Dependency of the regio- and stereoselectivity of intramolecular, ring-closing glycosylations upon the ring size.

ABSTRACT: Phenyl 3,4,6-tri-O-benzyl-2-O-(3-carboxypropionyl)-1-thio-β-D-galactopyranoside (1) was condensed via its pentafluorophenyl ester 2 with 5-aminopentyl (4a), 4-aminobutyl (4b), 3-aminopropyl (4c) and 2-aminoethyl 4,6-O-benzylidene-β-D-glucopyranoside (4d), prepared from the corresponding N-Cbz protected glucosides 3a-d, to give the corresponding 2-[3-(alkylcarbamoyl)propionyl] tethered saccharides 5a-d. Intramolecular, ring closing glycosylation of the saccharides with NIS and TMSOTf afforded the tethered β(1→3) linked disaccharides 6a-c, the α(1→3) linked disaccharides 7a-d and the α(1→2) linked disaccharide 8d in ratios depending upon the ring size formed during glycosylation. No β(1→2) linked disaccharides were formed. Molecular modeling of saccharides 6-8 revealed that a strong aromatic

SUBMITTER: Claude P 

PROVIDER: S-EPMC3252864 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature