Phenolic hydroxyl groups, targeted

Preparation of enantiopure intermediates by the use of oxidation reactions was not limited to the synthesis of AB segment (J )-10. The synthesis of the modified daimomycinone, 9-deacetyl-ll-deoxy-9-hydroxymethyldauno-mycinone 44 by Naruta et al. provides an example of enantioselective epox-idation at the stage of a tetracycHc intermediate (Scheme 8) [56]. TetracycUc quinone 42, with the required stereochemistry of the C-4 and C-9 substituents and a protected phenolic hydroxyl group, was prepared in a tandem Michael-Diels-Alder addition of pentadienyltin with acryoylquinone 40 mediated by Lewis acid [57], followed by demethylation, acetylation, and selective hydrolysis. Sharpless enantioselective epoxidation [58] of 42 yielded epoxide 43 in 80% yield and 96% ee. Further transformations of 43 by known procedures, indicated in Scheme 8, furnished the target anthracyclinone 44 in 36% yield from 42. 

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