Synthesis of the methyl ethers of methyl 6-deoxy-3-C-methyl-alpha-L-talopyranoside and -alpha-L-mannopyranoside. Examination of the conformation and chromatographic properties of the compounds

By synthesizing each of the methyl ethers of methyl 6-deoxy-3-C-methyl-alpha-L-talopyranoside (17) and -alpha-L-mannopyranoside (35), evidence was obtained that the 6-deoxy-3-C-methyl-2,4-di-O-methyl-alpha-L-mannopyranosyl unit is a building block of the pentasaccharide-containing antigen of the serovariant 19 of M. avium. Based on the H-1 and C-13 NMR spectra of the synthesized methyl ethers, all of the L-mannopyranosyl derivatives and the mono- and disubstituted L-talopyranosyl analogues adopt a C-1(4) conformation, but for each of the persubstituted talopyranosyl sugars the C-4(1) conformation is the most favoured. The TLC and HPLC mobilities of the mannopyranoside derivatives are dependent on the degree of substitution, however in the case of the talose sugars presumably the shape of the molecules, and the strong intramolecular hydrogen bondings are the factors determining the chromatographic behaviour.