光学活性Prolineの合成

抄録

Diazatation of L-ornithine (L-I) in diluted sulfuric acid produces L-2-hydroxy-5-amino-n-valeric acid (L-III), whose configuration being L-ornithine. However, the corresponding 5-hydroxy compound is not prepared by the reaction. Different mechanisms of the reactions was found between L-2-hydroxy-5-p-toluenesulfoamido-n-valeric acid ethyl ester (L-V) obtained from L-III and various kinds of chlorination agents. Namely, the reaction of L-V with thionyl chloride-pyridine at 65∼70°C affords D-2-chloro-5-p-toluenesulfoamido-n-valeric acid ethyl ester (D-VI) as a result of normal SN₂-type substitution reaction, whereas the reaction of L-V with phosphorous pentachloride produces D-N-(p-toluenesulfonyl)proline ethyl ester (D-VII) below 0°C as a result of SN₂-type intramolecular substitution reaction. Furthermore, a mixture of D-VI and D-VII is obtained by the reaction of L-V with phosphorous pentachloride at 65∼70°C in spite of the presence or the absence of catalysts. L-VII is easily synthesized by the cyclization of D-VI in a basic midium. The corresponding L-proline (L-VIII) and D-proline (D-VIII) are obtained by the hydrolysis of L-VII and D-VII, respectively.