Analogs Prepared by Modification of Vitamin D and Related Compounds

Analogs Prepared by Modification of Vitamin D and Related Compounds 

DHV3-III. Cleavage of the intennediate boranes in these reactions by acetic acid was not very efficient making this a poor preparative method for these compounds. If the boranes were cleaved by alkaline hydrogen peroxide, however, high yields of the corresponding mixture of 19-hydroxy derivatives were obtained. One of these, (121), has shown interesting anti-vitamin D3 activity. 

Oxidation of la-hydroxy- or la,25-dihydroxyvitamin D3 with activated manganese dioxide results in the formation of the corresponding 1-oxo-previtamin (122) (139, 172), the reversion to the previtamin structure presumably occurring because of the additional stabilization of the linear triene system by the carbonyl function. Sodiiun borohydride reduction of (122) leads selectively to the ip-hydroxy previtamin (123) which on thermolysis affords the ip-hydroxyvitamin (124). Neither [(124), R = H] nor [(124), R = OH] has shown appreciable vitamin D-hke biological activity. 

Solvolysis of vitamin D3 tosylate in a buffered aqueous medium affords the A-ring bicyclic C-6(5) alcohol (125) in 60% yield 173, 175). Aqueous acid converts (125) into a mixture of vitamin D3 and trans- 

---

Analogs Prepared by Modification of Vitamin D and Related Compounds. .. 95... 

---