Spirolactones of tyrosine: synthesis and reaction with nucleophiles

Abstract

Several quinonoidal spirolactones (1-oxaspiro[4,5]deca-6,9-diene-2,8-diones) 12 have been synthesized chemically or electrochemically by oxidation of the corresponding tyrosine phenols 3. The spirolactones are of considerable value in peptide chemistry, because they react as active esters with amino acid esters to give dipeptides. In the latter, the side chain of the tyrosine moiety is present as a quinol (4-hydroxycyclohexa-2,5-dien-1-one) system, which can be reduced to the genuine tyrosyl dipeptide. Unsubstituted spirolactones also react as active esters but give dipeptides only in modest yields.