General Enantiospecific Route to Isochromanquinones. Synthesis of (-)-Nanaomycin D

Article abstract of DOI:10.1021/jo00104a004

A general enantiospecific synthesis of isochromanquinones is presented.This entails an efficient synthesis of (3aS,5S,7aR)-7-bromo-3,3a,5,7a-tetrahydro-5-methyl-2H-furo<3,2-b>pyran-2-one (12) and ultimately the lithium agent 15 from commercially available L-rhamnose.Addition of 15 to the appropriate cyclobutenedione followed by thermolysis of the resulting cyclobutenone leads to the isochromanquinones 16a-c.In an analogous fashion the naturally occurring product, (-)-nanaomycin D, was synthesized.In addition, new methodology involving the ring expansion of iminocyclobutenones to aminophenols was discovered.