Patent ID: 7038059

Claim:
A process for producing a 4-N-substituted amino-2-aza-1-oxabicyclo[3.3.0]oct-2-ene-6-carboxylic acid ester represented by General Formula (11): wherein R 1 represents an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group which may be substituted or an aralkyl group which may be substituted; R 8 represents an amino-protecting group introduced by an amino-protecting group introducing compound and selected from among an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group which may be substituted, an aralkyl group which may be substituted, an acyl group or an alkoxycarbonyl group; and R 9 represents an alkyl group which may be substituted, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group which may be substituted, an aralkyl group which may be substituted, an acyl group or a carbamoyl group, comprising: the step of adding a Brønsted acid represented by Formula (3): HX (3) wherein X represents a halogen atom, a carboxylic acid residue, a sulfonic acid residue or a phosphoric acid residue, to a mixture of a 2-azabicyclo[2.2.1]hept-5-en-3-one represented by Formula (1): and an alcohol represented by Formula (2): R 1 OH (2) wherein R 1 is defined as above, thereby causing these components to react with each other to form a salt of cis-4-amino-2-cyclopentene-1-carboxylic acid ester represented by Formula (4): wherein R 1 and X are defined as above; the step of allowing the salt of cis-4-amino-2-cyclopentene-1-carboxylic acid ester thus obtained to react with the amino-protecting group introducing compound in the presence of a base to form a cis-4-N-substituted amino-2-cyclopentene-1-carboxylic acid ester represented by Formula (9): wherein R 1 and R 8 are defined as above; and the step of allowing the cis-4-N-substituted amino-2-cyclopentene-1-carboxylic acid ester thus obtained to react with a hypohalogenite and an aldoxime represented by Formula (10): wherein R 9 is defined as above.