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Enzymatic synthesis of beta-lactam antibiotics via direct condensation

Ulijn, R.V. and De Martin, L. and Halling, P.J. and Moore, B.D. and Janssen, A.E.M. (2002) Enzymatic synthesis of beta-lactam antibiotics via direct condensation. Journal of Biotechnology, 99 (3). pp. 215-222. ISSN 0168-1656

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Abstract

In this paper, the feasibility of precipitation driven synthesis of acidic and zwitterionic beta-lactam antibiotics is studied. As an example of the first type, penicillin G was produced in good yield (160 mmol kg(-1)) directly from the free acid and an-tine aqueous substrate suspension, where the synthesis product precipitated. Such a precipitation driven synthesis via direct reversal of the hydrolytic reaction is thermodynamically unfavourable for zwitterionic beta-lactam antibiotics, such as amoxicillin. In this paper, a novel method is suggested to help favour precipitation of (poorly soluble) product salts by deliberate addition of certain counter-ions. After screening a number of different counter-ions, it was found that the amoxicillin anion forms a poorly soluble salt with Zn2+. Despite increased beta-lactam degradation due to the presence of zinc ions, in a synthetic reaction with 0.1 M ZnSO4 present the synthetic yield could be increased at least 30-fold.