An n.m.r. and conformational analysis of the terminal trisaccharide from the serologically active glycolipid of Mycobacterium leprae in different solvents

Abstract

The 1H- and 13C-n.m.r. spectra of allyl 2- O-[4- O-(3,6-di- O-methyl-β- d-glucopyranosyl)-2,3-di- O-methyl- a- l-rhamnopyranosyl]-3- O-methyl- a- l- rhamnopyranoside ( 3), a glycoside of the terminal trisaccharide found in the phenolic glycolipid I from Mycobacterium leprae, and those of the two component disaccharides, allyl 4- O-(3,6-di- O-methyl-β- d-glucopyranosyl)-2,3-di- O-methyl- a- l-rhamnopyranoside ( 1) and allyl 2- O-(2,3-di- O-methyl- a- l-rhamnopyranosyl)-3- O-methyl- a- l-rhamnopyranoside ( 2) have been assigned completely by 1D and 2D techniques. The preferred conformations, determined by chemical shift and n.O.e. studies, were different in D 2O, CD 3OD, and CDCl 3. The preferred conformation of 3 accorded with the results of hard-sphere exo-anomeric (HSEA) calculations.