Structure and absolute configuration of vibsanine E isolated from leaves of Viburnum odoratissimum Ker

Abstract

X-Ray analysis has established the structure and absolute configuration of vibsanine E, C₂₅H₃₆O₅, isolated from leaves of Viburnum odoratissimum. It is a ββ-dimethylacrylic acid ester of a novel diterpene. The junction of the two six-membered rings, both of which have the chair conformation, is cis. The seven-membered ring also takes the chair form. Crystals are monoclinic, space group P2₁, with a= 10.907, b= 8.941, c= 12.829 Å, β= 107.63°, Z= 2. The structure was solved by the vector-search method and refined by the least-squares method to R 0.043 for 2 171 independent reflections. The absolute configuration was determined by the Bijvoet method by utilizing the anomalous scattering of light atoms for Cu-K_α radiation.