A Large-Scale Preparation of (3S,4S)-3-(tert-Butoxycarbonyl)amino-4-methylpyrrolidine and Its Analogs from L-Aspartic Acid.
作者:Toshihiko YOSHIDA、Makoto TAKESHITA、Hitomi ORITA、Noriyuki KADO、Shingo YASUDA、Hideo KATO、Yasuo ITOH
DOI:10.1248/cpb.44.1128
日期:——
(3S, 4S)-3-(tert-Butoxycarbonyl)amino-4-methylpyrrolidine (12a) was synthesized from L-aspartic acid (4) on a large scale. Methylation of dimethyl (2S)-N-benzyl-N-(9-phenylfluoren-9-yl)aspartate (5), easily derived from 4, with methyl iodide gave (3R)-3-methylaspartate (6a) in 91% yield with high diastereoselectivity. Reduction of 6a with lithium aluminum hydride, followed by hydrogenolysis, protection with di-tert-butyl dicarbonate, and mesylation gave 10a in 89% overall yield. Subsequently, reaction of 10a with benzylamine under a nitrogen atmosphere at room temperature, followed by hydrogenolysis, gave the target compound (12a) in 65% overall yield. In a similar manner to that described for the preparation of 12a from 5, compound 5 was converted into 4-ethyl and 4-propyl derivatives (12b, c) in 34% and 38% overall yields.
(3S,4S)-3-(叔丁氧羰基)氨基-4-甲基吡咯烷(12a)由 L-天冬氨酸(4)大规模合成。用碘甲烷将从 4 中容易得到的(2S)-N-苄基-N-(9-苯基芴-9-基)天冬氨酸二甲酯(5)甲基化,得到(3R)-3-甲基天冬氨酸(6a),收率为 91%,非对映选择性高。用氢化铝锂还原 6a,然后进行氢解、二碳酸二叔丁酯保护和甲磺酰化反应,得到了总收率为 89% 的 10a。随后,10a 与苄胺在室温氮气环境下反应,然后进行氢解,得到目标化合物(12a),总收率为 65%。按照类似于从 5 制备 12a 的方法,化合物 5 被转化为 4-乙基和 4-丙基衍生物(12b、c),总产率分别为 34% 和 38%。