Diastereoselective triple radical cyclization of a bromomethyldimethylsilyl allyl ether

Article abstract of DOI:10.1016/0040-4039(96)01383-4

A convergent strategy to construct the B-ring in an AC → ABC cyclization to the taxane framework was tested. The bicyclic bromomethyldimethylsilyl ether 2 was efficiently synthesized by a sequence proceeding through the alkylation of the C-ring malonate 4 by the hindered A-ring bromide. 3. The desired tandem 5-exo-trig/8-exo-dig cyclization of 2 to diol 1 was not observed. An alternative pathway was indicated by isolation of crystalline tetracyclic diastereomers 12a and 12b, derived by a diastereoselective sequence of three radical cyclizations.