CONVERSION OF PROVITAMINS TO VITAMINS D 765 



dehydrolumistei'ol results. ^^^ All of these reactions are analogous to those 

 given b}^ ergosterol. The conclusion seems justified that the double bonds 

 must occur between carbons 5,6 and 7,8. '^'^ 



Several reactions of lumisterolz are markedly different from those of ergo- 

 sterol. In the first place, lumisteroU does not form an addition product 

 with digitonin: moreover, no bimolecular compound results when lumis- 

 terol is irradiated in the presence of eosin. Finally, upon complete hy- 

 drogenation of lumisterol^, the hexahydro compound formed differs from 

 hexahydroergosterol. 



The difference between lumisterolo and ergosterol is now known to be 

 one of stereoisomerism. The point of difference cannot be on C3, since 

 pyrocalciferol, in which an epi arrangement on C3 occurs, yields a bimolecu- 



Lumisteroh 



lar compound with eosin. It is now certain that the structural dif- 

 ference between ergosterol and lumisteroLi is due to a steric difference in the 

 position of the methyl group on carbon 10. 



Lumisterolg^"*' and lumisterol4''''' have been prepared from 7-dehydro- 

 cholesterol and 22-dihydroergosterol, respectively. They closely resemble 

 lumisterol2, except that they fail to form addition products with their cor- 

 responding vitamins as is the case with lumisterolo. This addition com- 

 pound of lumisterol2 and vitamin D2 has the molecular ratio 1:1. Lumi- 

 sterol2 can be converted into vitamin D2 by irradiation, although it is de- 

 void of any biological activity. It is presumed that lumisterols and lumi- 

 steroh Avould yield vitamins D3 and U4 on additional irradiation. 



(2) Tachysterols 



Tachysterol, C28H43OH, is the second known product which is formed in 

 the progressive activation of provitamin Do. It was named tachysterin by 

 Windaus, Liittringhaus, and Busse."^ The name denotes its outstanding 

 property, i.e., the speed with which it reacts. Lumisterol presumably 

 3'ields first a protachysterol, which is very unstable and which has not been 



>" I. M. Heilbron, F. S. Spring, and P. A. Stewart, J. Chem. Soc, 1935, 1221-1223. 

 1" I. M. Hoilhron and F. S. Spring, Chetnistrij & Industry, 13, 795-797 (1935). 

 1'^ A. ^Yindaus, A. Liittiingliaus, and P. Bus.sc, Xachr. Ges. Wiss. Gottingen, Math, 

 phiisik. Klasse, III, 150-159 (1932). 



