8,8,10,10-Tetra(1-aziridinyl)-3-phenoxy-1,2,4,5,7,9,11-heptaaza-3,6.lambda.~5~,8.lambda.~5~,10.lambda.~5~-tetraphosphaspiro[5.5]undeca-6,8,10-triene 3-sulfide AIDS-137694 AIDS137694 NSC642783