The present invention provides a process for the specific determination of pancreatic .alpha.-amylase in the presence of salivary .alpha.-amylase in body fluids by reaction with a system for the detection of .alpha.-amylase with the use of an inhibitor for salivary .alpha.-amylase, wherein, as substrate, there is used a compound of the general formula: ##STR1## in which R.sub.1 is a straight-chained or branched alkyl or alkoyl radical containing up to 6 carbon atoms, a cycloalkyl or cycloalkoxyl radical containing 3 to 6 carbon atoms or a benzoyl, benzyl or phenyl radical which is optionally hydrophilically substituted, R.sub.2 is a hydrogen atom or in which R.sub.1 and R.sub.2 together form a methylene bridge, the hydrogen atoms of which, independently of one another, can each be substituted by an alkyl radical containing up to 5 carbon atoms or a phenyl radical, Gluc is a glucose molecule, n is 1, 2 or 3 and X is an optically determinable residue.The present invention also provides a reagent for the specific determination of pancreatic .alpha.-amylase, as well as new compounds for use in the above process and reagent.