PURPOSE: To obtain a compound excellent in gastric inhibitory effect and gastrointestinal mucosa protecting effect on gastric ulcer and duodenal ulcer model and useful as an anti-peptic ulcer agent excellent in safety. ;CONSTITUTION: A compound (salt) of formula I (R1 and R2 are each H or a lower alkyl; R3 and R4 are each a lower alkyl), e.g. 2-[2-(N,N-diethylamino) benzylthio]-5,6,7,8-tetrahydropyrido[3,4-α]pyrimidin-4(3H)one. This compound is obtained, e.g. by reacting a compound of formula II with a compound of formula III in the presence of a base such as sodium hydroxide in a solvent such as methanol at -10°C to the solvent reflux temperature for 10min to 24hr to synthesize a compound of formula IV through an S-benzylation reaction and then reacting a compound of formula R1X (X is Cl, Br, I, methanesulfonyloxy, etc.) therewith in the presence of a base in a solvent such as methanol at -10°C to the solvent reflux temperature for 1 to 48hr.;COPYRIGHT: (C)1995,JPO
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