The Synthesis of (+)-Coleon A

Abstract

Abstract Partial methylation of (R)-6-hydroxy-3-(3-hydroxypropyl)-7-isopropyl-3,4-dimethylnaphtho[2,3-b]furan-2(3H)-one followed by benzylation afforded the 6-benzyloxy-3-(3-methoxypropyl) derivative, which was converted into the 9-acetyl derivative by the series of reactions; sodium borohydride reduction, acetylation, alkaline hydrolysis, and Jones oxidation. This was oxidized with m-chloroperbenzoic acid to give the 9-acetoxy-5,8-quinone derivative, which was further converted into the 5,6,8,9-tetraacetoxy-3-(3-hydroxypropyl) derivative by hydrogenolysis, reductive acetylation, and demethylation. The tetraacetate in pyridine was treated with o-nitrophenyl selenocyanate in the presence of tributylphosphine and the resulting selenide was oxidized with hydrogen peroxide to give the 3-allyl derivative. This was converted into (+)-coleon A lactone by alkaline hydrolysis and subsequent oxidation. Finally, (+)-coleon A lactone was reduced with sodium borohydride to give (+)-coleon A which was also obtained by lithium aluminium hydride reduction of the 3-allyl derivative.