Stereochemical Study of a 13β,28-Epoxyoleanane

Abstract

The stereochemistry of 3β-acetoxy-12α-bromo-13β,28-epoxyoleanan-16α-ol (2b) has been examined by n.m.r. methods and established by an X-ray crystallographic examination. Steric hindrance of the 16α-hydroxy group is shown not to be as great as previously reported. The bromo epoxide (2b), C₃₂H₅₁BrO₄, M 579·66, crystallized in the orthorhombic space group P 2₁2₁2₁ with a 16·118(2), b 16·615(3), c 11·024(7) Å, V 2952(1) ų , D_c(Z = 4) 1·304 g cm^-3 , N = N(unique) = 1954, N_o 1731 [I > 2·5σ(I)], N_var = 335, conventional R 0· 039, R_w 0·038.