Synthesis of abnormal peptides: cyclization of Nα-formyltryptophyl residue to 3,4-dihydro-β-carboline-3-carboxylic acid residue in acidic media

Abstract

The intramolecular reaction of Nα-formyltryptophan to 3,4-dihydro-β-carboline-3-carboxylic acid is realized with high yield either in trifluoroacetic acid or in formic acid – concentrated hydrochloric acid solutions. Optically active products are obtained when formylated L- or D-tryptophan are used as starting compounds. The experimental conditions employed are highly specific and the cyclization of Nα-formyltryptophyl residue is realized also in peptides without secondary lytic reactions. The general behavior of Nα-formyltryptophan in formic acid solutions is discussed.