Crystal and molecular structure of alnuserol, a new 11-hydroxylated C31 dammarane-type triterpene from Alnus serrulatoides

Abstract

The molecular structure and absolute configuration of alnuserol, (1), a novel 11-hydroxylated C₃₁ dammarane-type triterpene from Alnus serrulatoides Call., were determined to be (11R,20S,24R)-20,24-epoxy-11-hydroxy-24-methyldammaran-3-one (1) by a combination of spectroscopic and X-ray crystallographic methods. Crystals are orthorhombic, space group P2₁2₁2₁, a= 6.599(2), b= 14.921(3), c= 28.443(8)Å, Z= 4. The structure was determined from diffractometer data by direct methods and refined by full-matrix least-squares techniques to R 0.054 for 2 064 reflections.