Crystal and molecular structure of BN 52021, a PAF-acether antagonist. Comparison with the conformation of Kadsurenone and related compounds.

BN52021 (Ginkgolide B) monohydrate C20H24O10 X H2O crystallizes in the triclinic space group P1 with two independant molecules in the unit cell of which parameters are a = 7.627(2), b = 11.514(3), c = 12.941(3)A, alpha = 97.05(2), beta = 90.27(2) and gamma = 108.71(2)o, V = 1067.06A3. Calculated density Dx = 1.320g X cm-3. The crystal structure was solved by Patterson methods starting from dreiding model data. The final reliability index R = 0.099 for 3848 observed reflections collected with a four-circle diffractometer. Anti-PAF activities of Kadsurenone, Kadsurin-A, Kadsurin-B and Piperenone, molecular structure of MIRANDIN-A, related compounds and BN52021 suggest that a distance 0-0 of about 6.6A observed in Kadsurenone and in BN52021 could be favourable to anti-PAF activity.