The present study was undertaken to evaluate whether a novel series of 2, 6-diaza-5- oxobicyclo [5.4. 0] undeca-1 (7), 8, 10-triene derivatives exhibited antagonistic activity for vasopressin V 1 and V 2 receptors. Most of these compounds were synthesized and showed a high affinity potential for V 2 receptor and low to moderate affinity potential for V 1 receptor. The most potent and V 2-selective compound, N-[4-[2, 6-diaza-6-[2-(4-methylpiper-azinyl)- ...