Abstract
(R)-6-Hydroxy-7-isopropyl-3-(3-methoxypropyl)-3, 4-dimethylnaphtho[2, 3-b]furan-2(3H)-one (3), prepared from (+)-dehydroabietic acid (2), was converted into (R)-9-acetoxy-6-benzoyloxy-7-isopropyl-3-(3-methoxypropyl)-3, 4-dimethylnaphtho[2, 3-b]furan-2, 5, 8(3H)-trione (10) and its 9-acetyl compound (11) by a series of reactions : sodium borohydride reduction, acetylation, alkaline hydrolysis, benzoyl peroxide oxidation, Jones oxidation, and m-chloroperbenzoic acid oxidation. The trione 10 was further transformed into (R)-5, 6, 8, 9-tetraacetoxy-7-isopropyl-3-(3-methoxypropyl)-3, 4-dimethylnaphtho[2, 3-b]furan-2(3H)-one (15) by alkaline hydrolysis and reductive acetylation. Since the conversion of 15 into coleon A (1) has already been reported, the present work can be regarded as a new formal synthesis of coleon A.
