A convenient synthesis of protected (R)-α-phenylproline derivatives using the Mitsunobu reaction

Article abstract of DOI:10.1016/S0040-4020(97)00521-8

Boc-(R)-α-phenylproline ethyl ester 1 was prepared in good yield starting from racemic phenylglycine. Condensation of phenylglycine ethyl ester with benzaldehyde furnished N-benzylidene phenylglycine ethyl ester which was allylated under phase transfer catalysis conditions. After acidic hydrolysis, tile resulting α-allylphenylglycine ethyl ester was enzymatically resolved using PLE. Hydroboration and oxidation of the double bond, Boc-protection and subsequent ring closure using the Mitsunobu reaction protocol gave rise to Boc-(R)-α-phenylproline ethyl ester.