Luc Demange

Practical synthesis of Boc and Fmoc protected 4-fluoro and 4-difluoroprolines from trans-4-hydroxyproline

Abstract Boc- cis -4-fluoro-L-proline and 4-difluoro-L-proline, usable in classical peptide synthesis, were obtained in respectively 71% (3 steps) and 65% (4 steps) overall yields from the readily available trans -4-hydroxy-L-proline methyl ester. The corresponding fluorinated trans -isomer was isolated in 24% yield (5 steps). Transformation of Boc-protected compounds to their Fmoc-equivalents was performed in high yields.

Synthesis of optically pure N-Boc-protected (2R,3R)- and (2R,3S)-3-fluoroprolines

Abstract Non-protein amino acids (2 R ,3 R )- and (2 R ,3 S )-3-fluoroprolines were synthesized as novel probes for studying the cis / trans isomerization of the amino acylue5f8proline peptide bond. The N -Boc-protected target compounds were obtained as optically pure material starting from (2 S ,3 S )-3-hydroxyproline.

Synthesis and anti-cancer activities of new sulfonamides 4-substituted-triazolyl nucleosides

Nucleoside analogues are among the most known drugs commonly used in antiviral and anticancer chemotherapies. Among them, those featuring a five-membered ring nucleobase are of utmost interest such as the anti-cancer agent AICAR or the anti-viral drug ribavirin. Despite its low activity in vitro in different cell lines, AICAR is under clinical development for several pathologies, thanks to its original mode of action. Indeed, AICAR induced autophagy cell death and is able, following this mechanism, to circumvent resistance to apoptotic drugs including kinase inhibitors currently on the market. To improve the activity of AICAR, we report herein an efficient synthesis of new series of sulfonamide-4-substituted-1,2,3-triazolyl nucleosides using a Cu-catalyzed 1,3-dipolar cycloaddition. All these molecules have been fully characterized and evaluated against two aggressive tumor cell lines, RCC4 and MDA-MB-231. Among them, nucleoside analogue 5i belonging to the ribose series was found to be 19 to 66-fold more active than AICAR. Western blot analyses on RCC4 cells showed that 5i displayed an interesting mode of action by inducing both apoptosis and autophagy cell death, making therefore this class of molecules highly promising for further hit-to-lead optimization.

Interaction of human cyclophilin hCyp-18 with short peptides suggests the existence of two functionally independent subsites

The binding of peptides, derived from the model substrate Suc‐Ala‐Ala‐Pro‐Phe‐pNA, to the human cyclophilin hCyp‐18 was investigated. HCyp‐18 is able to bind 2–4‐mer peptides as well as shorter para‐nitroaniline (pNA) derivatives and pNA surrogates. Although Suc‐Ala‐Phe‐pNA binds hCyp‐18, only proline‐containing peptides are able to block efficiently the peptidyl‐prolyl cis/trans isomerase activity. Competition experiments strongly suggest the existence of two independent subsites: a S1′ ‘proline’ subsite and a S2′–S3′ ‘pNA’ subsite. The interaction at S2’–S3’ requires either a Phe‐pNA C‐terminus or a Phe‐pNA surrogate bearing an H‐bond acceptor able to bind Trp121 and Arg148 simultaneously.

Synthesis of phosphinic alanyl-proline surrogates Alaψ(PO2R-CH)Pro as potential inhibitors of the human cyclophilin hCyp-18

Abstract Pseudopeptides containing the phosphinic analogue of the alanyl-proline motif Alaψ(PO 2 R-CH)Pro, were synthesized via three- (R=H) and four-step (R=CH 3 ) procedures. The mixtures of diastereomers were evaluated as inhibitors of the human cyclophilin hCyp-18, an important peptidyl-prolyl isomerase.

NRPa-308, a new neuropilin-1 antagonist, exerts in vitro anti-angiogenic and anti-proliferative effects and in vivo anti-cancer effects in a mouse xenograft model

Neuropilin-1 (NRP-1) is an extra-cellular receptor for the main Vascular Endothelial Growth Factor over-expressed in tumour tissues, VEGF-A165. Consequently, NRP-1 is involved in angiogenesis and in tumour growth, and its over-expression is related to a clinical poor prognosis. NRP-1 appears as a major target in oncology, which remains poorly exploited. Herein, we report a new series of 18 small-sized fully organic VEGF-A165/NRP-1 antagonists (NRPas). These compounds share an original scaffold, including two linkers (sulphonamide and amide) and three aromatic cores. Among them, 2a (renamed NRPa-308) emerges as a promising hit. Inxa0vitro,2a exerts not only potent anti-angiogenic activity, but also significant effects on cell viability of large panel of human solid and haematological cancer cell lines. Importantly, 2a is less cytotoxic on healthy tissues than the marketed anti-angiogenic drug sunitinib. Lastly, in a mouse xenograft model (human MDA-MB-231 breast cancer cells), 2a improves the median survival and reduces the tumour growth, but does not exert visible acute toxicity. Altogether, these results highlight its huge potential for a further hit-to-lead optimization, leading to new anti-cancer drugs.

