Synthesis of the 3'-O-sulfated TF antigen with a TEG-N3 linker for glycodendrimersomes preparation to study lectin binding

The synthesis of gram quantities of the TF antigen (β-ᴅ-Gal-(1→3)-α-ᴅ-GalNAc) and its 3'-sulfated analogue with a TEG-N3 spacer attached is described. The synthesis of the TF antigen comprises seven steps, from a known N-Troc-protected galactosamine donor, with an overall yield of 31%. Both the spacer (85%) and the galactose moiety (79%) were introduced using thioglycoside donors in NIS/AgOTf-promoted glycosylation reactions. The 3'-sulfate was finally introduced through tin activation in benzene/DMF followed by treatment with a sulfur trioxide-trimethylamine complex in a 66% yield.

Highly functionalized diaminocyclopentanes: A new route to potent and selective inhibitors of human O-GlcNAcase

A new class of compounds inhibiting de-O-glycosylation of proteins has been identified. Highly substituted diaminocyclopentanes are impressively selective reversible non-transition state O-β-N-acetyl-d-glucosaminidase (O-GlcNAcase) inhibitors. The ease of preparative access and remarkable biological activities provide highly viable leads for the development of anti-tau-phosphorylation agents with a view to eventually ameliorating Alzheimer's disease.

Efficient synthesis of aziridinecyclooctanediol and 3-aminocyclooctanetriol

Cyclooctene endoperoxide was used as the key compound for the synthesis of aziridinecyclooctanediol and 3-aminocyclooctanetriol. Reduction of the cyclooctene endoperoxide, prepared by photooxygenation of cis,cis-1,3-cyclooctadiene, with zinc gave a cyclooctenediol and then benzylation of the hydroxy group yielded dibenzylated cyclooctene. Oxidation of the latter compound by OsO4/NMO followed by mesylation of the hydroxy group provided bis(benzyloxy)cyclooctane-1,2-diyl dimethanesulfonate. Reaction of the bis(benzyloxy)cyclooctane-1,2-diyl dimethanesulfonate with NaN3 gave 2-azido-3,8-bis(benzyloxy)cyclooctyl methanesulfonate. Reduction of the azide group and debenzylation to give an amine provided the new 3-aminocyclooctanetriol. Treatment of the 2-azido-3,8-bis(benzyloxy)cyclooctyl methanesulfonate with Zn/NH4Cl and debenzylation resulted in the target aziridinecyclooctanediol.

Synthesis of Novel Ferrocene-Benzofuran Hybrids via Palladium- and Copper-Catalyzed Reactions

The combination of the ferrocene skeleton with pharmacophores often leads to molecules with interesting biological properties. Five ferrocene-benzofuran hybrids of different structures were synthesized by transition metal catalyzed reactions. The efficiency of both homogeneous and heterogeneous catalytic methods was tested. The products were characterized using 1H, 13C NMR and FTIR spectroscopy, HRMS and cyclic voltammetry. The structure of one of the new compounds was also proved with X-ray crystallography. The new hybrids showed moderate cytotoxicity on MCF-7 and MDA-MB-231 cell lines. It is remarkable that the less curable MDA-MB-231 cell line was more sensitive to treatment with three ferrocene derivatives.

Diaminocyclopentane-derived O-GlcNAcase inhibitors for combating tau hyperphosphorylation in Alzheimer's disease

We developed potent and selective aminocyclopentane-derived inhibitors of human O-N-acetyl-β-D-glucosaminidase (OGA) implicated in Alzheimer's disease. For example compound 13 was a nanomolar OGA inhibitor with 92 000-fold selectivity over human HexB. It was non-toxic and increased protein O-GlcNAcylation in the culture of murine neural cells, showing new alternatives in the treatment of tauopathies.

