Total synthesis of (+)-hatomarubigin B

The first total synthesis of (+)-hatomarubigin 3 is described. The tetra-O-acetyl diborate promoted Diels-Alder reaction of 5-hydroxy-8-(2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyloxy)-1,4-naphthoquinone 8 and (E, 1R*,5R*)-3-(2'-methoxyvinyl)cyclohex-2-enol (+/-)-7 gave a mixture of four cycloadducts from which (1S,3S,6S,6aR,12aR,12bS)-1,8-dihydroxy-6-dimethoxy-1-hydroxy-3-methyl-11-(2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyloxy)-1,2,3,4,6,6a,12a,12b-octahydrobenz[a]anthracene-7,12-dione 12 was isolated in 51% yield. Selective methylation and acetylation of 12 gave (1S,3S,6S,6aR,12aR,12bS)-1-acetoxy-6,8-dimethoxy-3-methyl-11-(2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyloxy)-1,2,3,4,6,6a,12a,12b-octahydrobenz[a]anthracene-7,12-dione 10a. Sequential aromatization, photooxidation and hydrolysis of the glucosyl unit gave (+)-3 (98% ee) in an 8% overall yield from 8.