Disclosed are novel A.sub.2B adenosine receptor antagonists of Formula I: A compound of the formula: ##STR00001## wherein: R.sup.1 is optionally substituted alkyl or a group --Y-Z, in which Y is a covalent bond or optionally substituted alkylene, and Z is optionally substituted cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted heterocyclyl, optionally substituted alkenyl or optionally substituted alkynyl, with the proviso that when Y is a covalent bond Z cannot be alkenyl or alkynyl; and X is oxygen, sulfur, or NH--, or a pharmaceutically acceptable salt, ester, or prodrug thereof. The compounds are particularly useful for treating asthma and diabetic retinopathy.