Stereospecific syntheses of (2S,3R) 3-carboxyproline and (2S,3R) 3-ami
noproline are reported which make use of the stereospecific alkylation
of (4S)-N-(t-butyldimethylsilyl)azetidin-2-one 4-carboxylic acid with
the cyclic sulfate derived from ethylene glycol.