Process and intermediates for preparing 1.alpha.-hydroxyvitamin D compounds

The compounds of claim 2 where X is a hydroxymethyl group.

Compounds having the formula:

• ##STR5## where each of R.sup.1 and R.sup.2 is selected from hydrogen or a hydroxy-protecting group, and where R is a side-chain having the structure:
• ##STR6## wherein each of R.sup.3 and R.sup.4 is selected from the group consisting of hydrogen, hydroxy or protected hydroxy, where R.sup.5 is selected from the group consisting of hydrogen, alkyl, hydroxy or protected hydroxy, and where R.sup.6 and R.sup.7 represent, independently, hydrogen, hydroxy or protected hydroxy, or when taken together, form a carbon-carbon double bond.

A process for preparing a compound having the formula ##STR7## where each of R.sup.1 and R.sup.2 is selected from the group consisting of hydrogen and an hydroxy-protecting group and where X represents a hydroxy-methyl or a carboxaldehyde group, which comprises

• treating a 1 alpha-hydroxy-7,8-dihydroxyvitamin D compound having the formula ##STR8## where each of R.sup.1 and R.sup.2 is selected from the group consisting of hydrogen and an hydroxy-protecting group and where R is a side-chain having the structure ##STR9## where each of R.sup.3 and R.sup.4 is selected from the group consisting of hydrogen, hydroxy or protected hydroxy, R.sup.5 is selected from the group consisting of hydrogen, hydroxy, alkyl and protected hydroxy, and R.sup.6 and R.sup.7 independently, represent hydrogen, hydroxy or protected hydroxy, or when taken together form a carbon-carbon double bond,
• with an oxidative reagent specific to the cleavage of vicinal diols thereby obtaining an aldehyde having the structure ##STR10## where R.sup.1 and R.sup.2 have the meaning defined above and X is a carboxaldehyde (--CHO) group and optionally subjecting said aldehyde to reduction with a hydride reducing agent to obtain the corresponding alcohol when X represents an hydroxy methyl group.