Penicillin Synthesis

After nine years of dogged work, Chemist John C. Sheehan of M.I.T. announced last week that he had discovered a practical method of synthesizing penicillin V, one of the two most useful forms of the natural antibiotic made by the penicillin mold.

Dr. Sheehan had solved one of modern chemistry's most baffling problems. During World War II a thousand chemists working in 39 laboratories in the U.S. and Britain spent an estimated $20 million trying to accomplish it. One researcher succeeded, but he could not figure out how he had done it and could never do it again. Another group produced a minute quantity, but by methods too complicated for practical production.

The molecule is not unusually complicated, but extremely fragile. Any kind of rough treatment, such as heat or acids, makes it fall into fragments that cannot kill any kind of germ. To use the customary chemical methods on penicillin, says Dr. Sheehan, "would be like attempting to repair a fine watch with a blacksmith's sledge and anvil." The critical problem was to find a way to bond a carbon atom and a nitrogen atom to form a chemical ring in the heart of the molecule. Avoiding many standard reagents as too violent, and keeping his solutions at room temperature or lower, Dr. Sheehan finally found a reagent that would do the job.

There is little chance that Sheehan's method will be used to manufacture penicillin V commercially, since it can be made cheaply by fermentation. But now that the delicate molecule can be built up and modified in the laboratory, new kinds of penicillin can be produced. Using Sheehan's methods, Merck, Sharp & Dohme Research Laboratories at Rahway, NJ. has already synthesized ten new penicillin compounds that cannot be made by fermentation. Dr. Sheehan's great hope is that the new synthetic penicillins may prove free of natural penicillin's tendency to cause serious allergic effects in some patients. Best of all, they may cope with those sophisticated germs that have developed complete resistance to natural penicillin and even (in some cases) thrive on it.

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