Syntheses of dehydrorotenoid and benzoxanthone units from 2'-hydroxyacetophenone are described which feature a novel migration of spiro-substituted chroman-4-ones during their oxidative ring expansion. Conjugate reduction affords a trans B/C fused rotenoid and the related cis and trans fused tetrahydrobenzoxanthones. (C) 1998 Elsevier Science Ltd. All rights reserved.
Syntheses of dehydrorotenoid and benzoxanthone units from 2'-hydroxyacetophenone are described which feature a novel migration of spiro-substituted chroman-4-ones during their oxidative ring expansion. Conjugate reduction affords a trans B/C fused rotenoid and the related cis and trans fused tetrahydrobenzoxanthones. (C) 1998 Elsevier Science Ltd. All rights reserved.