Directed <i>ortho</i> metalation reactions. Convergent synthesis of "angular" anthracyclinones ochromycinone and X-14881 C

Abstract

Convergent syntheses of the benz[a]anthraquinone natural products X-14881 C (2c) and ochromycinone (2d) have been achieved using aromatic directed metalation strategies. Key steps involve (a) the condensations of dilithiated cis-tetralol (13a) with the aldehydo o-anisamide 14 and of methoxymethyl protected aldehyde 17b with lithiated o-anisamide (18) to give, after acid-catalyzed cyclization, the phthalide 16, and (b) the regiospeciflc hydroxyselenylation of anthraquinone 22 to provide the hydroxyselenide 23.