1-(1-Mesityl-3,3-diphenyl-2-phosphiranylidene)-2,2-dimethylpropyl triisopropylsilyl ether 3-(2,2-Dimethyl-1-((triisopropylsilyl)oxy)propylidene)-1-mesityl-2,2-diphenylphosphirane AIDS-150379 AIDS150379 NSC687327