Crystal structure of cordialin a acetate, an unusual dammarane triterpene hemiacetal

Abstract

The structure of cordialin A has unambiguously been determined to be (24S)-24,25-epoxy-11α-hydroxydammar-20(22)en-23-one 3,19-hemiacetal by an X-ray analysis of its C(11) acetate. Crystals are orthorhombic, space group P2₁2₁2₁, a= 6.431(4), b= 20.530(5), c= 21.777(8)Å, Z = 4. The ring conformations adopted are: for A, a very distorted boat; for B, a flattened chair; for C, a puckered chair; and for D, a distorted envelope