title: Preparations ofN, N'-ethylene-bridged dipeptides(eXX) constructed from (S)-methionine, -tryptophan, -tyrosine and-N(ɛ)-benzyloxycarbonyllysine through acid-catalyzed cyclization.
abstract: N, N'-Ethylene-bridged bis-(S)-methionine[(2S, 7S)-2, 7-bis(2-methyl-thioethyl)-3,6-diazaoctanedioic acid] derived from (S)-methionine and 1,2-dibromoethane was cyclized and esterified simultaneously in boiling ethanol in the presence of an appropriate amount of strong acid such asp-toluenesulfonic acid, affording a cyclic compound,N, N'-ethylene-bridged (S)-methionyl-(S)-methionine ethyl ester {ethyl(2S, 3'S)-4-(methylthio)-2-[2'-oxo-3'-(2-methylthioethyl)-1'-piperazinyl] butanoate}, exclusively in 80-90% yields. It was also found that, by applying this method, 70-80% yields of the otherN, N'-ethylenebridged dipeptides containing (S)-tryptophan, -tyrosine and -N(ɛ)-benzyloxycarbonyllysine were obtained.
authors.affiliation: Department of Chemistry, Faculty of Science, Osaka City University, Sumiyoshi-ku, Sugimoto 3-3-138, 558, Osaka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yamashita
authors.forename: H
authors.initials: H
authors.lastname: Takenaka
authors.forename: Y
authors.initials: Y
authors.lastname: Kojima