A concise approach to homochiral 3,4-dihydroxyglutamic acids

A concise diastereoselective synthesis of 3,4-dihydroxyglutamic acids was investigated. The key reaction in this synthesis is stereoselective cyanation of an optically active N-acyliminium intermediate derived from l- or d-tartaric acid. The stereoselectivity in the cyanation reaction could be controlled by the protective group of the hydroxyl function. Deprotection of the obtained cyanolactam followed by acidic hydrolysis afforded the desired 3,4-dihydroxyglutamic acids. The 3,4-dihydroxyglutamic acids obtained in this synthesis are (2S,3S,4R)-, (2R,3S,4R)-, (2S,3R,4S)-, and (2R,3R,4S)-isomers and the three latter compounds are novel derivatives of glutamic acids.