II. CHEMISTRY 193 



showed a substantial increase. These changes were not accompanied by 

 any significant loss of vitamin D potency. 



To explain the observed spectral change, Windaus et al}^ postulated the 

 existence of an unstable "protachysterol" which changes into tachysterol, 

 the intermediate characterized by intense absorption at 280 m^u. This ex- 

 planation does not account for the change in specific rotation, which was 

 opposite to what would be expected if tachysterol were being formed. 

 Interpretation of this dark reaction is further complicated by the subse- 

 quent discovery of precalciferol, described below. 



d. Tachysterol 



C28H44O. Four double bonds. Melting point of 3 , 5-dinitro-4-methyl ben- 

 zoate 154° to 155°. Absorption maximum at 280 myu, minor bands at 268 

 and 294 m/i. Molecular extinction coefficient at 280 m^ = 24,000. [a]^ = 

 — 70°, and [a]546i = —86.3° (in "Normalbenzin"). 



Tachysterol was isolated from activation resin by Windaus, Liittringhaus 

 and Busse'*^ in 1932, and its preparation and properties were described in 

 detail by Windaus, von Werder, and Liittringhaus.-^^ It got its name in 

 recognition of the speed (Gr. tachys) with which it reacts mth maleic or 

 citraconic anhydride to form an adduct useful in its separation. Tachysterol 

 has not been obtained in crystalline form, although tachysteryl acetate- 

 citraconic anhydride and tachysteryl 3 , 5-dinitro-4-methyl benzoate form 

 good crystals. Tachysterol is a source of trouble in the separation of irra- 

 diation products, because, besides failing to crystallize, it exhibits an ex- 

 ceptional affinity for oxygen, and the oxidation of calciferol is promoted by 

 its presence.^* It is insoluble in water, but easily soluble in the common 

 organic solvents, including methanol. It does not give a precipitate with 

 digitonin. It gives in modified form the color reactions of ergosterol. 



The structure of tachysterol (Fig. 13) has been elucidated largely through 

 the work of Miiller-*^ and Grundmann,-^^ supported by von Werder.-*^ In 

 tachysterol ring B is ruptured, with the formation of a fourth double bond. 

 Thus, like calciferol, it does not, in the strict sense, possess the sterol ring 

 structure. Its similarity to calciferol is further shown by the fact that, upon 

 reduction with sodium in alcohol, both compounds yield the same dihydro 

 derivative.'^* Tachysterol is converted into calciferol by irradiation,-*^ and 

 calciferol is converted into tachysterol by the introduction and removal of 

 an atom of iodine.-^^" 



283 A. Windaus, F. von Werder, and A. Luttringhaus, Ann. 499, 188 (1932). 

 28< M. Muller, Hoppe-Seyler's Z. physiol. Chem. 233, 223 (1935). 

 288 W. Grundmann, Hoppe-Sei/ler's Z. physiol. Chem. 252, 151 (1938). 

 286 F. von Werder, Hoppe-Seyler's Z. physiol. Chem. 260, 119 (1939). 

 286a p_ Meunier and G. Thibaudet, Compt. rend. 223, 172 (1946). 



