Abstract: A procedure for converting steroids characterized by presence of an 11.beta.OH group into potent corticoids having one or more substituents, such as 6.alpha.F, 16.alpha., 17.alpha.-hydroxy or isopropylidene dioxy, 16.alpha. or 16.beta. methyl, .DELTA..sup.1,4 ; by reacting the 11.beta.-hydroxy steroid with trichloromethyl siloxane steroid, thereby rendering the normally sensitive 11 substituent inert to the series of reactions which thereafter incorporate one or more of the desired above listed substituents into the steroid molecule. The siloxy group is then hydrolyzed to regenerate the 11.beta.-hydroxy substituent.Many of the trimethyl siloxy steroids are novel compounds.The siloxane may be selectively cleaved by reaction of the finely divided steroid with 40-60% aqueous HF.