Studies on Taxane Synthesis. III. Stereocontrolled Synthesis of a Twelve-Membered Lactam Sulfide as a Precursor of 4,8,11,11-Tetramethyl-3-oxobicyclo(5.3.1)undec-8-ene.
Studies on Taxane Synthesis. III. Stereocontrolled Synthesis of a Twelve-Membered Lactam Sulfide as a Precursor of 4,8,11,11-Tetramethyl-3-oxobicyclo(5.3.1)undec-8-ene.
A general and efficient route to enantioselective synthesis of pumiliotoxin A alkaloids via a common key intermediate
作者:Bing Wang、Kai Fang、Guo-Qiang Lin
DOI:10.1016/j.tetlet.2003.08.113
日期:2003.10
A general and efficient formal synthesis of pumiliotoxins and allopumiliotoxins has been achieved via a common key intermediate 3a. Our route featured a novel one-pot substitution–ring-opening sequence and an efficient Claisen-type condensation. This method is also applicable to quinolizidine derivative 2b.
Studies on Taxane Synthesis. III. Stereocontrolled Synthesis of a Twelve-Membered Lactam Sulfide as a Precursor of 4,8,11,11-Tetramethyl-3-oxobicyclo(5.3.1)undec-8-ene.
作者:Yasuo OHTSUKA、Takeshi OISHI
DOI:10.1248/cpb.39.1359
日期:——
Stereocontrolled synthesis of two twelve-membered lactam sulfides 37 and 38 as precurors of 8, 11, 11-trimethyl-3-oxobicyclo[5.3.1]undec-8-enes constituting the A and B rins of taxane-diterpenes was achieved.The keystep involves a Diels-Alder reaction of maleic anhydride and the E-diene 18 for introduction of the requisite cis arrangement of substitutions at the C-1 and C-7 positions.The resulting adduct was converted exclusively into the lactone 21b in five steps : 1) hydrolysis, 2) iodo-lactonization, 3) BH3 reduction, 4) Zn reduction, 5) methylation.The benzyl group of 26 could be selectively removed by heating with Raney Ni(W-2) in EtOH in nearly quantitative yield without hydrogenation of the double bond.