Starting from non-peptidic sst1-selective somatostatin receptor antagonists, first compounds with mixed sst1/sst3 affinity were identified by directed structural modifications. Systematic optimization of these initial leads afforded novel, enantiomerically pure, highly potent and sst3-subtype selective somatostatin antagonists based on a (4S, 4aS, 8aR)- decahydroisoquinoline-4-carboxylic acid core moiety. These compounds can efficiently be ...