a-Amino Acids, compositions and process for preparing said compounds a-ethynyl- and - a-vinyl- 3,4- disubstituted pheynylalanines and esters thereof, have been prepared by reaction of methyl 3,4-dihydroxybenzoate with diphenyldichloromethane, reduction of the so obtained methyl 3,4-diphenylmethylene- dioxy- benzoate to 3,4-diphenylmethylenedioxybenzyl- alcohol, and transforming this to the benzylchloride. This 3,4-diphenylmethylenedioxybenzylchloride reacts with 1-trimethyl- silyl-N- benzylidene-3-aminoprop-1-yneto form 3-(3,4- diphenylmethylenedioxybenzyl) -1-trimethysilyl N-benzylidene-3- aminoprop-1-yne.
With methyl chloroformate this compound gives 3-carbomethoxy-3- (3,4- diphenylmethylenedioxybenzyl-1-trimethylsilyl -N-benzylidene -3-aminoprop-1-yne.
The benzylidene-group, the trimethylsilyl-group and the diphenyl-methylene- group are removed, which results in the formation of a-ethynyl- 3,4-dihydroxy- phenylalanine.
The a-vinyl- analog is obtained by hydrogenation of an intermediate. The compounds have a pharmaceutical activity.