Stereoselective preparation of beta-C-glycosides has been developed from acetylated glycopyranosyl 2-pyridyl sulfones, involving a samarium-Barbier coupling procedureoxidation-isomerization sequence.

Carbohydrate Conformation↗

PubMed1998

Stereocontrolled Synthesis of alpha-C-Galactosamine Derivatives via Chelation-Controlled C-Glycosylation.

The samarium diiodide-promoted reduction of 2-deoxy-2-acetamidogalactosyl pyridyl sulfone alpha-5 with ketones or aldehydes under Barbier conditions led unexpectedly to the stereoselective synthesis of alpha-C-galactosamine derivatives in good yields. With carbonyl substrates, alpha:beta selectivities ranged from 20:1 to 5:1, and with aldehydes a stereoselectivity of approximately 5:1 was observed at C7 in favor of the S-isomer. The stereochemical preference of these C-glycosylation reactions is explained by the intermediacy of an alpha-oriented anomeric glycosyl samarium(III) compound that is stabilized via chelation of the metal ion to the C2-acetamido group.

Journal Article↗

PubMedDate not supplied

Two galactosyltransferases' selection of different binders from the same uridine-based dynamic combinatorial library.

Explore the source record for details and available documents.

Carbohydrate Sequence↗