Radical cyclization strategies to terpenoids; syntheses of (±)-β-cuparenone, (±)-laurene and epilaurenes

Abstract

Radical cyclization of the bromide 8 , obtained in 5 steps from the ketone 9 , furnished exclusively 14 via 6-endo trig cyclization with out any observable amount of 5-exo trig product 1 . 5-Exo dig radical cyclizatlon of the bromo acetate 23 , prepared from 18 via the aldehyde 21 , followed by routine transformations furnished the cyclopentenone 26 , an immediate precursor to β-cuparenone ( 2 ). Similarly, total synthesis of laurenes 4 and 5 was achieved via the 5-exo dig radical cyclization of the xanthate 28 , obtained from the aldehyde 21 .