Total Synthesis of (.+-.)-Porosin, a Neolignan from Ocotea porosa and Urbanodendron verrucosum (Lauraceae).
作者:Takashi MATSUMOTO、Yoshio TAKEDA、Masaki OIWAMOTO、Kazunari FUJII、Masashi KISHIDA、Hiroshi SHIBUTANI、Sachihiko IMAI
DOI:10.1248/cpb.43.2099
日期:——
Veratraldehyde was condensed with methyl 2-chloropropanoate to give a glycidic ester. This was hydrolyzed with aqueous sodium hydroxide and the resulting sodium salt was treated with lead(IV) tetraacetate to give 1-acetoxy-1-(3, 4-dimethoxyphenyl)propan-2-one (13). Condensation of 13 with dimethyl malonate, followed by acidic hydrolysis and sodium borohydride reduction afforded (2R*, 3S*, 4R*)-4-(3, 4-dimethoxyphenyl)-2-methoxycarbonyl-3-methyl-4-butanolide (7a). The γ-lactone 7a was then converted into 5'-demethoxyporosin (10) by means of a series of reactions : Michael reaction with methyl vinyl ketone, elimination of the methoxycarbonyl group, acetalization, allylation, deacetalization, and intramolecular aldol reaction. Introduction of a hydroxyl group at the C-5' position in 10, followed by methylation with diazomethane afforded racemic porosin. The synthetic porosin was further converted into 5-demethoxymegaphone acetate.
藜芦醛与2-氯丙酸甲酯缩合得到缩水甘油酯。将其用氢氧化钠水溶液水解,并将所得钠盐用四乙酸铅(IV)处理,得到1-乙酰氧基-1-(3,4-二甲氧基苯基)丙-2-酮(13)。 13 与丙二酸二甲酯缩合,然后进行酸水解和硼氢化钠还原,得到 (2R*, 3S*, 4R*)-4-(3, 4-二甲氧基苯基)-2-甲氧基羰基-3-甲基-4-丁内酯 (7a )。然后通过一系列反应将γ-内酯7a转化为5'-脱甲氧基孔松素(10):与甲基乙烯基酮的迈克尔反应、消除甲氧基羰基、缩醛化、烯丙基化、脱缩醛化和分子内羟醛反应。在10的C-5'位置引入羟基,然后用重氮甲烷甲基化,得到外消旋孔松蛋白。合成的孔隙素进一步转化为5-去甲氧基扩音器乙酸酯。