STRUCTURE OF PROVITAMINS D 753 



This is readily identified by its semicarbazone or dinitrophenylhydrazone 

 derivative, as well as by its conversion to methylisopropylacetic acid on 

 oxidation. These reactions indicate that the side chain of ergosterol con- 

 tains an unsaturated linkage between carbons 22 and 23. 



,S=o 



H3C CH, 



Ergosterol Methylisopropjl- 



acetaldehyde 



The presence of an hydroxy! group on ergosterol is indicated by its 

 ability to form esters. The fact that the alcohol group is attached to posi- 

 tion 3 in common with other sterols is indicated by the demonstration by 

 Fernholz and Chakravorty^^'' that the same 3-acetoxy-nor-allocholanic acid 

 is obtained on oxidation of acetylated ergostanol as is derived from dihydro- 

 cholesterol acetate. 



The final proof of the structure of ergosterol necessitates the establish- 

 ment of the position of the double bonds. One of these has already been 

 shown to occur in the side chain between carbons 22 and 23. The second 

 one is in the 5,6 position, which is the location of the single unsaturated 

 linkage of cholesterol.'^^ This has been proved by a complicated set of 

 reactions involving oxidation with perbenzoic acid to form ergostadiene- 

 triol monobenzoate.'^*^ This compound contains one secondary and one 

 tertiary alcohol group. After saponification and acetylation, an ergosta- 

 diene-triol diacetate is formed which is readily reduced to ergostene-triol 

 diacetate by catalytic hydrogenation. On treatment with hydrochloric 

 acid, the single double bond in the latter compound rearranges, and the 

 resulting triol is readily saturated." This becomes ergostane triol after 

 saponification. The latter contains two of the hydroxyl groups in a,^ 

 position as determined from the Criegee reaction with lead tetraacetate. 

 On chromic acid oxidation, an hydroxy-diketone is formed which, on treat- 

 ment with hydrochloric acid, splits out water to produce a diketone. The 

 unsaturated diketone ergostenedione is readily transformed into the cor- 

 responding saturated diketone, ergostadione. The pyridazine derivative 

 can be formed from this by treatment with hydrazine. Since one ketone 

 group is known to be in position 3 in place of the original hydroxyl group, 

 the second one must be in position 6, since the pyridazine will be formed 



'2^ E. Fernholz and P. X. C'hakravortv, Ber., 67, 2021-2026 (1934). 



'25 A. Windaus, H. H. Inhoffen, and S. v. Reichel, Ann., 510, 248-259 (1934). 



i2« A. Windaus and A. Luttringhaus, Ann., 481, 119-131 (1930). 



