Galabiosyl donors; efficient synthesis from 1,2,3,4,6-penta-O-acetyl-beta-D-galactopyranose

1,2,3,4,6-Penta-O-acetyl-beta-D-galactopyranose was transformed into phenyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D-galactopyranoside (5) and 4-methoxyph enyl 2,3,6-tri-O-benzoyl-beta-D-galactopyranoside (8) in 73% (two steps) an d 58% (three steps) yield, respectively. Glycosylation of the acceptor 8 wi th donor 5 using N-iodosuccinimide-trimethylsilyl trifluoromethanesulfonate as promoter furnished the galabioside 9 (8.8 g) in 95% yield. Further tran sformations provided in high yields anomerically-activated galabiosides (th ioglycoside (1), trichloroacetimidate (2), and bromo-sugar (3)) suitable fo r use as glycosyl donors in syntheses of galabiose-containing oligosacchari des. Several of the compounds reported here are crystalline, which greatly simplified purifications. (C) 2000 Elsevier Science Ltd. All rights reserve d.