Non-equivalence of methylenedioxy protons in Cyclolignans

Abstract

The conditions for observation of non-equivalence of CH₃0₂ protons in rings A and C of cyclolignans are discussed. The protons of the CH₂O₂ group when present in ring A at 7,8-position are equivalent when ring B is aromatic and non-equivalent when it is hydroaromatic. When the CH₂O₂ group is; present in ring C at 3',4'-positions non-equivalence is observed if there is a second CH₂O₂ function at 7,8-positions or if there is a C = 0 group attached to C-2 of ring B.