768 VIII. PROVITAMINS D AND VITAMINS D 



and subsequent saponification of the reduced product. Dihydrotachy- 

 sterolo can be crystallized readily, although this is not possible with unre- 

 duced tachysterol. 



On the basis of the absorption spectrum and of catalytic hydrogenation 

 experiments and the oxidative degradation reaction, von Werder^^ as- 

 signed the accompanying formula to dihydrotachystero^. The pure prod- 



Dihydrotachysteroh 



uct melts at 125-127°C. and has absorption maxima at 242, 251, and 261 

 Tan. 



Dihydrotachysterol2 is slightly effective as an antirachitic agent.^^ 

 This administration of this product results in an increase in blood calcium, 

 for which reason it has been used in the treatment of idiopathic hypopara- 

 thyroidism, as well as of the postoperative tetany following the injury or re- 

 moval of too great a portion of this gland. ^^^''^'"' Although tachysterol has a 

 slight tendency to increase the level of blood calcium, its effectiveness is 

 only about one-tenth that of the reduced product." 



(5) Vitamins D 



The vitamins D are the products formed by the further irradiation of the 

 various tachysterols. The distribution, properties, and structure of these 

 substances w411 be discussed in Section D of this chapter. 



The vitamins D are not necessarily the terminal products produced by 

 irradiation of the provitamins. When they are subjected to further action 

 by ultraviolet light, they rapidly lose their biological potency and are trans- 

 formed into products which have a toxic action. These products are toxi- 

 sterol, suprasterol I, and suprasterol II. It is not known whether these 

 products are formed in Sequence or whether each results as a primary de- 

 composition product of vitamin D when slightly different methods of treat- 

 ment are employed. 



(4) Toxisterols 



Toxisterol, also frequently called Substance 248 because of the promi- 

 nence of the absorption band at 248 m/x, was so named by Laquer and Lin- 



199 F. Holtz, Merck's Jahresber., 47, 20-23 (1934). 



200 F. Holtz, Klin. Wochschr., 13, 104 (1934). 



