196 VITAMIN D GROUP 



separable via the 3,5-dinitrobenzoate into pure calciferol and two inactive 

 sterols. One of these, pyrocalciferol, was merely a thermal transformation 

 product, produced during the distillation. The other, "sterol X" (lumis- 

 terol), had come over from the original irradiation product. By the new 

 esterification technique calciferol could be obtained directly from the resin, 

 without distillation. 



While the isolation of calciferol was in progress in England, Windaus and 

 his associates in Germany were developing a different technique to the same 

 end. Windaus^^- and Windaus et alP^ reviewed their preliminary studies on 

 activation and announced that a crystalline vitamin D was obtained by 

 removing the inactive components of the resin by means of maleic or citra- 

 conic anhydride. Presently Linsert-^^ in 1931 obtained another crystalline 

 preparation somewhat different in its properties from the first. For a few 

 weeks Windaus and Liittrmghaus-^^ regarded these two preparations as 

 distinct forms of vitamin D, and called them vitamin Di and vitamin D2, 

 respectively. Soon, however, it was realized by Windaus et al}^^ that the 

 Linsert preparation was essentially identical with Bourdillon's pure cal- 

 ciferol, while the first German preparation was an addition compound of 

 calciferol with lumisterol. 



The name vitamin Di has been abandoned, but the name calciferol has 

 been retained, so that vitamin D2 and calciferol are now synonyms for the 

 pure product. The Commission on Nomenclature of Biological Chemistry 

 of the International Union of Pure and Applied Chemistry^^^ has adopted 

 the name ergocalciferol as another synonym, for the purpose of making 

 clearer the distinction from vitamin D3, which they call cholecalciferol. 



Callow's^' procedure of purifying calciferol via the 3,5-dinitrobenzoate 

 works so well that the properties and constants of calciferol are known 

 with better agreement than those of ergosterol. 



Calciferol crystallizes from methanol in clusters of colorless needles,^®^ 

 and from acetone in long prisms. ^^^ It is very soluble in most organic sol- 

 vents, but less so in methanol than in acetone. -^^ The solubility in acetone 

 amounts to 1 g. in 14 ml. at 7°.^"^ At 26° 100 ml. of acetone dissolves 25 g., 

 100 ml. of absolute alcohol 28 g., and 100 ml. of ethyl acetate 31 g. of cal- 

 ciferol.^^" 



The stability of calciferol has been reviewed and studied by Huber and 

 Barlow.^^^ Calciferol is even more unstable than ergosterol. Samples kept 

 under ordinary laboratory conditions show signs of decomposition in 2 or 



232 A Windaus, Proc. Roij. Soc. (London) B108, 568 (1931). 



293 A. Windaus, A. Luttringhaus, and M. Deppe, Ann. 489, 252 (1931). 



294 O. Linsert, cited, in a footnote, by A. Windaus, A. Luttringhaus, and M. Deppe, 

 Ann. 489, 252 (1931); U. S. Pat. 1,902,785 (1933). 



2" A. Windaus and A. Luttringhaus, Hoppe-Seyler's Z. physiol. Chem. 203, 70 (1931). 



298 A. M. Patterson, Chem. Eng. News 30, 104 (1952). 



297 W. Huber and 0. W. Barlow, /. Biol. Chem. 149, 125 (1943). 



