750 



VIII. PROVITAMINS D AND VITAMINS D 



are to be classed as potent provitamins T). Although the justification for 

 the general steroid structure has been discussed earlier (Chapter lY), proof 

 of the stmcture of the important provitamins D will be briefly outlined 

 below. 



(/) Erqodcrol {Provilamin D2) 



Ergosterol has an empirical formula of C2SH44O, as has been determined 

 by analysis of the crystalline 3,5-dinitrobenzoate and also of the halo- 

 genonitrobenzoate esters. "^'^'^ On catalytic hydrogenation, ergosterol 

 absorbs 6 hydrogen atoms, with the formation of ergostanol, C2sH5oO"^; 

 this indicates the presence of 3 double bonds. On the basis of the empirical 

 formula, ergosterol must contain 4 rings. This is readily proved by the 

 fact that it is converted to the Diels hydrocarbon, CigHie, on dehydrogena- 

 tion with selenium."^ In 1933, Rosenheim and King'^*^ identified this 



10000 - 



8000 



6000 



4000 



2000 



2200 



3000 



Fig. 1. Absorption spectra of 7-dehydrocholesterol and ergosterol in 

 ethanol according to Hogness et al.^°^ and Loofbourow.^" 



^^' J. R. Loofbourovv, Vitamins and Hormones, 1, 109-155 (1943). 



11^ A. Windaus, F. v. Werder, and B. G,schaider, Ber., 65, 1006-1009 (1932). 



*'^ A. Windaus and A. Liittringhaus, Nachr. Ges. Wiss. Gotlingen, Math, physik. 

 Klasse, HI, 4-7 (1932). 



'!« A. Windaus and O. Linsert, Ann., 465, 148-166 (1928). 



1" O. Diels and A. Karstens, Ann., 478, 129-137 (1930). 



"« O. Rosenheim and H. King, Chemistry & Industry, 11 (./. Sac. Chem. Ind., 52) 299- 

 301 (1933). 



