Formation of constrained, fluorescent peptides via tryptophan dimerization and oxidation

A new approach for the construction of highly fluorescent chromophores is described. It involves the initial acid-promoted delta1,delta1' dimerization of tryptophan-containing peptides, followed by oxidation, to produce heterodetic cyclic peptides. The dimerization products are treated with DDQ to induce the dehydrogenation of the indole ring, resulting to the removal of the stereogenic centers. Remaining in the solution is a fully aromatic delta1,delta1'-ditryptophan in high yield.