Publication

Abstract : Regiospecific syntheses of tritium labelled precocene I (5a) and precocene II (5b), the antijuvenile hormones, have been accomplished. The syntheses involved condensations between 2-hydroxyacetophenones (1) with acetone-T to give cross condensation products 2 which on cyclodehydration furnished 2,2-dimethyl-4-chromanones-(2-gem dimethyl-T) (3). Reduction of 3 with lithium aluminium hydride gave chroman-4-ols (2-gem dimethyl-T) (4). Dehydration of 4 furnished 2,2-dimethyl- chromenes- (2-gem dimethyl-T) (5). Starting with appropriate acetophenones and acetone-T, precocene I (7-methoxy-2,2-dimethylchromene) and precocene II (6, 7-dimethoxy-2, 2-dimethylchromene) labelled with tritium in the 2-gemdimethyl positions, have been synthesised in high chemical as well as radiochemical yields.