Bruno Drouillat

Lithium Triflate as a New Promoter of Glycosylation Under Neutral Conditions 1

Abstract The glycosyl donors 2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl trichloroacetimidate and 3,4,6-tri-O-benzyl-α-D-fucopyranosyl trichloroacetimidate were activated under neutral conditions with a catalytic amount (0.05 equiv) of lithium triflate and reacted with a series of alcohols including an acid sensitive sugar to give the corresponding glycosides in high yields. The stereoselectivity of the glycosylation was improved by introducing a participating group next to the anomeric position. 1. Presented at the French Chemical Society Meeting, Palaiseau, Sept. 1995.

Diastereoselective syntheses of α-amino-β-hydroxyesters precursors of the ribosyl-diazepanone core of the liposidomycins

The diastereoselective syntheses of the O -protected ribosyl-β-hydroxy-α-amino esters 3 and 4 , precursors of α-ribosyl-diazepanone core analogues of the liposidomycins, respectively, from the β-ketoesters 5 and 6 are described. The anti relationship between the two adjacent aminated and hydroxylated carbons was controlled by sequential hydrogenation of the β-ketoesters in the presence of chiral ruthenium catalysts and electrophilic amination of the resulting β-hydroxyesters.

Single and multiple peptide γ-turns: literature survey and recent progress

In contrast to the extensively investigated β-turn conformation in peptides and proteins, single and multiple γ-turns have been much less commonly studied. Single and non-contiguous multiple γ-turns have been relatively often authenticated in small cyclic peptides, but these important peptide main-chain reversal motifs have not been examined carefully either in linear peptides or in globular proteins. This Perspective article summarizes literature data on this aspect of peptide stereochemistry, expanding the discussion also to the rarely found, contiguous multiple γ-turns which generate incipient or fully-developed 2.27-(γ-) helices. Unpublished results of recent research activities on this topic ongoing in our laboratories are also briefly outlined.