Abstract
| - Orthoesterol B, a marine natural product exhibiting antiviral activities, contains a [3.2.1]-bicyclic orthobutyrate bridging the steroid side chain and ring D. A biosynthetic reaction was proposed by which rearrangement ofan epoxy ester results in the formation of the orthoestermoiety. Steroidal model compounds incorporating 16-butyroxy and 20,22-epoxy groups were synthesized from tigogenin and were shown to rearrange to orthoesters under mildacidic catalysis.
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