Lichens and fungi. Part 16. The crystal and molecular structures of stictane-3β,22α-diol and 22α-hydroxy-3,4-secostictan-3-oic acid

Abstract

The crystal and molecular structures of the title compounds have been determined from X-ray diffractometer data by direct methods. Crystals of stictane-3β,22α-diol (1) are monoclinic, space group C2 with a= 24.14(1), b= 7.606(3), c= 15.900(7)Å, β= 117.3(1)°, and Z= 4. The structure was refined by full-matrix least-squares to R 0.057 for 1 973 observed reflections. The structure confirmed the boat conformation proposed for the B ring of the triterpane. Crystals of 22α-hydroxy-3,4-secostictan-3-oic acid (3b) are monoclinic, space group P2₁ with a= 8.938(2), b= 27.789(7), c= 6.687(2)Å, β= 111.36(2)°, and Z= 2. The structure was refined by fullmatrix least-squares to R 0.087 for 887 observed reflections. The B ring is shown to have a slightly flattened chair conformation and to possess one equatorial and three axial substituent groups.