The present invention relates to a novel process for the esterification of N-acylated amino acids which contain an acid-labile keto protective group under alkaline conditions without using a polar aprotic solvent, in which the N-acylated amino acid with acid-labile keto protective group prepared in situ is esterified using an alkyl halide or a mono- or dialkyl ester of sulfuric acid.本發明關於一種用於在鹼性條件而沒有使用極性非質子性溶劑下酯化含有酸不穩定的酮保護基團之N-醯化胺基酸的新穎方法，其中原位製備之具有酸不穩定的酮保護基團之N-醯化胺基酸係使用鹵烷或硫酸單-或二烷基酯來酯化。
