AbstractThe value of several reagents capable of removing quantitatively the α‐amino protecting group of NPS‐aminoacyl‐ or peptidyl‐derivatives is assessed, by comparison with the reagents currently used,i.e.hydrogen chloride, RS–‐nucleophiles or alkyl thioamides, especially with regard to reaction specificity and end‐product solubility. New reagents proposed, 3‐nitro‐4‐mercapto‐benzoic acid, and its methyl ester, appear to optimize the numerous, and often competing, requirements. These were probed, under conditions suitable for both conventional and solid‐phase methods, on a series of model compounds, including diversely protected amino acids and short peptides, as well as for the actual synthesis of a triacontapeptide by the stepwi