V. А. Haidukevich, I. V. Rudziankova, L. Popova
Mar 13, 2019
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Journal
Proceedings of the National Academy of Sciences of Belarus, Chemical Series
Abstract
3-Isobutylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione, [cyclo(prolyl-leucyl)], which has a wide range of biological effects, was obtained by thermolysis both the L-prolyl-L-leucine methyl ester and the methyl ester L-leucyl-L-proline, for the synthesis of which the removal of tert-butyloxycarbonyl amino protecting groups in tert-butyloxycarbonylprolyl-leucine methyl ester and tert-butyloxycarbonylleucyl-proline methyl ester under the action of a methanolic solution of hydrogen chloride and the treatment of the resulting of methyl esters hydrochlorides L-prolyl-L-leucine and L-leucyl-L-proline with an equimolar amount of triethylamine were used. The starting tert-butyloxycarbonylleucyl-proline methyl ester was prepared like the previously synthesized tert-butyloxycarbonylprolyl-leucine methyl ester by the carbodiimide method. It was found that the cyclization of the methyl ester of L-leucyl-L-proline into the desired diketopiperazine proceeds at a lower temperature than the cyclization of the methyl ester of L-prolyl-L-leucine.