Asymmetric synthesis ofS-alkyl-substituted (R)-cysteinesvia a chiral NiII complex of the Schiff's base of dehydroalanine with (S)-2-N-(N-benzylprolyl)aminobenzophenone
摘要:
An efficient procedure was developed for the asymmetric synthesis of S-alkyl derivatives of (R)-cysteine by nucleophilic addition of alkanethiols ((BuSH)-S-n, (BuSH)-S-t. or tert-C5H11SH) to the C=C bond of the dehydroalanine fragment in the Ni-11 complex of the Schiffs base of Delta-Ala with (S)-2-N-(N-benzylprolyl)aminobenzophenone [(S)-BPB-Delta-Ala]Ni-11. Under conditions of thermodynamic control of the reaction, the diastereomeric excess of the complexes with the (S, R)-configuration was 88-96%. After decomposition of the complexes, ( R)-S-butylcysteine, (R)-S-tert-butylcysteine. and (R)-S-tert-pentylcysteine were isolated with an enantiomeric purity of >97%.