| 摘要 |
N-Terminal beta , gamma -didehydrovaline di- and tri-peptides are reacted with isopenicillin N synthetase to form 3-exomethylenecepham-4-carboxylic acids, e.g., delta -(L- alpha -aminoadipoyl)-L-cysteinyl-D- beta , gamma -didehydrovaline is incubated with the purified enzyme to provide 7 beta -(L- alpha -aminoadipoylamino)-3-exomethylenecepham-4-carboxylic acid. The 3-exocepham products are useful intermediates to 3-alkoxy-3-cephem and the 3-halo-3-cephem antibiotics.
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