Absolute configuration of anti-HIV-1 agent (-)-concentricolide: total synthesis of (+)-(R)-concentricolide.

The first enantioselective total synthesis of (+)-(R)-concentricolide, the enantiomer of an anti-HIV-1 agent isolated from Daldinia concentrica, from 2-iodophenol in 7 steps reveals the (S)-configuration for the natural form of the furanophthalide. The key features include an anionic ortho-Fries rearrangement to furnish 3-iodosalicylamide, facile construction of the benzofuran system employing the tandem Sonogashira coupling annulation reaction, directed ortho metalation to introduce a propanoyl group, as well as CBS reduction, establishing the stereocenter enantioselectively.