Synthesis of a C-glycoside analogue of beta-D-galactosylthreonine.

A C-linked analogue of beta-D-galactosylthreonine has been prepared from 2,3,4,6-tetra-O-benzyl-D-galactopyranolactone (1) in 14 steps. Three stereogenic centers were created during the synthesis, with the anomeric center of the C-glycoside being generated first by addition of a Grignard reagent to 1 and subsequent reduction of the intermediate hemiacetal with triethylsilane. The two stereogenic centers in the threonine moiety were both established by alkylation of Evans' chiral N-acyloxazolidinone enolates.