The Greek Chemist and the Group That Came Off Clean
In 1932 a young chemist from the Peloponnese helped solve the problem that had stopped Emil Fischer. The protecting group he co-invented shaped peptide chemistry for three decades, and the school he built in Athens carried the work into the age of insulin.
Leonidas Zervas was a Greek organic chemist, born in the Peloponnese in 1902, who in 1932 co-authored with his Berlin and Dresden mentor Max Bergmann a paper describing a general method of peptide synthesis built on a protecting group that could be removed without destroying the chain it protected 14. That sentence compresses a problem that had defeated the field's founder, a decade of patient laboratory work, a political upheaval that ended a partnership, and a return home to a country about to be occupied. It is a story with a scene at its centre: a young man in a German laboratory looking at a flask in which a peptide bond had been made without wrecking what lay around it.
The chemistry is half the story. The other half is what one person did with it afterwards, in a country that had no tradition of research in the area, and how that work ran, through his students, into one of the great syntheses of the 1960s.
From Megalopolis to Dresden
Zervas was born in 1902 in or near the town of Megalopolis in Arcadia, in the interior of the Peloponnese. Biographical summaries describe a student in Athens who then went abroad, as ambitious Greek scientists of his generation routinely did, to a German-language laboratory where organic chemistry was done at the highest level 4. He joined the group of Max Bergmann, a protein chemist who had trained under Emil Fischer in Berlin and who directed the Kaiser Wilhelm Institute for Leather Research in Dresden.
An institute devoted to leather may sound an unlikely home for a revolution in peptide chemistry. It was not. Leather is processed collagen, collagen is a protein, and a laboratory charged with understanding hides had every reason to study how amino acids are linked. Bergmann used the position to assemble a research group that worked on proteins and enzymes under an industrial banner.
Fischer's unsolved problem
Emil Fischer had shown at the start of the century that amino acids could be joined into chains and had coined the word peptide for the result. He also left behind a difficulty that he could not solve. To link two amino acids, the acid end of one must react with the amino end of the other. But each amino acid has both ends, so left alone they join in every possible combination. The remedy is to block the amino end of the first with a temporary cap, form the bond, and then take the cap off to expose the amino end for the next step.
The trouble was the removal. The caps available in Fischer's day came off under conditions harsh enough to break peptide bonds as well, so the chain was cut as it was freed. Chemists could make short peptides, and Fischer made some, but anything systematic was out of reach. A usable protecting group needed two qualities that pulled against each other: it had to hold firmly through the coupling and release gently afterwards.
1932: a group that comes off clean
The answer reported by Bergmann and Zervas was to cap the amino end with a benzyl-based carbonate, introduced as a carbobenzoxy group. Their paper, titled in German as a general procedure for peptide synthesis, appeared in the Berichte der Deutschen Chemischen Gesellschaft in 1932 1. The decisive feature was how it was removed. In the presence of a metal catalyst and hydrogen, the cap is cleaved by a quiet reaction that releases toluene and carbon dioxide, two volatile by-products that leave the flask on their own, while the peptide bonds are untouched.
That is what the title of this piece means by a group that comes off clean. There was no acid strong enough to damage the chain and no residue to purify away. The method gave chemists something they had lacked since Fischer: a reliable cycle of cap, couple, uncap, repeat. It is a technique of the bench, and it did not change what a peptide is; but it changed which peptides could be built.
| Requirement | Earlier caps | Carbobenzoxy (1932) |
|---|---|---|
| Hold through the coupling step | Generally held | Held |
| Release without damaging peptide bonds | Failed: removal cut the chain | Catalytic hydrogenation, bonds intact |
| Leave nothing behind to clean up | Residues remained | Volatile toluene and carbon dioxide |
New York, and the choice to go home
Politics then overtook the laboratory. After 1933 Bergmann, who was of Jewish descent, lost his position in Germany. He emigrated to the United States and took up work at the Rockefeller Institute in New York, and members of his group followed him there at various points. Biographical summaries place Zervas in New York for a period in the mid-1930s before he returned to Greece 4. The precise years differ between accounts, and the dates here are left deliberately loose.
Staying would have been the easier course. The United States offered a funded laboratory and a partner of international standing. Zervas went home instead, to a university system with little tradition of the kind of chemistry he had learned and a country that, within a few years, would be at war and then under occupation. The decision belongs to the category of choices that cannot be reduced to career arithmetic, and the record available for this article does not explain it. What the outcome shows is that he made it and that it had consequences.
The Athens school
In Athens he built a research group from almost nothing, in the circumstances of a wartime and then a poor postwar country. The group worked on the chemistry of amino acids and peptides, and it kept pushing at the same question Bergmann and Zervas had begun with: how to protect and unprotect cleanly. A paper from Zervas and a colleague in 1956 described N-tritylamino acids and a new method of peptide synthesis, using the bulky trityl group as an amino cap that comes off under very mild acid 2.
The significance of the trityl work is not that it replaced carbobenzoxy, which it did not. It is that it showed a school that had its own ideas, publishing in the international journals and adding to the toolkit rather than only using it. A new protecting group changes what can be built, because a chemist with two groups that come off under different conditions can protect two ends at once and release them separately. That principle of orthogonal protection came to dominate the field.
Katsoyannis, Photaki and the insulin connection
Students are the surest measure of a school. Among those who passed through the Athens laboratory was Panayotis Katsoyannis, who later worked in the United States and led a laboratory at the University of Pittsburgh. In the 1960s his group was one of those that synthesised the chains of insulin and combined them, work reported in Science in the middle of the decade 3. Another collaborator of Zervas, Ioanna Photaki, is remembered in the history of Greek peptide chemistry for her own contributions to protecting-group methods.
The insulin syntheses of that decade used protecting-group chemistry in the line of descent from the 1932 paper, and the race to make the hormone, which involved groups in the United States and in China as well, is told on this site in its own piece. The point here is narrower. Without a clean way to cap and release an amino end, a chain as long as an insulin chain could not have been built in the laboratory at all. The Greek link in that chain of ideas is real and traceable, even where the details of who worked with whom at which stage are better read from the primary papers than from a summary.
Honours that came late
Zervas died in 1980 in Athens. Biographical summaries record membership of the Academy of Athens and a series of national and international recognitions 4. The pattern, a researcher abroad and a founder at home, whose reputation was larger among specialists than in the public mind, is a familiar one in the history of science. Nobel committees honoured the people who put protecting groups to work on spectacular targets; the person who devised the first generally useful one is less often named.
Where the synthesis articles take over
The carbobenzoxy group was not the last word. Later generations of chemists moved to other protecting groups and to building peptides on solid supports, where the logic of cap, couple and uncap is carried out by machines. But the cycle itself is the one Bergmann and Zervas made possible, and every modern synthesiser, however sophisticated, still repeats it.
The piece on the chemist who named the peptide bond tells the earlier part of the story, and the pieces on the insulin race and on the longest chain anyone had built take it forward. This one has tried to put a name and a biography at the point where the chemistry turned. The name is Zervas.