((4,6-Bis((((2,2-dimethylpropanoyl)oxy)methyl)(methyl)amino)-1,3,5-triazin-2-yl)(methyl)amino)methyl pivalate AIDS-132493 AIDS132493 N2,N4,N6-Tripivaloyloxymethyl-N2,N4,N6-trimethylmelamine NSC626552