202 VITAMIN D GROUP 



cholesterol. Thus a sample containing 59% cholesterol showed no change 

 after 5 weeks under the above conditions.^^^ The presence of much choles- 

 terol may be presumed to have been a factor in the survival of the provi- 

 tamin found in the brain of the mummy, mentioned above in another con- 

 nection. The substituted nitrobenzoates of 7-dehydrocholesterol are also 

 stable. Huber ei al.-^^ have recommended converting the provitamin into 

 its 3 , 5-dinitrobenzoate, both as a means of purifying it and preserving it, 

 so that fresh samples of the free provitamin can be had at any time merely 

 by subjecting the ester to a simple saponification. 



j. Lumisterolz 



C27H44O. Dimorphous: needles from acetone, melting point 87° to 88°; 

 mixed forms from methanol, melting point 63° to 64°. [a]^ — +197° in 

 chloroform. Absorption spectrum almost the same as that of lumisterol2. 



The initial irradiation product of 7-dehydrocholesterol is lumisterols, iso- 

 lated by Windaus et al.^^^ in 1937. It is distinguished from lumisteroU by 

 the fact that it does not form a molecular addition compound with its cor- 

 responding vitamin D. 



k. Tachysterolz 



C27H44O. Melting point of 3 , 5-dinitro-4-methyl benzoate 137°. Free form 

 has [afj = —11.5° in "Normalbenzin," but the ester is dextrorotatory. 

 Absorption spectrum like that of tachysteroh, but somewhat less intense. 



From the irradiation products of 7-dehydrocholesterol, tachysterols was 

 isolated by Windaus ei al}^^ in 1937. Like tachysteroh, it does not crystal- 

 lize, but forms crystallizable esters. 



I. Precalciferoh 



C27H44O. Melting point of 3 , 5-dinitrobenzoate 110° to 111°. [a] J? of 

 3 , 5-dinitrobenzoate = -|-52° in chloroform and +38.5° in benzene, with 

 mutarotation. 



Velluz et al.^^^ in 1949 obtained precalciferol in the form of its 3, 5-di- 

 nitrobenzoate, which crystallizes in pale yellow, thread-like needles not 

 exhibiting the dimorphism of the corresponding ester of vitamin D3. The 

 free form does not crystallize. The free (or ester) form exists in solution in 

 equilibrium with the corresponding free (or ester) form of vitamin D3, 

 with the vitamin (or ester) predominating. • 



m. Vitamin D3. Calciferoh. Cholecalciferol 



C27H44O. Three double bonds. Melting point 84° to 85°."i' ^^^ Broad ab- 

 sorption band with maximum at 265 m/i; molecular extinction coefficient 

 = 18,200 in alcohol or hexane.^^i [a]^" = +84.8° in acetone.-^^ 



316 L. Velluz and G. Amiard, Compt. rend. 228, 1037 (1949); L. Velluz, G. Amiard, and 

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



