New alpha-halo:acyl-alpha-L-aspartyl-L-phenylalanine alkyl ester(s) - and use in prepn. of aspartyl-phenylalanine ester(s) esp. aspartame

摘要

Alpha-haloacyl-alpha -L-aspertyl-L-phenylalanine alkyl esters of formula (I) are new; where R = 1-5C alkyl, esp., Me; R' = H or 1-4C opt. branched alkyl; and Hal = Cl, Br or I. New prepn. of alpha-L-aspartyl -L-phenylalanine alkyl esters of formula (II) comprises reacting (I) with thiourea, cyanic acid salts, thiocyanic acid salts, dithiocarbamic acid salts, guanidine, 1,2-ethanedi-thiol, cysteamine, ethanolamine, ethylenediamine, 1,2-diaminobenzene 1,2-dimercaptobenzene, pyrocatechol or o-aminophenol. Process is pref. in a protic solvent, esp. lower alcohol and/or water, pref. at pH 0-8 and pref. at 20-80 deg.C.