Platinum Metals Rev., 1961, 5, (4), 131
Synthesis of Penicillin Derivatives
Hydrogenation with Palladium Catalyst
An important advance in medical treatment, made possible by the synthesis of penicillin derivatives of greater antibiotic activity than those produced naturally, has recently been announced by Beecham Research Laboratories Ltd.
The first major step in a long programme of research was the isolation of the common nucleus of the penicillin compounds, 6-amino penicillanic acid, which has the simple basic structure of the penicillins without any side- chain other than one hydrogen atom. From this compound it became possible to produce an immense number of penicillins that could not be obtained from the natural mould by the introduction of substituent groups into the side-chain of existing penicillins, or in other words, into the amino group of 6-amino penicillanic acid. Very broadly, the replacement of one hydrogen in the simple side-chain of the penicillin nucleus by one of a wide range of aminoacyl groups can yield a variety of derivatives, some of which possess activities against a wider range of infections than did earlier preparations. Others of the range are either more readily absorbed orally than the older penicillins or are lethal to certain strains of staphylococci that have hitherto destroyed penicillins by producing a substance called penicillinase.
In the course of preparing these synthetic penicillins, the 6-amino penicillanic acid is coupled with the desired amino-substituted carboxylic acid having its amino group protected, and the protective group is then removed by catalytic hydrogenation. This last procedure must be carried out under conditions sufficiently mild to avoid attack on the penicillin nucleus with subsequent loss of antibiotic activity, and it has been found that, with a palladium catalyst on an inert support such as barium carbonate, this reaction can successfully be carried out at room temperature and atmospheric pressure.