Abstract: An oxazolidine derivative represented by the formula (I) ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 are H, optionally halogenated alkyl, optionally halogenated alkoxy, OH, halo, NO.sub.2, amino optionally having acetyl or alkyl, COOH, alkoxycarbonyl, CN, alkanoyl, 2-oxazolyl, or R.sup.1 and R.sup.2 may be combined with each other to represent --(CH.sub.2).sub.p -- or --O(CH.sub.2).sub.q O-- (p is 3-5, q is 1-3) to form a ring, m and n are each 0 or 1, R.sup.4 and R.sup.5 are H or alkyl, X is C or N, Y is CH.sub.2 OH, CHO or COOR.sup.6 (R.sup.6 is alkyl, benzyl or H), A is alkylene, carbonyl or sulfonyl, B is alkylene, E is alkylene which may be substituted with halo or is alkenylene, Z is O or S, except for a compound wherein n is 0, m is 1 and Y is CH.sub.2 OH, and except for a compound wherein n is 0, Y is COOR.sup.6 (R.sup.

Abstract: Disclosed are a 1-phenylpyrrolidone derivative having optical activity and represented by the formula (I) ##STR1## wherein R represents an optionally substituted optically active .alpha.-phenylethylamino group, a 1-phenylpyrrolidone derivative represented by the formula (I-a) ##STR2## and processes for preparing the 1-phenylpyrrolidone derivatives represented by the formulas (I) and (I-a), respectively.

Abstract: A benzothiadiazine derivative, hydrate thereof and acid addition salt thereof, the derivative being represented by the general formula (I) ##STR1## wherein X is methylene or a nitrogen atom substituted with a lower alkyl, Y and Z are each methylene or carbonyl, A is phenylene or phenylene substituted with methoxycarbonyl, R.sub.4 is lower alkylene or lower alkenylene, R.sub.1 is a hydrogen atom, acetoxyacetyl, cyclohexylmethyl or benzyl wherein the benzene ring may be substituted with lower alkoxyl, halogen atom, nitro, lower alkyl, methylenedioxy or hydroxyl, R.sub.2 is lower alkyl or phenyl, and R.sub.3 is a hydrogen atom, halogen atom or lower alkoxyl with the exception of the case where X, Y and Z are each methylene, A is unsubstituted phenylene, R.sub.4 is lower alkylene and R.sub.1 is a hydrogen atom; and a peptic ulcer treating agent containing as an effective component the above derivative, hydrate thereof or acid addition salt thereof.

Abstract: Disclosed are 2.beta.-substituted-methylpenicillanic acid compounds of the formula ##STR1## wherein n is 0, 1 or 2; and ##STR2## is monocyclic or bicyclic heterocyclic ring group which has 2 to 4 nitrogen atoms as hetero atom in its ring structure and which may be optionally substituted with alkyl, alkoxycarbonyl, phenyl, formyl or benzyloxycarbonyl optionally having alkyl, nitro or a halogen atom on the benzene ring, with the proviso that said heterocyclic ring group is not 1,2,3-triazol-1-yl; or salts or esters thereof.These compounds are useful as .beta.-lactamase inhibitor.