used in the preparation and characterization of sundry steroid phosphate and phosphonate esters, as well as some P1,P2-disteroid pyrophosphates. An attempt to prepare cholest-3,5-dien-3-yl dialkyl phosphate by a vinylogous Perkow reaction from 6-bromocholest-4-en-3-one yielded only dienenones. As a model for P1,P2-disteroid pyrophosphate (and steroid phosphate) behavior in solution, the neutral crystalline