Total Synthesis via Biomimetic Late-Stage Heterocyclization: Assignment of the Relative Configuration and Biological Evaluation of the Nitraria Alkaloid (±)-Nitrabirine

The racemic total synthesis of nitrabirine (5) together with its previously undescribed epimer 2-epi nitrabirine (5') is accomplished via a six-step route based on a biomimetic late-stage heterocyclization. This allowed the assignment of the relative configuration of nitrabirine by the lanthanide-induced shifts (LIS) experiment, which was later on confirmed by X-ray diffraction of obtained single crystals. Furthermore, oxidation studies demonstrated that the direct N-oxidation of nitrabirine does not yield nitrabirine N-oxide as reported earlier. In contrast, the reaction of hydrogen peroxide with nitrabirine (5) yields the salt 24', whereas 2-epi nitrabirine (5') surprisingly leads to a previously uncharacterized product 22 under the same conditions. Finally, a Fischer indole reaction gave access to novel tetracyclic nitrabirine derivatives 26a-d. A comprehensive biological evaluation of nitrabirine (5), 2-epi nitrabirine (5'), and all derivatives synthesized in this study revealed general biofilm dispersal effects against Candida albicans. Moreover, specific compounds showed moderate antibacterial activities as well as potent cytotoxic activities.

Nanoemulsions as Delivery Systems for Poly-Chemotherapy Aiming at Melanoma Treatment

Aims: Advanced melanoma is characterized by poor outcome. Despite the number of treatments having been increased over the last decade, current pharmacological strategies are only partially effective. Therefore, the improvement of the current systemic therapy is worthy of investigation. Methods: a nanotechnology-based poly-chemotherapy was tested at preclinical level. Temozolomide, rapamycin, and bevacizumab were co-loaded as injectable nanoemulsions for total parenteral nutrition (Intralipid^®), due to suitable devices, and preliminarily tested in vitro on human and mouse cell models and in vivo on the B16-F10 melanoma mouse model. Results: Drug combination was efficiently loaded in the liquid lipid matrix of Intralipid^®, including bevacizumab monoclonal antibody, leading to a fast internalization in tumour cells. An increased cytotoxicity towards melanoma cells, as well as an improved inhibition of tumour relapse, migration, and angiogenesis were demonstrated in cell models for the Intralipid^®-loaded drug combinations. In preliminary in vivo studies, the proposed approach was able to reduce tumour growth significantly, compared to controls. A relevant efficacy towards tumour angiogenesis and mitotic index was determined and immune response was involved. Conclusions: In these preliminary studies, Intralipid^® proved to be a safe and versatile poly-chemotherapy delivery system for advanced melanoma treatment, by acting on multiple mechanisms.

A Highly Efficient Ga(OTf)3/KI-Catalysed Transformation of aryl azides to aryl amines using low catalyst loading

A highly proficient transformation of aryl azides to aryl amines under Ga(OTf)3/KI catalysis is described.

A Simple Glycolipid Mimic of the Phosphatidylinositol Mannoside Core from Mycobacterium tuberculosis Inhibits Macrophage Cytokine Production

Glycolipids from Mycobacterium tuberculosis have a profound impact on the innate immune response of the host. Macrophage-inducible C-type lectin (Mincle) is a pattern-recognition receptor that has been shown to bind trehalose dimycolate (TDM) from the mycobacterium and instigate intracellular signalling in the immune cell. There are structural similarities between the structures of TDM and phosphatidyl inositol mannoside (PIM). We thus hypothesized that these latter structures might also modulate an immune response in a similar manner. To test this, we synthesized a series of new mannose derivatives modified with fatty esters at the 6-position and assessed the release of inflammatory cytokines in human U937 macrophages under the induction of lipopolysaccharides (LPS) after glycolipid treatment. The results showed that the amount of two major cytokines-tumour necrosis factor (TNF)-α and interleukin (IL)-6-released from LPS-stimulated U937 cells decreased significantly when compared to a control upon treatment with the prepared glycolipids, thus indicating a reduction in cytokine production by the macrophages.

