Concise synthesis of a lactonamycin model system by diastereoselective dihydroxylation of a highly functionalized naphthoquinone

[GRAPHICS] In this Letter, we describe an approach to the highly functionalized tetracycle 6, a model compound corresponding to the CDEF ring system contained in the recently discovered antibiotic lactonamycin. Our approach features an unprecedented, highly stereoselective dihydroxylation of quinone 13a, which leads directly to spirocyclic lactone 15, following acid-promoted deprotection/cyclization. The methodology described herein paves the way for a concise, highly diastereo- and enantioselective synthesis of the natural product.