Studies on a novel, potent and orally effective cholecystokinin A antagonist, FK-480. Synthesis and structure-activity relationships of FK-480 and related compounds

We prepared various novel tricyclic 1,4-benzodiazepine derivatives as cholecystokinin (CCK) A antagonists, which were evaluated preliminarily for inhibition of 125I-CCK-8 binding to rat pancreatic membranes in vitro and inhibiting effect on CCK-8-induced inhibition of charcoal meal gastric emptying in mice. On the basis of structure-activity relationship (SAR) studies, as well as the stability and availability of the starting Materials of those compounds, (S)-N-[1-(2-fluorophenyl)-3,4,6,7-tetrahydro-4-oxo- pyrrolo[3,2,1-jk][1,4]benzodiazepin-3-yl]- 1H-indole-2-carboxamide (9f, FK-480) was selected as a candidate compound for further evaluation. The absolute configuration of the precursor of FK-480, (3S)-amino-1,4-benzodiazepine derivative ((S)-8a, R1 = F) was determined by an X-ray crystallographic study of its ureido derivative with (S)-alpha-methylbenzyl isocyanate. FK-480 is now undergoing clinical studies for the treatment of chronic pancreatitis.