Abstract: The ampicillin derivatives represented by the general formula ##SPC1##Wherein R represents ##SPC2##Wherein R' represents a hydrogen atom, a methyl group, or an ethyl group and A and B each represents a hydrogen atom, a hydroxyl group, a methyl group, a methoxy group, a nitro group, or a halogen atom and further said B may combine with A on the carbon atom at the position to form ##SPC3##Group (where in Z represents --CH=N-- or --CH=CH-- and an R.sup.2 represents a hydrogen atom, a hydroxyl group, a phenyl group, a methyl group, an ethyl group, a methoxy group, an ethoxyl group, a methylthio group, a trifluoromethyl group, a halogen atom, a nitro group, an acetyl group, an acetamido group, a ethoxycarbonyloxy group, or a methylsulfonyl group and further R.sub.2 and ##SPC4##May form a thiazole, isothiazolo, pyrrolo, furo, or benzo fused ring which may be substituted by an oxo group, a methyl group, or an acetyl group) and the dotted line means an arbitrary double bond, ##SPC5##Wherein R.sup.3 and R.sup.

Abstract: The oxofuryl ester derivatives of 6-(.alpha.-amino-phenylacetamido)penicillanic acid, 7-(.alpha.-aminophenylacetamido)-cephalosporanic acid, or 7-(.alpha. -aminophenylacetamide)desacetoxycephalosporanic acid represented by the general formula ##SPC1##Wherein A represents ##SPC2##Wherein R.sup.1 and R.sup.2, which may be the same or different, each represents a hydrogen atom or a lower alkyl group, said R.sup.1 and R.sup.2 may form together a 1,3-butadienylene group, R.sup.3 represents a hydrogen atom or an acetoxy group, andMeans a single bond or a double bond, and acid addition salts of them. When those compounds are orally administered, they are readily absorbed by the intestines and show antibacterial activity by splitting their ester bonds. The rate of absorption of the compounds by the intestines are higher and the toxic property of them is less than those of known compounds similar to the above compounds.