Thia-analogues of amino acids synthesis of peptide derivatives containing 3-thia-analogues of amino acids.

N-Protected dipeptides containing L-3-thia-analogues of phenylalanine, p-nitro-phenylalanine, lysine and leucine respectively were prepared applying an enantioselective enzymatic reaction step. Racemic synthetic intermediates of the type acyl-NH-CH(R(1))-CO-D,L-NH-CH(S-R(2))-COOBzl were selectively deprotected at the C-terminus by enzymatic hydrolysis using thermitase or trypsin.