CYCLIC TAUTOMERS OF TRYPTOPHANS AND TRYPTAMINES-4; SYNTHESIS OF CYCLIC TAUTOMERS OF TRYPTOPHANS AND TRYPTAMINES

Article abstract of DOI:10.1016/S0040-4020(01)92088-5

N_b-Methoxycarbonyltryptophan methyl ester (DL- and L-13) was cyclized to the corresponding trans cyclic tautomer (14) in excellent yield in various acids such as 85percent phosphoric acid or trifluoroacetic acid.The cis cyclic tautomer (15) was formed as the less stable and kinetically controlled product and converted to the more stable trans isomer (14) under the reaction condition.The trans isomer (14) was reverted to 13 on treatment with 10percent sulfuric acid in methanol.Other tryptophan and tryptamine derivatives (6 and 19a) also cyclized to the corresponding cyclic tautomers in similar acidic media.