New amino acids derived from L-pyroglutamic acid: Synthesis of trans-4- benzyl-cis-5-phenyl-L-proline, L-α-(2-benzyl-3-phenylpropyl)-glycine and L- α-(3-phenylpropyl)-glycine

Article abstract of DOI:10.1016/S0040-4020(97)10399-4

A convenient synthesis of three new amino acids, L-α-(3-phenylpropyl)- glycine, L-α-(2-benzyl-3-phenylpropyl)-glycine and its conformationally constrained analog, trans-4-benzyl-cis-5-phenyl-L-proline is reported. All compounds were prepared in good diastereomeric or enantiomeric purity from L- pyroglutamic acid. Trans-4-benzyl-cis-5-phenyl-L-proline was prepared by benzylation of Boc-L-Pyr-OBn, ring opening with phenyllithium and subsequent cyclisation. Hydrogenolysis under mild conditions then furnished L-α-(2- benzyl-3-phenylpropyl)-glycine. In a similar way, L-α(3-phenylpropyl)- glycine was prepared from cis-5-phenyl-L-proline by catalytic hydrogenolysis.