Portal de Periódicos da CAPES

Transesterification during glycosylation promoted by silver trifluoromethanesulfonate

1990; Wiley; Volume: 1990; Issue: 6 Linguagem: Inglês

10.1002/jlac.1990199001115

0170-2041

Thomas Ziegler, Pavol Kováč, Cornelis P.J. Glaudemans,

Enzyme Production and Characterization

Abstract 2‐ O ‐[2,2,2‐D 3 ]Acetyl‐3,4,6‐tri‐ O ‐acetyl‐α‐ D ‐galactopyranosyl bromide ( 3 ) was prepared and used as the glycosyl donor in studying the silver trifluoromethanesulfonate‐promoted reaction with methyl 2,3,4‐tri‐ O ‐benzoyl‐β‐ D ‐galactopyranoside ( 4 ) and methyl 2,4,6‐tri‐ O ‐benzoyl‐β‐ D ‐galactopyranoside ( 7 ). In addition to the expected β‐linked disaccharides, methyl 6‐ O ‐[2,2,2‐D 3 ]acetyl‐2,3,4‐tri‐ O ‐benzoyl‐β‐ D ‐galactopyranoside ( 6 ) and methyl 3‐ O ‐[2,2,2‐D 3 ]acetyl‐2,4,6‐tri‐ O ‐benzoyl‐β‐ D ‐galactopyranoside ( 9 ), respectively, were formed. The latter compounds were isolated from the reaction mixture and their structures were confirmed based on spectral data. Thus, it has been proven that, with fully acetylated glycosyl halides as glycosyl donors, in silver trifluoromethanesulfonate‐promoted couplings, O ‐acetylation of the nucleophile occurs as a side reaction, the acetyl group involved originating from position 2 of the glycosyl halide.