Diastereofacial selection in the 1,2-addition of MeMgX and MeLi to 4-oxo sugar: Efficient synthesis of 4-C-methyl-1-S-beta-D-gluco- and galactopyranoside building blocks of moenomycin

The stereochemical course of the 1,2-addition upon treatment of various 1-t hio-4-oxo sugars with MeMgX and MeLi has been determined. The effects of re agent, solvent, and neighboring functionalities in the gluco/galacto (non-c helation/chelation controlled) product distribution are detailed. Stereocon trolled 1,2-addition to these 4-oxo sugars provide access to a number of di fferently functionalized F unit building blocks of the moenomycin family, a nd demonstrate the versatility of this transformation. (C) 1999 Elsevier Sc ience Ltd. All rights reserved.