作者:Michiharu Kato、Yukio Matsumura、Kiyoshi Heima、Akira Yoshikoshi
DOI:10.1246/bcsj.61.1991
日期:1988.6
11-Acetoxy-12bα-methoxymethyl-4,4,6aα,9-tetramethyl-1,2,3,4,4aα,5,6,6a, 12aβ,12b-decahydro-12H-benzo[a]xanthene (34), which has been expected as a promising key intermediate for the synthesis of siccanin (1), was synthesized via acid-catalyzed cyclization of 1α-(2-hydroxy-6-methoxy-4-methylbenzyl)-8aα-methoxymethyl-2,5,5-trimethyl-1,4,4aα,5,6,7,8,8aα-octahydronaphthalene (13) and isomeric exo olefin 21. The phenol acetate 34, however, was so resistant to oxidation that no corresponding 12-oxo derivative, which was expected to provide 11-acetoxy-12bα-acetoxymethyl-12-oxo-4,4,6aα,9-tetramethyl-1,2,3,4,4aα,5,6,6a,12aα,12b-decahydro-12H-benzo[a]xanthene (4) on epimerization at its C(12a) position as well as hydrofuran ring formation at the C(12) position with its angular methoxymethyl substituent, was obtained.
11-乙酰氧基-12bα-甲氧甲基-4,4,6aα,9-四甲基-1,2,3,4,4aα,5,6,6a,12aβ,12b-十氢-12H-苯并[a]黄烷 (34),被预计为合成西卡宁 (1) 的一个有前景的关键中间体,通过 1α-(2-羟基-6-甲氧基-4-甲基苯基)-8aα-甲氧甲基-2,5,5-三甲基-1,4,4aα,5,6,7,8,8aα-八氢萘 (13) 与异构体外烯烃 21 的酸催化环化反应合成。然而,酚醋酸酯 34 对氧化的抗性极强,以至于未获得相应的 12-氧基衍生物,该衍生物预计在其 C(12a) 位点通过表异构化和在 C(12) 位点形成含有角基甲氧基甲基取代基的氢呋喃环,将生成 11-乙酰氧基-12bα-乙酰氧基甲基-12-氧基-4,4,6aα,9-四甲基-1,2,3,4,4aα,5,6,6a,12aα,12b-十氢-12H-苯并[a]黄烷 (4)。