| abstract |
The invention relates to a process for the preparation of compounds (I), in which A and R2 are defined in claim 1 of the invention, by reaction of phenyl-glycine (VII) in the presence of alkanol with 1.05 to 1 , 3 moles of alkali hydroxide, and by reaction of the mixture with an acid having a pH value higher than 4.3, or by reaction of (VII) with an equivalent amount of alkaline salts of acids having a higher pH value at 4.3, and by condensation of the salt of amino acids obtained in the presence of alkanol using a compound (VIII) - R1 is defined in claim 1 of the invention - at the boiling point of mixing the reaction, then continuously removing water from the reaction mixture by binary or ternary azeotropic distillation. The compound thus obtained can then optionally be reacted with a reactive trifluoro-methane sulfonic acid derivative. |