The structure of laurenene, a new diterpene from the essential oil of Dacrydium cupressinum. Part 2. Crystal structure

Abstract

The structure and absolute configuration of Laurenene (1), a compound possessing a new diterpene skeleton, have been determined by X-ray analysis of the bromo-derivative (2). Crystals are monoclinic, space group P₂₁, with a= 7.318(1), b= 13.824(3), c= 9.731 (1)Å, β= 115.493(5)°, and Z= 2. The structure was solved by the heavy-atom method and the atomic parameters refined by block-diagonal least-squares calculations to R 0.043 over 1 208 independent reflections having F² 2σ(F²) from diffractometer measurements. The absolute configurathon was established by the anomalous dispersion effect. The cycloheptane ring adopts a twist chair conformation and the double bond suffers from substantial steric crowding.