18,19-dinor-vitamin D compounds

A compound having the formula:

• ##STR9## where X.sup.1 and X.sup.2, which may be the same or different, are each selected from hydrogen and a hydroxy protecting group, and where the group R is represented by the structure:
• ##STR10## where the stereochemical center at carbon 20 may have the R or S configuration, and where Z is selected from Y, --OY, --CH.sub.2 OY, --C.ident.CY and --CH=CHY, where the double bond may have the cis or trans geometry, and where Y is selected from hydrogen, methyl, --CR.sup.5 O and a radical of the structure:
• ##STR11## where m and n, independently, represent the integers from 0 to 5, where R.sup.1 is selected from hydrogen, deuterium, hydroxy, protected hydroxy, fluoro, trifluoromethyl, and C.sub.1-5 -alkyl, which may be straight chain or branched and, optionally, bear a hydroxy or protected-hydroxy substituent, and where each of R.sup.2, R.sup.3, and R.sup.4, independently, is selected from deuterium, deuteroalkyl, hydrogen, fluoro, trifluoromethyl and C.sub.1-5 alkyl, which may be straight-chain or branched, and optionally, bear a hydroxy or protected-hydroxy substituent, and where R.sup.1 and R.sup.2, taken together, represent an oxo group, or an alkylidene group, =CR.sup.2 R.sup.3, or the group --(CH.sub.2).sub.p --, where p is an integer from 2 to 5, and where R.sup.3 and R.sup.4, taken together, represent an oxo group, or the group --(CH.sub.2).sub.q --, where q is an integer from 2 to 5, and where R.sup.5 represents hydrogen, hydroxy, protected hydroxy, or C.sub.1-5 alkyl.