Process for preparation of 4-n-substituted amino-2-aza-1-oxabicyclo[3.3.0] oct-2-ene-6-carboxylic acid esters and process for preparation of their intermediates

摘要

4-N-substituted amino-2-aza-1-oxabicyclo[3.3.0]oct-2-ene-6-carboxylic acid esters are produced by adding a Brønsted acid to a mixture of a 2-azabicyclo[2.2.1]hept-5-en-3-one and an alcohol, thereby causing these components to react with each other to give a salt of cis-4-amino-2-cyclopentene-1-carboxylic acid ester, then allowing the salt of cis-4-amino-2-cyclopentene-1-carboxylic acid ester thus obtained to react with an amino-protecting group introducing compound in the presence of a base, thereby giving cis-4-N-substituted amino-2-cyclopentene-1-carboxylic acid ester, and then allowing this cis-4-N-substituted amino-2-cyclopentene-1-carboxylic acid ester to react with a hypohalogenite and an aldoxime.