Rearrangements of Derivatives of Methyl 9,11-Dihydroxy-(-)-Kauran-19-Oate to New Skeletal Diterpenes

The acid-catalyzed rearrangement of the 11α-acetoxy-9α-hydroxy derivative (8) of methyl (-)-kaur-9(11)-en-19-oate (1) afforded compound (2) the C/D ring system of which is analogous to that of antheridiogen, AAN, (3), the antheridium-inoucing factor from Anemia phyllitidis. On the other hand, the rearrangement of the 9α,11α-dihydroxy derivative (9) under identical conditions led to a mixture of compounds (6) and (11). the 9α-hydroxy-11α-methanesulfonyloxy derivative (12) underwent a pinacolic-type rearrangement with potassium t-butoxide in t-butanol to give a ring B-homo derivative (13).