A short and convenient access to a trans-hydrindane unit from the anti-meso-acetylmethyldivinylcyclopentane via a radical pathway

An efficient route for multigram synthesis of a trans-hydrindane unit, involving a selective 6-endo-trig α-carbonyl radical cyclization of the α-xanthyl ketone 10 derivating from the anti-meso-acetylmethyldivinylcyclopentane 9 through a xanthate group transfer, is achieved in good yield. Preparation of an advanced intermediate for the Julia–Kocienski coupling, used in the elaboration of the trienic system of vitamin D (or calciferol) analogs, was materialized by conversion of the xanthate moiety to a 2-benzothiazole sulfonyl group.