GB1011650A - L-(-)-ª‡-methyl-ª‰-(3,4-dihydroxy-phenyl)-alanine - Google Patents

Abstract

L - (-) - a - Methyl - b - (3,4 - dihydroxyphenyl) -alanine is prepared by reacting 3,4-dimethoxy-phenyl-acetone, an alkali metal cyanide and an ammonium salt in a concentrated aqueous solution of ammonia, reacting the D,L- a - amino - a - (3,4 - dimethoxy - benzyl) - propionitrile obtained with D-tartaric acid at a temperature of 0 DEG to 20 DEG C. in aqueous suspension, separating off the precipitated bitartrate of D - a - amino - a - (3,4 - dimethoxy - benzyl)-propionitrile, neutralizing the mother liquor and extracting with an inert organic solvent, treating the extract with a hydrohalic acid to form an L - (x) - a - amino - a - (3,4 - dimethoxybenzyl) - propionitrile hydrohalide and hydrolysing this by boiling with an aqueous hydrohalic acid to L - (-) - a - methyl - b - (3,4 - dihydroxyphenyl) - alanine, the bitartrate of D - a - amino - a - (3,4 - dimethoxy - benzyl) - propionitrile obtained by the optical separation being recemized in a neutral or alkaline medium to D,L - a - amino - a - (3,4 - dimethoxy - benzyl)-propionitrile which is then returned to the separation stage. In a modification of the process the 3,4-dimethoxy-phenyl-acetone is used in the form of its bisulphite adduct and the reaction with the alkali metal cyanide is carried out in the concentrated aqueous solution of ammonia without the use of the ammonium salt.