Synthesis and Absolute Configuration of Nocardione A and B, Furano-o-naphthoquinone-Type Metabolites of Nocardia sp. with Antifungal, Cytotoxic, and Enzyme Inhibitory Activities
(±)-Nocardione A (1), (S)-(−)-nocardione A, and (R)-(+)-nocardione B (2) were synthesized by starting from the enantiomers of propylene oxide and 5-benzyloxy (or methoxy)-1-tetralone. The absolute configurations of the naturally occurring (−)-1 and (−)-2 were established as (S).