CONFORMATION AND DRUG ACTIVITY OF PENTACYCLO-UNDECANES

The structures of four derivatives of acyclo[5.4.0.0(2,6).0(2.6).0(3,1 0).0(5.9)]undecane have been determined by single-crystal X-ray diffra ction to allow conformational analysis for comparison with pharmacolog ical activity. The compounds are the 8,11-dihydroxy 1, 11-dimethoxy-8- oxo 2, 8-ethylamino-8,11-epoxy 3 and 8-cyano-11-hydroxy-N-octy-18,11-e pimino 4 derivatives. Derivative 4 has the highest calcium antagonist activity in the series. Calculated strain energies were found to paral lel the observed activity trend. However, the more important feature i s a favourable conformational relationship between nitrogen and oxygen functional groups and the hydrophobic C8H17 chain, all kept in a fixe d orientation by the rigid pentacyclo-undecane cage structure.