Preparatory Study for the Synthesis of the Starfish Alkaloid Imbricatine. Syntheses of 5-Arylthio-3-methyl-L-histidines.
作者:Masashi OHBA、Takafumi MUKAIHIRA、Tozo FUJII
DOI:10.1248/cpb.42.1784
日期:——
Chiral syntheses of 3-methyl-5-(phenylthio)-L-histidine (8a) and 3-methyl-5-(1-naphthalenylthio)-L-histidine (8b), selected as models for the asteroid alkaloid imbricatine (7), have been accomplished through a 10-step route starting from 4(5)-bromoimidazole (9). The key steps involved were methylation of 9, hydroxymethylation of 4-bromo-1-methyl-1H-imidazole (11), replacement of the 4-bromo group by an arylthio group in the aldehyde 14, and introduction of a chiral α-amino acid moiety into the chlorides 17a and 17b by the "bis-lactim ether" method. The synthesis of the 4-(4-methoxybenzyl)thio analogue 17c, carried out in a similar manner, concluded formal syntheses of ovothiols A and C (1 and 3).
从 4(5)-溴咪唑 (9) 开始,通过 10 步路线完成了 3-甲基-5-(苯硫基)-L-组氨酸 (8a) 和 3-甲基-5-(1-萘硫基)-L-组氨酸 (8b) 的手性合成。其中涉及的关键步骤包括 9 的甲基化、4-溴-1-甲基-1H-咪唑 (11) 的羟甲基化、醛 14 中的芳硫基取代 4-溴基,以及通过 "双-内酯醚 "法将手性 α-氨基酸分子引入氯化物 17a 和 17b。以类似的方法合成了 4-(4-甲氧基苄基)硫代类似物 17c,从而完成了鹅硫醇 A 和 C(1 和 3)的正式合成。