A mixture of 4-(1,3-diethyl-2,3,6,7-tetrahydro-2,6-dioxo-1H-purin-8-yl)benzenesulfonic acid (5.0 g, 0.014 moles) and N,N-dimethylformamide (150 ml) is cooled to 0° and treated with thionyl chloride (3.3 g, 0.027 moles). When the addition is complete, the reaction mixture is permitted to warm to ambient temperature and stirred vigorously until a thick slurry results. To this slurry is added morpholine (20 g, 0.23 moles) in one portion. The resulting slurry is stirred one hour and poured into two liters of water. The resulting suspension is filtered, triturated with ethanol, and dried at 68° to yield 3.29 grams of 4-[[4-(1,3-diethyl-2,3,6,7-tetrahydro-2,6-dioxo-1H-purin-8-yl)phenyl]sulfonyl]morpholine, mp 354°-355° C.(d).
