PREPARATION AND PROPERTIES OF DI-(ETHYLENEGLYCOL), TRI-(ETHYLENEGLYCOL) AND POLY-(ETHYLENEGLYCOL) ESTERS OF 2-BENZOXAZOLON-3-YL-ACETIC ACID

2-Benzoxazolon-3-yl-acetic acid was esterified with diethylene glycol, triethylene glycol and polyethylene glycols with M(W) in the range of 200-1000 D by means of the dicyclohexylcarbodiimide procedure in tetr ahydrofuran, resulting in the corresponding monoesters in comparativel y good yields (70-92%). The products were characterized by H-1-NMR, i. r. and u.v.-spectra as well as by GPC, VPO and DSC methods. The relati vely narrow molecular weight distribution was preserved in the process of the chemical modification. The degree of esterification is gradual ly decreasing from 91% to 44% with the increase of the length of the p olyether chain. The synthesized conjugates are homogeneous as judged b y GPC analysis, but clear evidence for heterogeneity is obtained by th e more sensitive HPLC technique. The molecular mass of the polyethylen e glycols used affects the physicochemical properties thus providing 2 -benzoxazolon-3-yl-acetic acid polyethylene glycol conjugates of varia ble properties able to meet different kind of demands. We found that t he conjugate with PEG400 is extremely useful as a substrate in the pen icillin amidase catalysed transfer of 2-benzoxazolon-3-yl-acetyl moiet y on 7-aminodesacetoxy-cephalosporanic acid offering a new cephem in h igh yield (70%).