Construction of AB-Ring System of Taxane Framework by A-Ring Annulation Strategy: Synthesis of 1-Hydroxy-8,11,11-trimethylbicyclo[5.3.1]undec-7-en-9-one by Way of Intramolecular Aldol Cyclization to Form the C1-C10 Bond.

Construction of the AB-ring system of the taxane framework via an A-ring annulation strategy was demonstrated by base-mediated intramolecular aldol reaction of (Z)-2,2-dimethyl-3-(1-methyl-2-oxopropylidene)cyclooctanone, affording the title compound, 1-hydroxy-8,11,11-trimethylbicyclo[5.3.1]undec-7-en-9-one. A cyclization precursor, the tetra-substituted (Z)-alkene, was prepared from the corresponding cyclooctanone derivative, 3-[(alpha,alpha- dimethylbenzyl)dimethylsiloxy]-2,2-dimethylcyclooctanone via a bicyclic alpha,beta-unsaturated lactone intermediate.