Patulignans A-C, three structurally unique lignans from the leaves of Melicope patulinervia

(±)-Patulignans A–C (1–3), three unique pairs of lignan enantiomers were isolated from the leaves of Melicope patulinervia. Patulignan A (1) possesses an unprecedented dimethyloxonane moiety in nature, meanwhile patulignans B (2) and C (3) are epimers carrying a novel dimethyl-1,6-dioxaspiro[4.5]decane skeleton. Their structures were established by spectroscopy methods and electronic circular dichroism (ECD) calculations. Compounds 1–3 showed significant inhibitory activity against α-glucosidase.