A new approach to the synthesis of legionaminic acid analogues

Legionaminic acid is a member of the nonulosonic acids, which are a class of sugars considered to be a virulence factor within a wide variety of pathogenic bacteria. We have developed a synthetic pathway towards C-7 analogues of legionaminic acid starting from Neu5Ac, resulting in the complete synthesis of both legionaminic acid, and its C-7 epimer, from a common precurser. Our approach involves the late-stage introduction of the requisite C-7 nitrogen functionality, thus making our strategy amenable to the introduction of a range of different amide groups at C-7 of legionaminic acid.

We report the synthesis of the bacterial nonulosonic acid legionaminic acid, together with its C-7 epimer, from a common precursor derived from N-acetylneuraminic acid.

Targeting Bile Acid Receptors: Discovery of a Potent and Selective Farnesoid X Receptor Agonist as a New Lead in the Pharmacological Approach to Liver Diseases

Bile acid (BA) receptors represent well-defined targets for the development of novel therapeutic approaches to metabolic and inflammatory diseases. In the present study, we report the generation of novel C-3 modified 6-ethylcholane derivatives. The pharmacological characterization and molecular docking studies for the structure-activity rationalization, allowed the identification of 3β-azido-6α-ethyl-7α-hydroxy-5β-cholan-24-oic acid (compound 2), a potent and selective FXR agonist with a nanomolar potency in transactivation assay and high efficacy in the recruitment of SRC-1 co-activator peptide in Alfa Screen assay. In vitro, compound 2 was completely inactive towards common off-targets such as the nuclear receptors PPARα, PPARγ, LXRα, and LXRβ and the membrane G-coupled BA receptor, GPBAR1. This compound when administered in vivo exerts a robust FXR agonistic activity increasing the liver expression of FXR-target genes including SHP, BSEP, OSTα, and FGF21, while represses the expression of CYP7A1 gene that is negatively regulated by FXR. Collectively these effects result in a significant reshaping of BA pool in mouse. In summary, compound 2 represents a promising candidate for drug development in liver and metabolic disorders.

Liquid-Phase Exfoliation of Graphite into Single- and Few-Layer Graphene with α-Functionalized Alkanes

Graphene has unique physical and chemical properties, making it appealing for a number of applications in optoelectronics, sensing, photonics, composites, and smart coatings, just to cite a few. These require the development of production processes that are inexpensive and up-scalable. These criteria are met in liquid-phase exfoliation (LPE), a technique that can be enhanced when specific organic molecules are used. Here we report the exfoliation of graphite in N-methyl-2-pyrrolidinone, in the presence of heneicosane linear alkanes terminated with different head groups. These molecules act as stabilizing agents during exfoliation. The efficiency of the exfoliation in terms of the concentration of exfoliated single- and few-layer graphene flakes depends on the functional head group determining the strength of the molecular dimerization through dipole-dipole interactions. A thermodynamic analysis is carried out to interpret the impact of the termination group of the alkyl chain on the exfoliation yield. This combines molecular dynamics and molecular mechanics to rationalize the role of functionalized alkanes in the dispersion and stabilization process, which is ultimately attributed to a synergistic effect of the interactions between the molecules, graphene, and the solvent.

Synthesis of novel 13α-18-norandrostane-ferrocene conjugates via homogeneous catalytic methods and their investigation on TRPV1 receptor activation

13α-Steroid-ferrocene derivatives were synthesized via two reaction pathways starting from an unnatural 16-keto-18-nor-13α-steroid. The unnatural steroid was converted to ferrocene derivatives via copper-catalyzed azide-alkyne cycloaddition or palladium-catalyzed aminocarbonylation. 16-Azido- and 16-N-(prop-2-ynyl)-carboxamido-steroids were synthesized as starting materials for azide-alkyne cycloaddition with the appropriate ferrocene derivatives. Based on our earlier work, aminocarbonylation of 16-iodo-16-ene and 16-iodo-15-ene derivatives was studied with ferrocenylmethylamine. The new products were obtained in moderate to good yields and were characterized by (1)H and (13)C NMR, IR and MS. The solid state structure of the starting material 13α-18-norandrostan-16-one and two carboxamide products were determined by X-ray crystallography. Evidences were provided that the N-propargyl-carboxamide compound as well as its ferrocenylmethyltriazole derivative are able to decrease the activation of TRPV1 receptor on TRG neurons.

