194 VITAMIN D GROUP 



Tachysterol exhibits considerable pharmacological activity. It is about 

 one-half as toxic as calciferol in producing kidney tubule calcification in 

 the mouse.'^^* For calcifying bone it is greatly inferior to calciferol although 

 still a potent agent. Windaus et al}^^ observed no antiricketic activity from 

 doses of 1 7 daily to rats, but higher doses were not explored. Meunierand 

 Thibaudet^^^" observed healing at the IO-7 level. This is about 500 times 

 the requirement of calciferol. Probably the antiricketic action was not 

 due to contamination with calciferol, for it was the same in samples of 

 tachysterol prepared the usual way and by the deiodination of iodocal- 

 ciferol. 



e. Precalciferol 



C28H44O. Probably four double bonds. Melting point of 3 , 5-dinitroben- 

 zoate 103° to 104°. [q:]d of 3,5-dinitrobenzoate = +45° in chloroform and 

 +30° in benzene, with mutarotation. Absorption maximum (of free form, 

 by graphic subtraction), at 265 mix. Molecular extinction coefficient at 

 265 mju = 9600. In solution, transforms into calciferol. 



In 1948-1949, when the irradiation series had come to be regarded as a 

 closed book, a renewed interest in the dark reaction came out of the studies 

 of Velluz and his associates. ^^^ Ergosterol in ether was irradiated under 

 nitrogen, the ether distilled off, the unconverted ergosterol frozen out of 

 alcohol, and the alcohol removed — all at a temperature below 25°. Without 

 heating, the resin was converted into 3 ,5-dinitrobenzoates, and the product 

 fractionated on alumina. The least strongly adsorbed fraction was crystal- 

 lized from ligroin, giving yields of precalcif eryl 3 , 5-dinitrobenzoate which 

 amounted to as much as 50% of the resin taken. That such an abundant 

 product should have been so long overlooked is surprising but understand- 

 able because it transforms itself into calciferol in solution, especially when 

 warmed. 



Precalcif eryl 3,5-dinitrobenzoate crystallizes from ligroin in fine pale- 

 yellow needles, m.p. 103° to 104°, obviously different from the bright yellow 

 massive crystals of calciferyl 3,5-dinitrobenzoate, m.p. 158° to 159°. The 

 ester upon saponification gives a non-crystalline free form of precalciferol, 

 which does not precipitate with digitonin and which gives the calciferol 

 color reactions of Pesez^** in reduced intensity. The absorption spectrum 

 of precalciferol is strikingly similar to that of calciferol, except that it is 

 only about half as intense. The curve (Fig. 9) shows no evidence of admix- 

 ture of other precursors of calciferol. When a benzene solution of precal- 



287 L. Velluz, A. Petit, G. Michel, and G. Rousseau, Compt. rend. 226, 1287 (1948); 



L. Velluz, A. Petit, and G. Amiard, Bull. soc. chim. France 15, 1115 (1948); L. 



Velluz and G. Amiard, Compt. rend. 228, 692, 853 (1949) ; L. Velluz, G. Amiard, and 



A. Petit, Bull. soc. chim. France 16, 501 (1949). 

 "8 M. Pesez, Bull. soc. chim. France 16, 507 (1949). 



