importance of these compounds, synthetic chemists are still interested in finding new procedures for the synthesis of these classes of compounds. Astemizole (antihistaminic), Omeprazole (antiulcerative), and Rabendazole (fungicide) are important examples of compounds used in medicinal chemistry containing BI nuclei. It is interesting to observe that several of these compounds contain 2-aminobenzimidazole (2ABI) as the base nucleus. The structures of 2ABI derivatives are interesting because they have a planar delocalized structure with a cyclic guanidine group, which have three nitrogen atoms with free lone pairs and labile hydrogen atoms. The 10-π electron system of the aromatic BI ring conjugated with the nitrogen lone pair of the hexocyclic amino group, making these heterocycles to have an amphoteric character. Synthetic chemists have used 2ABI as a building block to produce BI derivatives as medicinally important molecules. In view of the importance of the BIs, and because no review was found in the literature about this topic, we reviewed and summarized the procedures related to the recent methodologies used in the N-substitution reactions of 2ABIs by using aliphatic and aromatic halogenides, dihalogenides, acid chlorides, alkylsulfonic chlorides, carboxylic acids, esters, ethyl chloroformates, anhydrides, SMe-isothioureas, alcohols, alkyl cyanates, thiocyanates, carbon disulfide and aldehydes or ketones to form Schiff bases. The use of diazotized 2ABI as intermediate to obtain 2-diazoBIs was included to produce Nsubstituted 2ABIs of pharmacological interest. Some commentaries about their biological activity were included.

Synthesis of Bench-Stable N-Quaternized Ketene N,O-Acetals and Preliminary Evaluation as Reagents in Organic Synthesis

N-Quaternized ketene N,O-acetals are typically an unstable, transient class of compounds most commonly observed as reactive intermediates. In this report, we describe a general synthetic approach to a variety of bench-stable N-quaternized ketene N,O-acetals via treatment of pyridine or aniline bases with acetylenic ethers and an appropriate Brønsted or Lewis acid (triflic acid, triflimide, or scandium(III) triflate). The resulting pyridinium and anilinium salts can be used as reagents or synthetic intermediates in multiple reaction types. For example, N-(1-ethoxyvinyl)pyridinium or anilinium salts can thermally release highly reactive O-ethyl ketenium ions for use in acid catalyst-free electrophilic aromatic substitutions. N-(1-Ethoxyvinyl)-2-halopyridinium salts can be employed in peptide couplings as a derivative of Mukaiyama reagents or react with amines in nucleophilic aromatic substitutions under mild conditions. These preliminary reactions illustrate the broad potential of these currently understudied compounds in organic synthesis.

Fused-azepinones: Emerging scaffolds of medicinal importance

Hymenialdisine an alkaloid of oroidin class has drawn the attention of researchers owing to its unique structural features and interesting biological properties. Hymenialdisine exhibited promising inhibitory activity against a number of therapeutically important kinases viz., CDKs, GSK-3β etc., and showed anti-cancer, anti-inflammatory, anti-HIV, neuroprotective, anti-fouling, anti-plasmodium properties. Hymenialdisine and other structurally related oroidin alkaloids such as dibromo-hymenialdisine, stevensine, hymenin, axinohydantoin, spongicidines A-D, latonduines and callyspongisines contain pyrrolo[2,3-c] azepin-8-one core in common. Keeping in view of the interesting structural and therapeutic features of HMD, several structural modifications were carried around the fused-azepinone core which resulted in a number of diverse structural motifs like indolo-azepinones, paullones, aza-paullones, darpones and 5,7-dihydro-6H-benzo[b]pyrimido[4,5-d] azepin-6-one. In this review, an attempt is made to collate and review the structures of diverse hymenialdisine and related fused-azepinones of synthetic/natural origin and their biological properties.

Methods to Access 2-aminobenzimidazoles of Medicinal Importance

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Benzimidazole (BI) and derivatives are interesting because several of these compounds have been found to have a diversity of biological activities with clinical applications. In view of their importance, the synthesis of BI and its derivatives is still considered as a challenge for synthetic chemists. Examples of compounds used in medicinal chemistry containing BI, as important nucleus, are Astemizole (antihistaminic), Omeprazole (antiulcerative) and Rabendazole (fungicide), some of these compounds have the 2- aminobenzimidazole (2ABI) as base nucleus. The structure of 2ABI derivatives contains a cyclic guanidine moiety, which is interesting because of its free lone pairs, labile hydrogen atoms and planar delocalized structure. The delocalized 10-π electron system and the extension of the electron conjugation with the exocyclic amino group, in 2ABI, making these heterocycles to have amphoteric character. The 2ABI has been used as building blocks for the synthesis of several BI derivatives as medicinally important molecules. On these bases, herein, we present a bibliographic review concerning the recent methodologies used in the synthesis of 2ABIs, including the substituted ones.

