¹³C NMR and mass spectrometry studies have been used to demonstrate that the inhibition of α-chymotrypsin by N-sulfonylhydroxymethylpyrrole inhibitors (10) is non-covalent. Hydroxyalkylpyrroles in which an electron-withdrawing group (acyl substituent) is introduced at the alternative C2 position have been synthesised and also shown to inactivate α-chymotrypsin. SAR studies on this class suggests that the incorporation of phenylalanine at C2 is favoured, however, there is little gain in introducing a hydrophobic substituent at C5.