POLYMERIZATION OF CEPHALOSPORINS IN AQUEOUS SOLUTION

The polymerization of 7 cephalosporins, including ceftizoxime Na (CZXj , cefotaximeNa (CTX) . ceftriaxone Na (CTRX),cefotiam 2 HCI (CTM) . eefamandole Na (CMD) i cefazolin Na(CZL) and cefalotln Na (CLT), in aqueous solution has been investigated in relation to their chemicalstructuree. The aqueous solution of cephalosporins was eluted on DEAE-Sephadex A-25 column by a lineargradient of 0.2～3.0 mol.L^-1 NaCl (pH 7.4～9.4) at ambient temperatute. The ftactions werecharacterized by UV. CD, FAB-MS, and NMR spectrometries. No pelymers were observed from CTM,CTRX, CMD, CZL, and CLT solutions, while CZX and CTX were found to fotm dimers within a fewdays. The dimers were evidently confirmed to form through the intermolecular aminolysis of the β-lactamcarbonyl moiety by the NH₂ group in the second molecule. However, the steric and ionic charge hindranceniay have a direct effect on the polymerization.