Application of molecular modelling to natural products: a biogenetic study of (+)-spathulenol and (+)-allospathulenol

A conformational analysis of (+)-spathulenol and its related stereoisomers was performed using the semiempirical program MNDO. The obtained theoretical results were tested by checking the agreement of a selected calculated property (3J(H-H)) With the experimental value. The theoretical values of the vicinal coupling constants were calculated for all possible stereoisomers of spathulenol, including the ones not yet isolated, to allow their identification as natural and/or synthetic products. A biogenetic study was then undertaken using both the ''saddle'' technique, as implemented in the AMPAC package, and the coordinate reaction method. According to the results obtained, both spathulenol and allospathulenol should originate from two different conformations of a germacradiene precursor with both double bonds in the E configuration.