Abstract: The preparation of the crystalline a-amino acid N-carboxyanhydrides (Leuchs' anhydrides, NCA's) of the following amino acids is described: aspartic acid, asparagine, glutamine, 0-trimethylsilylserine, O-trimethylsilylthreonine, 0-trichloroacetylserine, histidine hydrobromide, 6-N-tert-butyloxycarbonyllysine, 0-(2-tetrahydropyrany1) tyrosine. All of these NCA's, except those of histidine and of 0-trichloroacetylserine, were shown to be useful in ...