Peracid induced oxidative rearrangements of triterpenoids: Products of new skeleton from bauerenyl acetate

Treatment of bauerenyl acetate (2) with m-chloroperbenzoic acid at 4 degrees C yielded the migrated products. viz. 7 alpha-hydroxy-14,27-cycloisoursan-3 beta-yl acetate (9) and its 15 alpha-hydroxy derivative (12) belonging to a new skeleton, 7 alpha-hydroxyisours-14-en-3 beta-yl acetate (10) and 14 alpha,15 alpha-epoxy-7 alpha-hydroxyisoursan-3 beta-yl acetate (11), besides 7 alpha,8 alpha-epoxybaueran-3 beta-yl acetate (3), bauera-7,9(11)-dien-3 beta-yl acetate (4), bauera-6,8-dien-3 beta-yl acetate (5), 7 alpha,8 alpha-epoxybauer-9(11)-en-3 beta-yl acetate (6), 7 alpha,8 alpha 9 alpha,11 alpha-diepoxybaueran-3 beta-yl acetate (7) and 8 alpha 9 alpha-epoxy-7 alpha-hydroxybaueran-3 beta-yl acetate (8). The structures of all the products were elucidated mainly on the basis of 2D NMR spectral analyses. The H-1 and C-13 chemical shifts of bauerenyl acetate (2) and its reaction products (3-12) were assigned unambiguously. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.