with p-TSA in methylene chloride-acetone was carried out as in the preparation of 33 from 31. The product crystallized from methanol as needles (37 mg, mp 259-261°) in a yield of 82%:[a]ses 553°; [a]d 131°; Xmax 238 µ (e 15,300); pmax 1755 and 1115 cm-1 (17,21-cyclic carbonate).
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