AbstractThe possibility of the preparation of some ester derivatives of dimethylxanthines from 1‐theobromine‐ and 7‐theophylline acetic acids and 7‐(2‐hydroxyethyl)‐theophylline by DCC/DMAP‐mediated esterification under mild conditions was studied. The structures of the compounds synthesized and by products isolated were demonstrated by microanalyses, UV‐, IR‐, and1H NMR data. Acute toxicity assessment of the compounds on mice showed that compounds4, 5, 6, and7are less toxic than aminophylline. A pharmacological study of thein vitrobroncholytic effect (IC50and pD2values) of the derivatives and aminophylline showed that the new compound4(1,2,3,6‐tetrahydro‐1,3‐dimethyl‐2,6‐dioxo‐7H‐purine‐7‐acetic acid 2‐(1,2,3,6‐tetrahydro‐1,3‐dimethyl‐2,6‐dioxo‐7H‐purine‐7‐yl)ethyl ester) has a strong bronchodilating effect on serotonine‐ and acetylcholine‐induced spasm in guinea pig trachea. The same compound does not influence barbiturate — induced hypnosis and locomotor activity, unlike to t