Fragmentation procedure for preparing 3-amino-azetidinones

A method for the preparation of a 3-amino-2-oxo-azetidine compound of the formula ##STR14## in which R.sup.1 denotes hydrogen or a group of the formula R.sub.a.sup.1 --O--C(.dbd.O)--, in which R.sub.a.sup.1 denotes lower alkyl, oxo-lower alkyl, halogeno-lower alkyl, cyano-lower alkyl, cycloalkyl, phenyl, phenyl substituted by one to five halogen, one or two lower alkoxy, or one or two nitro, benzyl or diphenylmethyl which can be monosubstituted in the aromatic radical by halogen, lower alkoxy or nitro, R.sup.2 denotes hydrogen, 1-carboxy-lower alkyl, 1-carboxy-1-phenylmethyl, in which the phenyl ring is unsubstituted or monosubstituted to trisubstituted by lower alkyl, halogen, nitro, amino, hydroxy, lower alkoxy, acetoxy, and/or carbamoyloxy, 1-carboxy-1-heterocyclylmethyl, in which heterocyclyl is thienyl, furyl, thiadiazolyl monosubstituted by lower alkyl, or benzthiazolyl, 1-amino-lower alkyl, in which lower alkyl contains one to four C atoms, 1-hydroxy-lower alkyl, in which lower alky contains one to four C atoms and hydroxyl can be replaced by lower alkoxy, acetoxy or carbamoyloxy, 1-carboxy-lower alkenyl, in which lower alkenyl contains two or four C atoms and can be substituted by phenyl or phenylthio, in which groups R.sup.2 the carboxyl group can be replaced by lower alkoxycarbonyl, pivaloyloxymethoxycarbonyl, halogeno-lower alkoxycarbonyl, benzyloxycarbonyl, 4-methoxybenzyloxycarbonyl, 4-nitrobenzyloxycarbonyl, diphenylmethoxycarbonyl, 4,4'-dimethoxydiphenyl-methoxycarbonyl, cycloalkyloxycarbonyl, phenoxycarbonyl, 2- or 4- nitrophenoxycarbonyl, 4-methoxyphenyloxycarbonyl, halogenophenoxycarbonyl, aminocarbonyl, anilinocarbonyl, hydrazinocarbonyl or azidocarbonyl, and in which groups R.sup.2 amino can be substituted by one or two lower alkyl, one acetyl, a group R.sub.1.sup.a --O--C(.dbd.O)--, 2-halogenoacetyl, benzyl, 4-methoxybenzyl, 2- or 4-nitrobenzyl, diphenylmethyl or phthaloyl, and in which groups R.sup.2 hydroxyl can be substituted by lower alkyl, acetyl, carbamoyl, a group R.sub.1.sup.a --O--C(.dbd.O)--, 2-halogenoacetyl, benzyl, 4-methoxybenzyl, 2- or 4-nitrobenzyl or diphenylmethyl, and R.sup.3 denotes hydrogen, hydroxymethyl, wherein hydroxy can be protected by a group R.sub.1.sup.a --O--C(.dbd.O)--, 2-halogenoacetyl, benzyl, 4-methoxybenzyl, 2- or 4-nitrobenzyl or diphenylmethyl, phenyl or 2-phenylvinyl, and a conventional salt of such compound containing a salt-forming group, and/or of a nitrile of the formula R.degree.--CN, in which R.degree. denotes .omega.-carboxyl-.omega.-amino-propoxyphenyl, wherein the .omega.-amino group can be protected by a group of the formula R.sub.1.sup.a --O--C(.dbd.O)-- and carboxyl can be protected in esterified form by lower alkyl, lower alkanoyloxymethyl, 2,2,2-trichloroethyl, benzyl, 4-methoxybenzyl, 2- or 4-nitrophenyl or diphenylmethyl, and a conventional salt of such compound containing a salt-forming group, which comprises treating a 3-(2-hydroxyimino-acetylamino)-2-oxoazetidine compound of the formula ##STR15## in which R.sub.2 and R.sub.3 are as defined above and R.degree. denotes phenyl, hydroxyphenyl, lower alkoxyphenyl, lower alkenyloxyphenyl, aralkyloxyphenyl, lower alkoxycarbonyl-lower alkoxyphenyl, carboxy-lower alkoxyphenyl, .omega.-carboxy-.omega.-hydroxy-lower alkoxyphenyl, .omega.-carboxy or .omega.-lower alkoxycarbonyl-lower alkoxyphenyl, .omega.-amino-lower alkoxyphenyl, .omega.-carboxy-.omega.-amino-lower alkoxyphenyl, furyl, thienyl, thiazolyl, which heterocyclic radicals can be monosubstituted by hydroxy, halogen or amino, in which groups R.degree. hydroxy and amino groups can be protected by a group R.sub.1.sup.a --O--C(.dbd.O)--, and carboxy can be protected in esterified form by lower alkyl, lower alkanoyloxymethyl, 2,2,2-trichloroethyl, benzyl, 4-methoxybenzyl, 2- or 4-nitrobenzyl or diphenylmethyl, or a conventional salt of such a compound containing a salt forming group, in an aqueous medium in the presence of a base, with a compound which is an anhydride or a mixed anhydride with a hydrogen halide of a carbonic acid half-ester of the formula R.sub.1.sup.a --O--C(.dbd.O)--OH, in which R.sub.1.sup.a is as defined above, isolating a compound of the formula I, wherein R.sup.1 is a group of the formula R.sub.a.sup.1 --O--C(.dbd.O)--, and/or isolating a nitrile R.degree.--CN, in which R.degree. denotes .omega.-carboxyl-.omega.-aminopropoxyphenyl, wherein the .omega.-amino group can be protected by a group of the formula R.sub.1.sup.a --O--C(.dbd.O)-- and carboxyl can be protected in esterified form by lower alkyl, lower alkanoyloxymethyl, 2,2,2-trichloroethyl, benzyl, 4-methoxybenzyl, 2- or 4-nitrophenyl, or diphenylmethyl and, if desired in a resulting compound liberating the protected hydroxy, amino and/or carboxy groups present by detaching the protective groups, or protecting in a conventional form free hydroxy, amino and/or carboxy groups present, and, when required, converting a resulting compound containing a salt-forming group to a conventional salt or converting a resulting salt to a free compound.