Asymmetric synthesis of orthogonally protected (2S,4R)- and (2S,4S)-4-hydroxyornithine

Synthesis of orthogonally protected (2S,4R)- and (2S,4S)-4-hydroxyornithines I is reported featuring an asym. alkylation of N-(diphenylmethylene)glycine tert-Bu ester with (5S)-N-benzyloxycarbonyl-5-iodomethyl oxazolidine. Double stereoselection was examd. using chiral ammonium salts as phase transfer catalysts, and a substrate-directed chiral induction is documented. [on SciFinder (R)]