Abstract: The invention provides methods for preparing the various isomeric forms of 25-hydroxyvitamin D.sub.3 -26,23-lactone utilizing cyanohydrin formation with readily prepared steroid materials followed by actinic radiation of the products and recovery of the desired 25-hydroxyvitamin D.sub.3 -26,23-lactone.The invention also provides new intermediate compounds in their various isomeric forms derived during the process for preparing the said vitamin D.sub.3 lactones.25-Hydroxyvitamin D.sub.3 -26,23-lactone is recognized as having vitamin D-like activity and is believed to play an important role in the regulation of calcium and phosphate levels in the animal and human organism. The present invention provides a convenient method for preparing the various isomeric forms of this compound.

Abstract: A method for isotopically labeling carbon-6 of vitamin D and 5,6-trans-vitamin D compounds which comprises reducing the corresponding 6-oxo-cyclovitamin with a tritio- or deutero-borohydride and subjecting the reduction product to acid-catalyzed solvolysis.The 6-labeled compounds find application in the elucidation of vitamin D metabolism and function and in vitamin metabolite analyses.

Abstract: This invention relates to isotopically labeled vitamin D compounds, including radiolabeled vitamin D compounds of high specific activity, methods for their preparation, and novel intermediates in their synthesis.The radiolabeled vitamin D compounds are characterized by high specific activity (up to 160 Ci/mmol) with the process providing a facile and convenient method for synthesizing such compounds.

Abstract: The invention provides new vitamin D derivatives as well as new intermediate compounds derived during the processes for preparing such new derivatives. The new derivatives have been identified as 1.alpha.-hydroxy-25-keto-27-nor-vitamin D.sub.3 and its acylates.1.alpha.-hydroxy-25-keto-27-nor-vitamin D.sub.3 expresses excellent vitamin D-like activity and would find ready application as a substitute for vitamin D compounds in the treatment of disease states evincing calcium-phosphorous imbalance.