Influence of Various Silyl Protecting Groups on Stereoselective 2-Deoxyrhamnosylation

The influence of various silyl protecting groups on 2-deoxyrhamnosylation using 2-deoxyrhamnosyl acetates, thioglycosides, and (p-methoxyphenyl)vinylbenzoate (PMPVB) donors has been presented. C-Glycosylation reactions reveal that tertbutyldimethylsilyl (TBDMS), triisopropylsilyl (TIPS), and tert-butyldiphenylsilyl (TBDPS) silyl protected rhamnosyl oxocarbenium ions have no facial selectivity except for the conformationally (4H3) locked tetraisopropyldisiloxane (TIPDS) protected rhamnose donor, which provides complete alpha-selectivity. However, TBDPS protected rhamnosyl donors are found to be superior protecting groups for alpha-stereoselective O-glycosylation reactions with various acceptors. The observed results are found consistent across donors and donor activation conditions. Most importantly, the study was conducted at room temperature unlike the other energy-intensive low-temperature studies and was bound to have more practical utility. The outcomes have been explained using kinetic and thermodynamic analyses.

Automated summary

This study investigates the influence of different silyl protecting groups (TBDMS, TIPS, and TBDPS) on 2-deoxyrhamnosylation. It is found that the TIPDS protecting group exhibits complete alpha-selectivity in C-glycosylation reactions. In contrast, the TBDPS protecting group shows superior protection for alpha-stereoselective O-glycosylation reactions with various acceptors.