CONVERSION OF PROVITAMINS TO VITAMINS D 767 



It is believed that ring B is ruptured between positions 9 and 10. The 

 proof in this case is largely based upon the fact that this point of cleavage 

 has been proved for vitamin Dj. These 2 products are closely related, as 

 evidenced by the fact that both yield an identical dihydro derivative when 

 reduced with sodium in alcohol. ^^® 



The position of the double bonds is apparently shifted with the increase in 

 their number. They are believed to occur at the 10,5-, 6,7-, and the 8,9- 

 positions. This supposition is based largely upon the failure of tachysterol2 

 to form a ketone on oxidation. ^^'' Vitamin D2, when oxidized, has been 

 shown to form a ketone, C19H32O, which has been formed by the cleavage of 

 the double bond between carbons 7 and 8. Tachysterol2 therefore does not 

 have a double bond in this position. The structure which is in harmony 

 with these obsei-vations is given below: 



Tachysterol2 



On irradiation tachj'sterolj is converted into vitamin D2. It has no anti- 

 rachitic activity itself, and is about one-half as toxic as vitamin D2. As in 

 the case of the lumisterols, there are several tachysterols which are formed 

 from the respective provitamins. Thus, tachysterols has been prepared 

 from 7-dehydrocholesteroP*^ in the same manner as that by which tachy- 

 sterol2 is produced from ergosterol. Windaus and GiintzeP^® obtained 

 tachysteroU from 22-dih3^droergosterol by an analogous procedure. Tachy- 

 sterolsg and 4 can also be isolated by forming the addition products with 

 citraconic aldehyde. None has been prepared in crystalline form, al- 

 though the esters are crystallizable. 



The tachysterols are readily autoxidized. Their susceptibility to oxida- 

 tion is far greater than that of ergosterol or of any other irradiation prod- 

 ucts. The absolution spectrum is given in Figure 6. 



a. Dihydrotachysterol2. Dihydrotachysterola, also referred to as 

 A.T.IO (antitetany compound No. 10), is of considerable interest because 

 of its therapeutic value in deranged calcium metabolism. 



Dihydrotachysterol can readily be prepared by reduction of the 3,5- 

 dinitro-4-methyl benzoic acid ester of tachysterol with sodium ethoxide*^^ 



"6 M. Miiller, Z. physiol Chetn., 233, 223-234 (1935). 

 '" W. Grundmanii, Z. physiol. Chem., 252, 151-154 (1936). 



"« O. Dolmer and F. v. Werder (to Winthrop Chem. Co.), U. S. Patent No. 2,070,117 

 (Feb. 9, 1937; in Germany, July 27, 1934). 