Synthesis of novel ethyl 1-ethyl-6-fluoro-7-(fatty amido)-1,4-dihydro-4-oxoquinoline-3-carboxylate derivatives and their biological evaluation

A series of novel ethyl 1-ethyl-6-fluoro-7-(fatty amido)-1,4-dihydro-4-oxoquinoline-3-carboxylate derivatives were prepared through multistep synthesis. The key step in the synthesis was to obtain the C-7 fatty amide derivative. The azide was selectively formed at C-7 position using sodium azide at 60°C. Subsequently, the azide was reduced under mild conditions using zinc and ammonium chloride to form the corresponding amine. The synthesized derivatives were further subjected to biological evaluation studies like cytotoxicity against a panel of cancer cell lines such as DU145, A549, SKOV3, MCF7 and normal lung cells, IMR-90 as well as with antimicrobial and antioxidant activities. It was observed that the carboxylated quinolone derivatives with hexanoic (8a), octanoic (8b), lauric (8d) and myristic (8e) moieties exhibited promising cytotoxicity against all the tested cancer cell lines. The results also suggested that hexanoic acid-based fatty amide carboxylated quinolone derivative (8a) exhibited promising activity against both bacterial and fungal strains and significant antibacterial activity was observed against Staphylococcus aureus MTCC 96 (MIC value of 3.9μg/mL). The compound 8a also showed excellent anti-biofilm activity against Staphylococcus aureus MTCC 96 and Bacillus subtilis MTCC 121 with MIC values of 2.1 and 4.6μg/mL, respectively.

Towards inhibitors of glycosyltransferases: A novel approach to the synthesis of 3-acetamido-3-deoxy-D-psicofuranose derivatives

A novel synthetic strategy leading to 3-acetamido-3-deoxy-D-psicofuranose 9 is presented. The latter compound, after some manipulations, was transformed into fully protected 3-acetamido-3-deoxy-D-psicofuranose 11 as a potential substrate for the synthesis of N-acetylglucosaminyltransferase inhibitors designed by computational methods. After the attempted thioglycosylation of 11 with EtSH in the presence of BF3·OEt2, 2-methyloxazoline derivatives 13 and 14 were isolated.

Design and structure activity relationship of tumor-homing histone deacetylase inhibitors conjugated to folic and pteroic acids

Histone deacetylase (HDAC) inhibition has recently emerged as a novel therapeutic approach for the treatment of various pathological conditions including cancer. Currently, two HDAC inhibitors (HDACi) – Vorinostat and Romidepsin – have been approved for the treatment of cutaneous T-cell lymphoma. However, HDACi remain ineffective against solid tumors and are associated with adverse events including cardiotoxicity. Targeted delivery may enhance the therapeutic indices of HDACi and enable them to be efficacious against solid tumors. We showed herein that morphing of folic and pteroic acids into the surface recognition group of HDACi results in hydroxamate and benzamide HDACi which derived tumor homing by targeting folate receptor (FR), a receptor commonly overexpressed in solid tumors. We observed a correlation between the potency of HDAC1 inhibition and cytotoxicity as only the potent pteroate hydroxamates, 11d and 11e, displayed antiproliferative activity against two representative FR-expression cancer cells. Our observation further supports the previous results which suggest that for a drug to be successfully targeted using the FR, it must be extremely potent against its primary target as the FR has a low delivery efficiency.