Synthesis and biological evaluation of pyrazole linked benzothiazole-β-naphthol derivatives as topoisomerase I inhibitors with DNA binding ability

A series of new pyrazole linked benzothiazole-β-naphthol derivatives were designed and synthesized using a simple, efficient and ecofriendly route under catalyst-free conditions in good to excellent yields. These derivatives were evaluated for their cytotoxicity on selected human cancer cell lines. Among those, the derivatives 4j, 4k and 4l exhibited considerable cytotoxicity with IC₅₀ values ranging between 4.63 and 5.54 µM against human cervical cancer cells (HeLa). Structure activity relationship was elucidated by varying different substituents on benzothiazoles and pyrazoles. Further, flow cytometric analysis revealed that these derivatives induced cell cycle arrest in G2/M phase and spectroscopic studies such as UV-visible, fluorescence and circular dichroism studies showed that these derivatives exhibited good DNA binding affinity. Additionally, these derivatives can effectively inhibit the topoisomerase I activity. Viscosity studies and molecular docking studies demonstrated that the derivatives bind with the minor groove of the DNA.

Heterocycle-based bifunctional organocatalysts in asymmetric synthesis

Different chiral bifunctional organocatalysts derived from trans-cyclohexane-1,2-diamine bearing different types of guanidine units able to form-hydrogen bonding activation have been designed. Conformational rigid 2-aminobenzimidazoles bearing a tertiary amino group have been used in enantioselective Michael type reactions of activated methylene compounds to nitroalkenes. The C2 symmetric bis(2-aminobenzimidazole) derivatives the appropriate organocatalyst for the conjugate addition of 1,3-dicarbonyl compounds to maleimides as well as for the SN1 reaction of benzylic alcohols with carbon nucleophiles. 2-Aminobenzimidazoles bearing a primary amino group have shown excellent catalytic activity in the Michael reaction of aldehydes to maleimides and nitroalkenes. Diastereomeric 2-aminopyrimidines bearing a prolinamide unit have been incorporated in the trans-cyclohexane-1,2-diamine scaffold and have been used for the inter- and intra-molecular direct aldol reaction under solvent-free conditions. For the Michael reaction of aldehydes with maleimides the primary amine 2-aminopyrimidine has shown excellent efficiency as organocatalyst. The bifunctional character of these organocatalysts has been demonstrated by means of DFT calculations.

Novel synthesis of thiazolo/thienoazepine-5,8-diones from dihalo cyclic 1,3-diketones and mercaptonitrile salts

An efficient approach to thiazolo[4,5-b]azepine-5,8-diones and thieno[3,2-b]azepine-5,8-diones has been developed via a domino synthesis of multifunctionalized thiazoles/thiophenes and further intramolecular cyclization.

Selective C-H fluorination of pyridines and diazines inspired by a classic amination reaction

Fluorinated heterocycles are prevalent in pharmaceuticals, agrochemicals, and materials. However, reactions that incorporate fluorine into heteroarenes are limited in scope and can be hazardous. We present a broadly applicable and safe method for the site-selective fluorination of a single carbon-hydrogen bond in pyridines and diazines using commercially available silver(II) fluoride. The reactions occur at ambient temperature within 1 hour with exclusive selectivity for fluorination adjacent to nitrogen. The mild conditions allow access to fluorinated derivatives of medicinally important compounds, as well as a range of 2-substituted pyridines prepared by subsequent nucleophilic displacement of fluoride. Mechanistic studies demonstrate that the pathway of a classic pyridine amination can be adapted for selective fluorination of a broad range of nitrogen heterocycles.

General and mild preparation of 2-aminopyridines

A general and facile one-pot amination procedure for the synthesis of 2-aminopyridines from the corresponding pyridine-N-oxides is presented as a mild alternative to S(N)Ar chemistry. A variety of amines and heterocyclic-N-oxides participate effectively in this transformation which uses the phosphonium salt, PyBroP, as a means of substrate activation.

Trypanothione reductase high-throughput screening campaign identifies novel classes of inhibitors with antiparasitic activity

High-throughput screening of 100,000 lead-like compounds led to the identification of nine novel chemical classes of trypanothione reductase (TR) inhibitors worthy of further investigation. Hits from five of these chemical classes have been developed further through different combinations of preliminary structure-activity relationship rate probing and assessment of antiparasitic activity, cytotoxicity, and chemical and in vitro metabolic properties. This has led to the identification of novel TR inhibitor chemotypes that are drug-like and display antiparasitic activity. For one class, a series of analogues have displayed a correlation between TR inhibition and antiparasitic activity. This paper explores the process of identifying, investigating, and evaluating a series of hits from a high-throughput screening campaign.

