STRUCTURES OF VITAMINS D 



785 



Preparation of the Dimethyl Ester of the Maleic Anhydride Addition Product of 

 Vitamin D2 Acetate (XXV) 



The first reaction of the dimethyl ester (XXV) which is useful in estab- 

 lishing the structure of vitamin D2 involves catalytic hydrogenation fol- 

 lowed by ozonolysis of the dihydro compound (XXVI) so obtained. The 

 chief product of the reaction with ozone is a saturated ketone, C19H34O 

 (XXVII), as determined by analysis of its semicarbazone and of its oxime. 

 The number of carbons would seem to indicate that this compound con- 

 sists of rings C and D of the ergosterol molecule, the side chain, and the 

 angular methyl group located on C13 between rings C and D. Since no 

 methylisopropylacetaldehyde results on treatment with ozone, one must 

 conclude that the double bond in the side chain has previously been satu- 

 rated. 



Formation of a Ketone (XXVII) Following Ozonolj'sis of the Reduction Product 



(XXVI) of the Dimethyl Ester of the Maleic Acid Addition Product of 



Vitamin D2 Acetate (XXV) 