Copper-catalysed regioselective azidation of arenes by C–H activation directed by pyridine

A novel and efficient copper-catalysed pyridine directed ortho-azidation of arenes has been developed using safe and stable benzotriazole sulphonyl azide as the azidating agent.

Room-temperature Cu(ii)-catalyzed aromatic C–H azidation for the synthesis of ortho-azido anilines with excellent regioselectivity

An efficient synthesis of ortho-aniline derivatives through aromatic C–H azidation catalyzed by Cu(OAc)₂ have been disclosed. The amino group plays an ortho-directing effect in the azidation reactions, regiospecifically affording the mono-azidated derivative as the sole products.

Resolving the chemical nature of nanodesigned silica surface obtained via a bottom-up approach

The covalent grafting on silica surfaces of a functional dendritic organosilane coupling agent inserted, in a long alkyl chain monolayer, is described. In this paper, we show that depending on experimental parameters, particularly the solvent, it is possible to obtain a nanodesigned surface via a bottom-up approach. Thus, we succeed in the formation of both homogeneous dense monolayer and a heterogeneous dense monolayer, the latter being characterized by a nanosized volcano-type pattern (4-6 nm of height, 100 nm of width, and around 3 volcanos/μm(2)) randomly distributed over the surface. The dendritic attribute of the grafted silylated coupling agent affords enough anchoring sites to immobilize covalently functional gold nanoparticles (GNPs), coated with amino PEG polymer to resolve the chemical nature of the surfaces and especially the volcano type nanopattern structures of the heterogeneous monolayer. Thus, the versatile surface chemistry developed herein is particularly challenging as the nanodesign is straightforward achieved in a bottom-up approach without any specific lithography device.

Total synthesis of pactamycin and pactamycate: a detailed account

This article describes synthetic studies that culminated in the first total synthesis of pactamycin and pactamycate and, in parallel, the two known congeners, de-6-MSA-pactamycin and de-6-MSA-pactamycate, lacking the 6-methylsalicylyl moiety. Starting with L-threonine as a chiron, a series of stereocontrolled condensations led to a key cyclopentenone harboring a spirocyclic oxazoline. A series of systematic functionalizations led initially to the incorrect cyclopentanone epoxide, which was "inverted" under solvolytic conditions. Installation of the remaining groups and manipulation of the oxazoline eventually led to pactamycin, pactamycate, and their desalicylyl analogues.

A responsive particulate MRI contrast agent for copper(I): a cautionary tale

A responsive MION-based MRI contrast agent for the detection of copper(I) is presented. Induced agglomeration of azide and acetylene-functionalized magnetite nanoparticles via Cu(I)-catalysed Huisgen cycloaddition leads to significant decrease in longitudinal relaxivity due to the slow exchange of water molecules trapped within the cluster with bulk solvent. Agglomeration leads to an initial two-fold increase followed by a sharp and almost complete loss in transverse relaxivity for clusters larger than 200 nm in size. The decrease in r(2) for clusters reaching the static dephasing regime has two significant implications for particulate responsive MRI contrast agents. First, the maximum increase in r(2) is barely two-fold, second, since r(2) does not increase continuously with increasing cluster size, the r(1)/r(2) ratio cannot be used to determine the concentration of an analyte ratiometrically.

Synthesis of phidianidines A and B

Reaction of a substituted indole-3-acetyl chloride with N-5-azidopentyl-N'-hydroxyguanidine generated a substituted 3-(5-azidopentylamino)-5-((indol-3-yl)methyl)-1,2,4-oxadiazole. Reduction of the azide with zinc and ammonium formate afforded the amine, which was elaborated to the guanidine, completing short and efficient syntheses of the cytotoxic natural products phidianidines A and B in 19% overall yield by a convergent route that will make analogues readily available for biological evaluation. Initial screening in the NCI 60 cell line at 10(-5) M indicated that the bromine on the indole is necessary for activity and that the amine precursor to phidianidine A is more potent than phidianidine A.