Small scale experimental model for the preparation of methyl ester of etodolac, the key intermediate in the synthesis of nonsteroidal drug etodolac, is thoroughly investigated in order to define the key parameters needed for its large scale production. Oxa-Pictet-Spengler reaction of 7-ethyltryptophol and methyl 3-oxopentanoate with inorganic acids as catalysts was monitored over time using HPLC method with UV detection. HPLC method for the simultaneous determination of 7-ethyltryptophol and the product was developed first. The conversion of 7-ethyltryptophol to etodolac precursor was performed using different molar equivalents of acid (1-5 with respect to the β-ketoester) and starting 7-ethyltryptophol of different degrees of purity. Kinetic profiles and optimal reaction times were in each case defined and key parameters selected.