Pyrrolizidine Alkaloids. The Synthesis and Absolute Configuration of All Stereoisomers of 4-Carboxy-4-ethyl-3-hydroxy-2-isopropyl-4-butanolide, the Necic Acid Component of Axillaridine
作者:Takashi Matsumoto、Hiromitsu Terao、Natsuki Ishizuka、Shuji Usui、Hiroshi Nozaki
DOI:10.1246/bcsj.65.1761
日期:1992.7
γ-lactone acids 4b (2R,3R,4R), 5b and 5a. Subsequently, (E)-(S)-(+)-4-carboxy-2-ethyl-5-methyl-2-hexenoic acid (13a) and its (R)-(−)-enantiomer (13b) were esterified with chloromethyl methyl ether in the presence of triethylamine to give the corresponding bis(methoxymethyl) esters (26a and 26b). Oxidation of 26a with potassium permanganate and subsequent acidic hydrolysis afforded γ-lactone acids, 6a (2S
4-羧基-4-乙基-3-羟基-2-异丙基-4-丁内酯的所有立体异构体 (4a,b–7a,b) 都已合成,这是 axillaridine 的 necic 酸成分。甲基(E)-(S)-(+)-2-乙基-4-甲氧基羰基-5-甲基-2-己烯酸(12a)被转化为γ-内酯酸、4a(2S、3S、4S)、5a( 2S,3R,4R) 和 5b (2R,3S,4S),通过一系列反应:用间氯过苯甲酸环氧化,在氯化锡 (IV) 存在下用丙酮处理,用甲酸酸性水解,和用氢氧化钡碱水解。类似地,(R)-(-)-对映异构体(12b)也被转化为γ-内酯酸4b(2R、3R、4R)、5b和5a。随后,(E)-(S)-(+)-4-羧基-2-乙基-5-甲基-2-己烯酸(13a)及其(R)-(-)-对映异构体(13b)用氯甲基甲基酯化在三乙胺存在下生成相应的双(甲氧基甲基)酯(26a 和 26b)。用高锰酸钾氧化 26a 并随后进行酸性水解,得到