Wittig Reaction with N-Protected 3-(Triphenylphosphonio) alaninates: Synthesis of Optically Active (E)-(2-Arylvinyl) glycine Derivatives.
作者:Taisuke ITAYA、Takehiko IIDA、Shigeyuki SHIMIZU、Akemi MIZUTANI、Masatoshi MORISUE、Yasushi SUGIMOTO、Michiko TACHINAKA
DOI:10.1248/cpb.41.252
日期:——
(R)-[2-Carboxy-2-[(methoxycarbonyl)amino]ethyl]triphenylphosphonium chloride (1) was converted by treatment with anion exchange resin (HCO-3) into the inner salt 13h, which gave a better yield (43%) than 1 in the Wittig reaction with benzaldehyde to afford the [S-(E)]-(2-phenylvinyl)glycine derivative 24. The inner salt 13i bearing an N-benzyloxycarbonyl group was prepared by hydrogenolysis of (R)-[3-benzyloxy-2-[(benzyloxycarbonyl)amino]-3-oxopropyl]triphenylphosphonium chloride (11e) over palladium on carbon, followed by dehydrochlorination. Hydrogenolysis of 11e over Pearlman's catalyst afforded the unprotected phosphonium chloride 12 (X=Cl). N-tert-Butoxycarbonylation of 12 followed by dehydrochlorination afforded 13j, which was more efficiently prepared through hydrogenolysis of (R)-[3-benzyloxy-2-[(tert-butoxycarbonyl)amino]-3-oxopropyl]triphenylphosphonium chloride (11f).The usefulness of 13h-j as building blocks for the synthesis of configurationally labile (2-arylvinyl)glycine derivatives was exemplified by the Wittig reactions with piperonal, which exclusively afforded the (E)-isomers 18h-j with high optical purity in 28-39% yield.
(R)-[2-羧基-2-[(甲氧基羰基)氨基]乙基]三苯基氯化鏻(1)经阴离子交换树脂(HCO-3)处理后转化为内盐 13h,在与苯甲醛的 Wittig 反应中,该内盐的产率(43%)优于 1,从而得到[S-(E)]-(2-苯基乙烯基)甘氨酸衍生物 24。带有 N-苄氧羰基的内盐 13i 是通过在碳上钯上氢解 (R)-[3-苄氧基-2-[(苄氧羰基)氨基]-3-氧代丙基]三苯基氯化鏻(11e),然后脱氢氯化制备的。在珀尔曼催化剂上氢解 11e,得到未保护的氯化磷 12(X=Cl)。通过氢解 (R)-[3-苄氧基-2-[(叔丁氧基羰基)氨基]-3-氧代丙基]三苯基氯化鏻 (11f),可以更有效地制备 13j。13h-j 作为合成构型易变的 (2- 芳基乙烯基)甘氨酸衍生物的构筑基块,与胡椒醛的 Wittig 反应证明了其有用性,该反应以 28%-39% 的收率独家获得了高光学纯度的 (E) 异构体 18h-j。