Methyl (R)-cysteinate (2) is converted into methyl (S)-thiirancarboxylate (4) by sodium nitrite and hydrochloric acid; under corresponding conditions (R)-cysteine (3) affords a 3:1 mixture of (R)-thiirancarboxylic acid (12) and the (S)-enantiomer (5).
                                    亚硝酸钠和
盐酸将(R)-半胱
氨酸甲酯(2)转化为(S)-
噻喃甲酸甲酯(4);在相应的条件下,(R)-半胱
氨酸(3)得到(R)-
噻喃羧酸(12)和(S)-对映异构体(5)的3∶1混合物。