Stereoselectivity Switch in the Trapping of Polar Organometallics with Andersen's Reagent-Access to Highly Stereoenriched Transformable Biphenyls.

The trapping of racemic polar carbometallic species with (-)-menthyl ( SS)- p-toluenesulfinate (Andersen's reagent) typically proceeds with a very low level of resolution. In this paper, we describe a strategy that allows access to highly atropo-enriched and functionalizable biphenyls by means of Andersen's reagent under kinetic resolution conditions. In particular, useful enantiopure 2-iodobiphenyls could be obtained and were employed in a challenging hypervalent iodine-catalyzed oxidation reaction.

Effect of uridine protecting groups on the diastereoselectivity of uridine-derived aldehyde 5'-alkynylation.

The 5'-alkynylation of uridine-derived aldehydes is described. The addition of alkynyl Grignard reagents on the carbonyl group is significantly influenced by the 2',3'-di-O-protecting groups (R1): O-alkyl groups led to modest diastereoselectivities (65:35) in favor of the 5'R-isomer, whereas O-silyl groups promoted higher diastereoselectivities (up to 99:1) in favor of the 5'S-isomer. A study related to this protecting group effect on the diastereoselectivity is reported.

5'-Methylene-triazole-substituted-aminoribosyl uridines as MraY inhibitors: synthesis, biological evaluation and molecular modeling.

The straightforward synthesis of 5'-methylene-[1,4]-triazole-substituted aminoribosyl uridines is described. Two families of compounds were synthesized from a unique epoxide which was regioselectively opened by acetylide ions (for compounds II) or azide ions (for compounds III). Sequential diastereoselective glycosylation with a ribosyl fluoride derivative, Cu(i)-catalyzed azide-alkyne cycloaddition (CuAAC) with various complementary azide and alkyne partners afforded the targeted compounds after final deprotection. The biological activity of the 16 resulting compounds together with that of 14 previously reported compounds I, lacking the 5' methylene group, was evaluated on the MraY transferase activity. Out of the 30 tested compounds, 18 compounds revealed MraY inhibition with IC50 ranging from 15 to 150 µM. A molecular modeling study was performed to rationalize the observed structure-activity relationships (SAR), which allowed us to correlate the activity of the most potent compounds with an interaction involving Leu191 of MraYAA. The antibacterial activity was also evaluated and seven compounds exhibited a good activity against Gram-positive bacterial pathogens with MIC ranging from 8 to 32 µg mL(-1), including the methicillin resistant Staphylococcus aureus (MRSA).

A diastereoselective synthesis of 5'-substituted-uridine derivatives.

A straightforward strategy for the synthesis of 5'-substituted-uridine derivatives is described. It relies on the introduction of various substituents at C-5' at the last step of the synthesis by regioselective nucleophilic opening of a unique epoxide that provides access to a small library of compounds. This epoxide results from the diastereoselective epoxidation, performed at a multigram scale, of a uridine-derived alkene. The configuration of the newly created 5' asymmetric center has been unambiguously assigned by X-ray diffraction analysis.

Toward analogues of MraY natural inhibitors: synthesis of 5'-triazole-substituted-aminoribosyl uridines through a Cu-catalyzed azide-alkyne cycloaddition.

A straightforward strategy for the synthesis of triazole-containing MraY inhibitors has been developed. It involves the sequential introduction of a terminal alkyne at the 5' position of an uridine derivative and O-glycosylation with a protected aminoribose leading to an elaborated alkyne scaffold. An efficient Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) allowed the introduction of chemical diversity toward a small library of inhibitors.

Bacterial Transferase MraY, a Source of Inspiration towards New Antibiotics.

The bacterial resistance to antibiotics constitutes more than ever a severe public health problem. The enzymes involved in bacterial peptidoglycan biosynthesis are pertinent targets for developing new antibiotics, notably the MraY transferase that is not targeted by any marketed drug. Many research groups are currently working on the study or the inhibition of this enzyme. After a concise overview of the role, mechanism and inhibition of MraY, the structure-activity relationships of 5'-triazole-containing aminoribosyluridine inhibitors, we previously synthetized, will be presented. The recently published MraY X-ray structures allowed us to achieve a molecular virtual high-throughput screening of commercial databases and our in-house library resulting in the identification of promising compounds for the further development of new antibiotics.