The stabilizing effect of the 6-methoxyl or 6-hydroxyl substituent on dehydropeptidase I sensitivity of PS 5 was examined by a new total synthesis of 6-methoxy-epi-PS 5 and 6-hydroxy-epi-PS 5 from dimethyl benzyloxycarbonylaminomalonate. The Wittig reaction of α-(t-butoxycarbonyl)propylidenetriphenylphosphorane with a pyrrolidine derivative predominantly afforded a trans-α,β unsaturated ester, which was epoxidated, N-deprotected and cyclized to give a bicyclic carbapenam with a C-6 hydroxyl group. After the 6-hydroxyl group was methylated, the 2-(acetamido)ethylthio side chain was introduced at C-3 of the carbapenam by benzeneselenenylation of the geminal diester, followed by elimination of the seleninyl group. The resulting carbapenam was converted to 6-methoxy-epi-PS 5. Furthermore, 6-hydroxy-epi-PS 5 was synthesized by the use of tetrahydropyranyl and trimethylsilyl ethers for protection of the 6-hydroxyl group in a process similar to that for synthesis of 6-methoxy-epi-PS 5.
通过从二甲基苄氧基羰基
氨基
丙二酸二甲酯全合成6-甲氧基-epi-PS 5 和6-羟基-epi-PS 5 来检验6-甲氧基或6-羟基取代基对PS 5 脱氢肽酶I敏感性的稳定作用。 α-(叔丁氧基羰基)亚丙基三苯基正膦与
吡咯烷衍
生物的Wittig反应主要产生反式-α,β不饱和酯,将其环氧化、N-脱保护并环化,得到具有C-6羟基的双环碳青霉烯。 6-羟基甲基化后,通过偕二酯的苯
硒基化在碳青霉烯的C-3处引入2-(乙酰胺基)乙
硫基侧链,然后消除
硒基。所得碳青霉烯被转化为 6-甲氧基-epi-PS 5。此外,通过使用
四氢吡喃基和三甲基甲
硅烷基醚来保护 6-羟基,其过程类似于 6-羟基-epi-PS 5 的合成过程。 6-甲氧基-epi-PS 5的合成。