764 VIII. TROVITAMINS D AND VITAMINS D 



(i) Lumisteroh 



Lumisterol is the first product formed on irradiation of the provitamin. 

 It was originally referred to as "sterol X." Liimisterol2, C2gH430H, is the 

 predominant product formed when ei-gosterol is irradiatcd*^^ with light of 

 Avave lengths 285 to 313 m^u. After about 40% of the ergosterol has been 

 changed, lumisterol2 can readily be prepared in the following manner: 



The unchanged ergosterol is first removed by crystallization from methanol. The 

 methyl alcohol is removed by evaporation from the mother liquor. The residue is then 

 dissolved in acetone and the addition product of lumisterol^ and vitamin Do (formerly 

 called vitamin Di) is separated by crystallization. This addition product is readily 

 broken down by acetylation. When this mixture is subjected to fractional crystalliza- 

 tion from acetic acid, lumisterol-. acetate crystallizes out first. Pure lumisterol may be 

 prepared by saponification of the ester. 



Apparently, lumisterol is invariably formed on irradiation, and this step 

 cannot be by-passed. Lettre'** and Dimroth^*^ have shown that, even on 

 irradiation of ergosterol for a short period, lumisteroli is produced before 

 the next product, tachysteroh, is formed. Apparently, lumisterolo is a 

 necessary precursor of the latter compound, although Lettre states that it is 

 not yet certain whether tachysterol can be derived from ergosterol without 

 the intermediation of lumisterol. 



There is every evidence that lumisterolo is a compound closely related to 

 ergosterol. Molecular weight determinations and elementary analyses are 

 identical for these two compounds; the hydroxyl group is also present in 

 the irradiated product, as well as in the ergosterol, since lumisterol2 forms 

 esters. Three double bonds are present in lumisterol 2, as determined from 

 the reaction with perbenzoic acid and from catalytic hydrogenation.**^-'^" 

 One of these is on the side chain between carbons 22 and 23, since on 

 ozonolysis methylisopropylacetaldehyde is formed. '2- The other two 

 double bonds are conjugated, as can be judged from the absorption spec- 

 trum of lumisteroh. These must be on the same ring, which can be only 

 ring B or C. The ring system of lumisteroh and of ergosterol must there- 

 fore be identical. This conclusion is likewise based upon the demonstra- 

 tion that the same hydrocarbon, CisHie (7-methylcyclopentenophenan- 

 threne), results on selenium dehydrogenation of both sterols, '^^'^^^ and 

 upon the fact that the same toluene-tetracarboxylic acid"'^ is obtained on 

 nitric acid oxidation of lumisteroh and ergosterol. '^^'^^^ When lumisteroh 

 is treated with perbenzoic acid, a triol is formed which can be converted to a 

 diacetate. When the latter compound is acted upon by mercuric acetate, 



188 H. Lettre, Ann., 511, 280-291 (1934). 



188 K. Dimi-oth, Ber., 70, 1631-1636 (1937). 



190 K. Dimroth, Ber., 68, 539-542 (1935). 



19' F. Reindel and K. Niederlander, Ann., 482, 264-279 (1930). 



