A concise diastereoselective synthesis of (2S,3S,4R)-3,4-dihydroxyglutamic acid

A concise diastereoselective synthesis of (2S,3S,4R)-3,4-dihydroxyglutamic acid, one of eight possible stereoisomers of 3,4-dihydroxyglutamic acids, is described. The key reaction in this synthesis is stereoselective cyanation of an optically active N-acyliminium intermediate derived from l-tartaric acid with tributyltin cyanide.