Synthesis of pseudopeptides containing aza-phenylalanine surrogates of the Phe-pNA motif: Influence on the binding to the human cyclophilin hCyp-18

Tripeptides bearing aza-phenylalanine derivatives Aphe-X-(4-nitrophenyl),where X is CH2, O or NH, were synthesized starting from benzylhydrazine via a 4-step strategy. The pseudopeptides were evaluated as ligands of cyclophilin hCyp-18, an important human peptidyl-prolyl isomerase (PPIase). All pseudopeptides bind to hCyp-18, although only Suc-Ala-Pro-Phe-pNA 11 and Suc-Ala-Pro-Aphe-pNB (X = CH2) 4 are able to inhibit the PPIase activity, suggesting that they can bind to the S1–S1′ and S2′–S3′ subsites of hCyp-18 simultaneously. A circular dichroism study showed that only compounds 4 and 11 have β-turns conformations in 0.47 M LiCl/TFE (which favors a cis-Ala-Pro conformation). In addition, the hydrazide (X = CH2) 4 as well as the aza-urea (X = NH) 6 are resistant to both trypsin and alpha-chymotrypsin. The corresponding carbazate (X = O) 10 readily reacts with alpha-chymotrypsin and is also hydrolyzed by trypsin.

Ultrasound-assisted facile one-pot sequential synthesis of novel sulfonamide-isoxazoles using cerium (IV) ammonium nitrate (CAN) as an efficient oxidant in aqueous medium

A series of novel 3,5-disubstituted isoxazoles have been synthesized, using a new, green, and versatile one-pot three-steps methodology. The key step is an oxidative 1,3-dipolar cycloaddition under ultrasonic irradiation, occurring in aqueous media, and mediated by cerium (IV) ammonium nitrate (CAN). CAN is a one-electron oxidant, highly soluble in water, slightly toxic and inexpensive, that allows the in situ conversion of the intermediate aldoximes into nitrile oxide. The syntheses are highly regioselective, as illustrated by the structures of the final compounds, which have been fully assessed by spectral analyses (1H and 13C NMR, MS). This study illustrates the potency of the ultrasound activation to synthesize a set of highly functionalized heterocycles, with potential applications in biology, in short reaction times and following an eco-friendly process.

Modular synthesis of new C -aryl-nucleosides and their anti-CML activity

The C-aryl-ribosyles are of utmost interest for the development of antiviral and anticancer agents. Even if several synthetic pathways have been disclosed for the preparation of these nucleosides, a direct, few steps and modular approaches are still lacking. In line with our previous efforts, we report herein a one step - eco-friendly β-ribosylation of aryles and heteroaryles through a direct Friedel-Craft ribosylation mediated by bismuth triflate, Bi(OTf)3. The resulting carbohydrates have been functionalized by cross-coupling reactions, leading to a series of new C-aryl-nucleosides (32 compounds). Among them, we observed that 5d exerts promising anti-proliferative effects against two human Chronic Myeloid Leukemia (CML) cell lines, both sensitive (K562-S) or resistant (K562-R) to imatinib, the gold standard of care used in this pathology. Moreover, we demonstrated that 5d kills CML cells by a non-conventional mechanism of cell death.

Concise synthesis and antibacterial evaluation of novel 3-(1,4-disubstituted-1,2,3-triazolyl)uridine nucleosides

We report herein a simple and efficient synthesis of a new series of antibacterial uridine nucleosides. The strategy involved a sequential silylation/N‐glycosylation/N‐propargylation procedure of uracil 1 for preparing the dipolarophile 5 in good yield. A series of novel uridine‐[1,2,3]triazole nucleosides 6a–j were efficiently synthesized via the copper‐catalyzed azide–alkyne cycloaddition (CuAAC) from dipolarophile 5 with different selected azides. The reactions were carried out under both conventional and ultrasonic irradiation conditions. In general, improvements were observed when reactions were carried out under sonication. Their antibacterial potential has been evaluated by means of a micro‐dilution assay against either Gram‐positive or Gram‐negative bacteria. Compounds 6i and 6j have shown significant bactericidal activity against Staphylococcus aureus (MICu2009=u200910 and 6u2009μM, respectively), and 6h against Escherichia coli (MICu2009=u20098u2009μM). Moreover, antibacterial kinetic assays showed that 6i and 6j significantly reduced the S. aureus growth rate at the MIC concentration, after 6u2009h, compared to their deprotected analogs, 6k and 6l, respectively. Compound 6h also significantly reduced the growth of E. coli. These antibacterial effects may be related to the penetrating properties of these compounds, as revealed by the leakage of nucleic acids from the sensitive strains.