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[摘要]：A stereoselective synthesis of a C-1-C-11 building block for the polyol-polyene antibiotic rimocidin has been developed. Its functional groups originate from a disubstituted indane, which underwent Birch reduction, and oxidative cleavage. This provided a dihydropyranone with a beta-keto ester side-chain. The latter was subjected to a Noyori hydrogenation (ds > 97:3). An oxy-Michael addition gave a mixture of two spiroketals. Luche reduction then led to three spiroketals in an 80:10:10 ratio. The major spiroketal became isolable by separating one of the by-products chromatographically and the other by a diastereomer-selective thioketalization. The remaining spiroketal was ring-opened to give a dithiolane. Its CO2Me group was converted into the 1,3-dithiane unit of the target compound (i.e., 47) using an odor-reducing workup procedure, which should prove to be generally useful. |
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