SYNTHESIS OF THE MONOMERIC UNIT OF GAMMA-ACTINORHODIN

The first syntheses of the monomeric units of actinorhodin 19 and 5-ep i-gamma-actinorhodin 18 are described. The key steps involve addition of 2-trimethylsilyloxyfuran 14 to the 2-acetylnaphthoquinone 13 afford ing the adduct 15 which undergoes oxidative rearrangement to a pyranon aphthoquinone system 16 upon treatment with eerie ammonium nitrate. Na phthoquinone 13 is prepared from naphthol 11 which, in turn, is prepar ed via addition of furan 5 to 1,4-dimethoxy-2,3-dehydrobenzene followe d by treatment with acid.