Glycosyl Formates: Glycosylations with Neighboring-Group Participation

Abstract

Protected 2-O-benzyolated glycosyl formates were synthesized in one-step from the corresponding orthoester using formic acid as the sole reagent. Glucopyranosyl, mannopyranosyl and galactopyranosyl donors were synthesized and their glycosylation properties studied using model glycosyl acceptors of varied steric bulk and reactivity. Bismuth triflate was the preferred catalyst and KPF6 was used as an additive. The 1,2-trans-selectivities resulting from neighboring-group participation were excellent and the glycosylations were generally high-yielding.

Synthesis of Superarmed Thioglycosides via the Ring Opening of 1,2-Orthoesters

“…2 Their popularity has been notable in the advent of one-pot glycosylation procedures which draw on the armed-disarmed strategy 3 to instigate sequential activation of donors. 4 'Superarmed' thioglycoside donors can be achieved through a combination of electrondonating benzyl groups and anchimeric assistance of a 2-O-acyl group, the latter necessitating 1,2-trans stereochemistry of the donor. 5 The combination of effects leads to increased reactivity and preferential activation over traditional armed donors.…”