The synthesis and resolution of N-(benzyloxycarhony1)-y, y-di-tert- butyl-d, ly- carboxyglutamic acid (5a) is described. Resolution using quinine allowed separation of the D enantiomer from the racemic mixture in 15% yield from N-(benzyloxycarbonyl)-0-tosyl-d, l- serine methyl ester (la). Liberation of the L enantiomer from the remaining oily quinine salt followed by purification of the L-tyrosine hydrazide salt of 5a provided an overall yield of ...
[Davies, John S.; Enjalbal, Christine; Nguyen, Corrine; Al-Jamri, Loai; Naumer, Christian Journal of the Chemical Society, Perkin Transactions 1, 2000 , # 17 p. 2907 - 2915]