7-Amino-3-ano-3-cefoxi-4-carboxylic acid (7-Anca) can be used to produce several cephalosporin products, such as cefodobenzyl, cefobutene, cefobotan and cefazoxime, which are very popular in the international and domestic market. This product is a kind of cefalkanic acid with no substituent at 3 positions. 3-OHCBG is obtained by multi-step reaction of penicillic acid G, and then hydroxyl is replaced by chemical reaction.