Gastrin is a typical gastrointestinal hormone, like CCK, secretin, etc. It is known that gastrin accelerates secretion of gastric acid and pepsin and also accelerates growth of gastric mucous cells and especially histamine secretory cells. While gastric acid secretion is stimulated by histamine, acetylcholine, and gastrin, gastrin is the most powerful of these internal substances. Currently known drugs for controlling gastric acid secretion include muscarinic receptor antagonists such as Pirenzepine, histamine H.sub.2 receptor antagonists such as Cimetidine, and H.sup.+ -K.sup.+ ATPase inhibitors such as Omeprazole. However, it has been reported that these drugs induce hypergastrinemia during maintained administration due to the potent inhibitory activity on gastric acid secretion, and the high gastrin level induces an increase of histamine content in the gastric mucosa. The reports also reveal that discontinuation of administration of these drugs is followed by an increase of acid secretion, called rebound, and a high rate of relapses.
The study of gastrin has recently been progressed, and participation of gastrin in various diseases has been elucidated. As a result, it has been suggested that a selective antagonist to gastrin receptors would be useful for the treatment and prevention of diseases induced by disorders of physiological functions related to gastrin, i.e., diseases of digestive organs, particularly peptic ulcers, gastritis, reflux esophagitis, and Zollinger-Ellison syndrome; prevention of a relapse following treatment with an H.sub.2 receptor antagonist or an H.sup.+ -K.sup.+ ATPase inhibitor; or the treatment and prevention of tumours originating in the gastrointestinal system.
Recently, several gastrin receptor antagonists have been reported. For example, amino acid (glutamic acid) derivatives such as Proglumide and benzodiazepin derivatives such as L-365,260 (Japanese Patent Application Laid-Open No. 238069/88) are known. Proglumide exhibits very weak binding activity to gastrin receptors. L-365,260, while having high binding activity to gastrin receptors, do not exert powerful inhibitory activity on gastric acid secretion when administered in vivo.
On the other hand, CCK is widely distributed through the gastrointestinal system and the central nervous system. It is known that CCK exhibits its activities at the peripheries chiefly via CCK-A receptors accelerating pancreatic secretion, gastrointestinal motility and contractions of the gall bladder, inhibition of gastric emptying, and acceleration of growth of some kinds of tumor cells. It is also known that CCK participates in appetite control, analgesia through opiate, and symptoms of psychotic disorders including anxiety and panic disorder in the central nervous system via CCK-B receptors. Accordingly, drugs having a selective antagonistic action to CCK-B receptors are expected to be useful for the treatment of CCK-related disorders in the appetite control system, enhancement and prolongation of analgesia through opiate or non-opiate, induction of anesthesia or analgesia, and the treatment and prevention of symptoms of psychotic disorders including anxiety and panic disorders.
While amino acid (glutamic acid) derivatives such as Proglumide are reported as a CCK-B receptor antagonist, their binding activity to CCK-B receptors is very weak.
An object of the present invention is to provide a compound which selectively antagonizes to gastrin receptors without causing side effects attributed to the CCK-A receptor antagonism and inhibits gastric acid secretion in vivo and is useful for the treatment and prevention of diseases of digestive organs, such as peptic ulcers, gastritis, reflux esophagitis, and Zollinger-Ellison syndrome, and for the treatment of tumour originating in the gastrointestinal system and which also selectively antagonizes to CCK-B receptors without causing side effects attributed to the CCK-A receptor antagonism and is useful for the treatment of CCK-related disorders in the appetite control system, enhancement and prolongation of analgesia through opiate or non-opiate, induction of anesthesia or analgesia, and the treatment and prevention of symptoms of psychotic disorders including anxiety and panic disorder, and an intermediate useful for the synthesis of the compound.