A SYNTHETIC APPROACH TO THE QUASSINOIDS
A SYNTHETIC APPROACH TO THE QUASSINOIDS
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DOI：
10.1021/jo00192a004
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发表时间：
1984-01-01
影响因子：
3.6
通讯作者：
UTAWANIT, T
中科院分区：
文献类型：
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作者：
HEATHCOCK, CH;MAHAIM, C;UTAWANIT, T
开发了类苦木素的合成路线。 2-甲基环己酮与1-氯-3-戊酮的两级稠合得到三环二烯酮9 (60%)，其在乙酸中被乙酰铬酸盐氧化得到二烯二酮27 (80%)。该材料的双缩酮化，随后水解共轭烯酮缩酮，得到单缩酮 30 (77%)，以及回收的 27。30 的环 C 通过 Stiles 和 Reich 方法官能化，得到不饱和酮酯 33 (73%)。后一种材料与烯酮缩醛 35 在 5-6 kbar [千气压] 和室温下反应，得到加合物，通过用 KF 水溶液处理进行脱甲硅烷基化；酮二酯 39 的产率为 95%。 39 与 m-CPBA 顺利发生环氧化，得到 46 (88%)，通过两步 Sharpless 程序将其转化为烯丙醇 40 (78%)。最后，氯铬酸吡啶引发 40 的溶剂解环化，以 55% 的产率得到[内酯] 41。在研究过程中，还发现β-酮酯46被m-CPBA氧化成47 [1-1-二甲基乙基(.+-.)-(4''.α.,4''a5*,5''a.β.,6''a.β.,7''.α.,8''.β.,10''a.α.,10''.β.)-十氢-8''-氢xy-8''-(甲氧基羰基)-4'',6a,10''b,三甲基-9''-氧代螺[1,3-二氧戊环-2,3-(4''H)-[2H]-菲-[8a,9-b]环氧烯]-7''-乙酸酯]在定量产量上。
A synthetic route to the quassinoids was developed. Two-stage annelation of 2-methylcyclohexaone with 1-chloro-3-pentanone gives tricyclic dienone 9 (60%), which is oxidized by acetyl chromate in acetic acid to give dienedione 27 (80%). Bisketalization of this material followed by hydrolysis of the conjugated enone ketals provides monoketal 30 (77%), along with recovered 27. Ring C of 30 is functionalized by the Stiles and Reich methods to obtain the unsaturated keto ester 33 (73%). The latter material reacts with ketene acetal 35 at 5-6 kbar [kilobarometer] and room temperature to give an adduct that is desilylated by treatment with aqueous KF; keto diester 39 is produced in 95% yield. Epoxidation of 39 occurs smoothly with m-CPBA to give 46 (88%), which is converted into allylic alcohol 40 by the 2-step Sharpless procedure (78%). Finally, pyridinium chlorochromate induces solvolytic cyclization of 40, affording [lactone] 41 in 55% yield. In the course of the investigation, it was also discovered that .beta.-keto ester 46 is oxidized by m-CPBA to 47 [1-l-dimethylethyl(.+-.)-(4''.alpha.,4''a5*,5''a.beta.,6''a.beta.,7''.alpha.,8''.beta.,10''a.alpha.,10b.beta.)-decahydro-8''-hydroxy-8''-(methoxycarbonyl)-4'',6a,10''b,trimethyl-9''-oxospiro[1,3-dioxolane-2,3-(4''H)-[2H]-phenanthro-[8a,9-b]oxirene]-7''-acetate] in quantitative yield.