6-Benzyl-4-(methylthio)-6-phenyl-5,6,7,8-tetrahydro-6.lambda.~5~-phosphinino[4,3-d]pyrimidine 6-Benzyl-6-phenyl-5,6,7,8-tetrahydro-6.lambda.~5~-phosphinino[4,3-d]pyrimidin-4-yl methyl sulfide AIDS-127811 AIDS127811 NSC192981