Design and synthesis of novel potent and selective integrin alphanubeta3 antagonists--novel synthetic routes to isoquinolinone, benzoxazinone, and quinazolinone acetates

An unexpected ring contraction of benzazepinone based alpha(nu)beta(3) antagonists led to the design of quinolinone-type derivatives. Novel and efficient synthetic routes to isoquinolinone, benzoxazinone, and quinazolinone acetates were established. Nanomolar alpha(nu)beta(3) antagonists based on these new scaffolds were prepared. Moreover, benzoxazinones 15a and 15b exhibited high microsomal stability and good permeability.

Carbodiimide-based benzimidazole library method

Using carbodiimide reagents [1,3-diisopropylcarbodiimide or N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC)], we have developed a mild, generalized, one-pot method that delivers N-2-arylaminobenzimidazole esters from commercially available aryl isothiocyanates and o-phenylenediamines. Following saponification and acidifying, the benzimidazole acids were isolated in overall yields ranging from 75 to 88% from the starting aryl isothiocyanates. Nine benzimidazole acids were converted into a library consisting of 180 benzimidazole amides following EDC coupling with commercially available amines. The National Institute of General Medical Science will dispense these benzimidazole amides to academia groups for pilot scale biomedical studies. Using these mild conditions and environmentally safe reagents, we demonstrated that these pharmaceutically ornate heterocycles can also be constructed on solid support.

Novel potent and selective αvβ3/αvβ5 integrin dual antagonists with reduced binding affinity for human serum albumin

The binding of lead compounds and drugs to human serum albumin (HSA) is a ubiquitous problem in drug discovery since it modulates the availability of the leads and drugs to their intended target, which is linked to biological efficacy. In our continuing efforts to identify small molecule alpha(V)beta(3) and alpha(V)beta(5) dual antagonists, we recently reported indoles 2-4 as potent and selective alpha(V)beta(3)/alpha(V)beta(5) antagonists with good oral bioavailability profile. In spite of subnanomolar binding affinity of these compounds to human alpha(V)beta(3) and alpha(V)beta(5) integrins, high HSA binding (96.5-97.3%) emerged as a limiting feature for these leads. Structure-activity HSA binding data of organic acids reported in the literature have demonstrated that the incorporation of polar groups into a given molecule can dramatically decrease the affinity toward HSA. We sought to apply this strategy by examining the effects of such modifications in both the central core constrain and the substituent beta to the carboxylate. Most of these derivatives were prepared in good yields through a cesium fluoride-catalyzed coupling reaction. This reaction was successful with a variety of nitrogen-containing scaffolds (20, 33, and 43) and selected acetylenic derivatives (16, 19, and 34). Among the compounds synthesized, the 3-[5-[2-(5,6,7,8-tetrahydro [1,8]naphthyridin-2-yl)ethoxy]indol-1-yl]-3-[5-(N,N-dimethylaminomethyl)-3-pyridyl]propionic acid (25) was found to be the most promising derivative within this novel series with a subnanomolar affinity for both alpha(v)beta(3) and alpha(v)beta(5) (IC(50) = 0.29 and 0.16 nM, respectively), similar to our initial lead receptor antagonists 2-4, and exhibiting a low HSA protein binding (40% bound, K(d) = 1.1+/-0.4 x 10(3) microM) and an improved in vitro stability profile toward human and mouse microsomes (99.9% and 98.7% remaining after 10 min). Moreover, the selectivity of 25 toward alpha(5)beta(1) and IIbIIIa integrins was perfectly maintained when compared to the parent leads 2-4. Thus, compound 25 was selected as a new lead with improved drug-like properties for further evaluations in the field of oncology and osteoporosis.

Novel RGD-like molecules based on the tyrosine template: design, synthesis, and biological evaluation on isolated integrins αVβ3/αIIbβ3 and in cellular adhesion tests

RGD (Arg-Gly-Asp) peptidomimetics have been designed for covalent anchorage on biomaterials. The tyrosine template was thus equipped with (i) a basic side chain of various flexibility, (ii) an acidic side chain, which incorporated the XPS fluorine tag, and (iii) a spacer-arm terminated by a primary amine for surface grafting. The most active compounds showed IC50 values in the nanomolar range versus isolated human integrins alphaVbeta3 and alphaIIbbeta3. Preincubation of CaCo2 cells with soluble peptidomimetics (2 and 19a) prevented cellular adhesion on culture plates coated with vitronectin. On the other hand, peptidomimetics (19a and 19b) immobilized on a poly(ethylene)terephthalate membrane (PET) promoted CaCo2 cells adhesion. A modeling study at the ab initio level in MINI-1' basis allowed to compare the various synthetic ligands of integrins and to propose novel pharmacophore structures.