The mechanism of the ring enlarging reaction,sorts of ring enlarging catalysts and several preparative methods of converting 7 (phenylacetamido) deacetoxycephalosporin acid to 7 ADCA were summarised.

• 总结了扩环反应的反应机理、扩环催化剂的种类及由头孢烷酸转化成7-ADCA的方法。