Addition of Ester Enolates to <i>N</i>-Alkyl-2-fluoropyridinium Salts: Total Synthesis of (±)-20-Deoxycamptothecin and (+)-Camptothecin
作者:M.-Lluïsa Bennasar、Ester Zulaica、Cecília Juan、Yolanda Alonso、Joan Bosch
DOI:10.1021/jo026173j
日期:2002.10.1
dihydropyridones or 2-pyridones have been prepared by nucleophilic addition of alpha-(methylsulfanyl)ester enolates to N-alkyl-2-fluoropyridinium salts, followed by acid hydrolysis or oxidation with concomitant hydrolysis, of the intermediate 2-fluoro-1,4-dihydropyridine adducts, respectively. Addition of the enolate derived from isopropyl alpha-(methylsulfanyl)butyrate to N-(quinolylmethyl)-2-fluoropyridinium
通过将α-(甲基硫烷基)酯烯酸酯亲核加成到N-烷基-2-氟吡啶鎓盐中,然后酸水解或伴随水解的方式氧化中间体2-氟代,制备了几种4-取代的二氢吡啶酮或2-吡啶酮。 1,4-二氢吡啶加合物。将衍生自异丙基α-(甲基硫烷基)丁酸酯的烯醇盐添加到N-(喹啉基甲基)-2-氟吡啶鎓三氟甲磺酸酯21中,然后进行DDQ处理,得到吡啶酮29,从中已知(+/-)-20-脱氧喜树碱(31)喜树碱的前体是通过自由基环化-脱硫反应合成的,随后通过化学选择性还原精制内酯E环。从手性2-羟基丁酸衍生物的烯醇化物开始的相似序列(33)提供了天然(+)-喜树碱(37)的通道。