Abstract
Under benzilic acid rearrangement conditions and acidic work-up, 6β,19-oxido-2,17-dihydroxyandrosta-1,4-dien-3-one ( 1) underwent unusual, extensive rearrangement affording a furopyranone ( 3) in high yield. This product was the result of B-ring contraction, double bond isomerization and benzilic acid rearrangement of 1, followed by acid catalyzed cyclization of the carboxy intermediate with the vinyl ether portion of the molecule. Alternatively, alkylation of the barium salt ( 2) of the reaction mixture with dimethyl sulfate in dimethyl formamide gave a carbomethoxy dihydrofuran derivative ( 6). Oxidation of the furopyranone ( 3) with Jones reagent produced a furanone derivative ( 5) formed via hydrolysis and oxidative-decarboxylation. The complex molecular structures of these rearrangement products were determined through extensive analysis of NMR spectra utilizing double resonance and Eu(FOD) 3 shift reagent. The structural assignments are supported by a proposed mechanism of formation.
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