NEW MATERIAL:A heterocyclic carboxylic acid ester derivative shown by formula I [R1 and R2 are H, lower alkyl, lower alkoxy, halogen, nitro, trifluoromethyl or R1 and R2 are neighbored to form group shown by formula II (p is 3-5) or formula III (q is 1 or 2); R3 is lower alkyl or lower alkoxy; R4 and R5 are lower alkyl or (substituted) aralkyl or R4 and R5 are bonded to from ring; Ar is (substituted) phenyl or (substituted) heteroaryl; X is O, S or methylene; m is 1-4; n is 2-4] or acid addition salts thereof.

EXAMPLE: 2-Benzyl-3,4-dihydro-4-(2-dimethylaminoethyl)-3-oxo-2H-1-,4- benzothiazine-2-carboxylic acid methyl ester.

USE: A circulation improver for cerebral and cardiac systems.

PREPARATION: For example, a compound shown by formula IV is reacted with a compound shown by formula V to give a compound shown by formula VI, from which a compound wherein X in the formula I is O is obtained.