086ChemInform Abstract The title reaction is shown in detail for the diesters (III) and (IV) which yield the lactones (V) (space group P21/n; Z=4) and (VI), respectively. Cleavage of these compounds according to B) gives the decalones (VII) or (VIII) with complete control over the relative configuration of four contiguous asym. centers. Analogous reactions of the esters (IX), (XI) and (XIII) afford the cyclic systems (X), (XII) and (XIV). Epoxidation of (V) or (VI) yields the products (XV). Treatment of (XVb) with ethanolic potassium carbonate gives the cis-hydroxy ketone ester which undergoes subsequent cyclization to the lactone (XVI). The synthesis of (XVI) whose structure is elucidated by X-ray analysis (space group P21/n; Z=4) represents an example of the stereocontrolled preparation of polysubstituted cis-fused ring systems from the bridgehead enol lactones.
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