Rubiginones are a family of the natural products that have been isolated from the fermentation broth of Streptomyces griseorubiginosus.Rubiginone A2 1 was claimed to be useful in the treatment of AIDS and Alzheimers disease.The absolute stereochemistry has been determined by the O-methyl mandelate method.Its analogue,benzopyrenomycin(2) has a unique benzo[a]pyrene-type skeleton and shows strong cytotoxic activity against various tumor-cell lines.For instance,benzopyrenomycin exhibited GIs0 of 3.2 μg/mL and 4.2 μg/mL for L-929 and K562 cell lines,respectively.2 The absolute configuration of benzopyrenomycin(2) was reported by Hertweck et al.,which is the same as that of rubiginone A2(1)(2R,3S),based on their similar molecular structures and close OR values(+50°for 1 and+38° for 2 in chloroform),including the evidences that assigning its absolute configuration of 3using Mosher methods,3 in which 3 can be converted into 2.