The present invention is concerned with an improved process for preparing .alpha.-fluoromethylamino acids.
A process for preparing fluoromethylamino acids from the corresponding hydroxymethylamino acids using SF.sub.4 in liquid HF to effect the fluorination is known (Kollonitsch et al., J. Org. Chem. 40 3808-9-1975). The process is referred to as fluorodehydroxylation.
It has now been discovered that the fluorode-hydroxylation of certain aryl substituted .alpha.-hydroxymethyl-.alpha.-amino acids is substantially improved by utilizing BF.sub.3 or AlCl.sub.3 as a co-reactant with SF.sub.4.