Duphar International Research Bv

Wilhelmus R Overbeek

Sebastianus J Halkes

Luc J Vanmaele

Maurits E Vandewalle

Pierre J De Clercq

The invention relates to an adduct-aldehyde of the general formula ##STR1## wherein R is a hydrogen atom or an optionally etherified or esterified hydroxy group,

Adduct-aldehyde and its use for the preparation of vitamin-D compounds

The invention relates to a method of preparing 1 .alpha.-hydroxyvitamin D or 1 .alpha.-hydroxy-previtamin D compounds by hydroxylating the 1 .alpha.-position of an adduct of a previtamin D compound with a suitable dienophile, in which adduct optionally present hydroxy group or hydroxy groups is or are protected, if desired, and after removal of the protecting group or groups, isolating the 1 .alpha.-hydroxyvitamin D or 1 .alpha.-hydroxy-previtamin D compound. The invention also relates to 1 .alpha.-hydroxy-previtamin D compounds. The invention further relates to an adduct of a previtamin D or tachysterol compound with a dienophile of the general formula ##STR1## in which A' and B' are equal and represent methoxy groups or ethoxy groups, or in which A' and B' together constitute a phenylimino or o-phenylene group.

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Weesp, Netherlands

Wilhelmus R Overbeek