NATURAL WAXES 



350 



with difficulty in cold methanol and oils, but it dissolves somewhat more 

 easily in cold chloroform (0.2%) and to a much greater extent in the hot 

 solvent (3.1%). It is also quite readily dissolved either by cold (2%) or 

 by boiling ether (3.6%). Anhydrous ergosterol melts at 163 °C., and the 

 form containing one molecule of water melts between 166° and 183° C. 

 The best preparations of the hydratcd form melt at 168 °C.^"^ Ergosterol 

 can be distilled without decomposition under a high vacuum (0.4 mm.) at 

 250°C. The specific rotation of a 2% chloroform solution at 20 °C. is 

 — 132°. On irradiation with ultraviolet light, it is destroyed. Ring B 

 splits between Cg and Cio with formation of vitamin D3 (see Chapter VIII 

 for discussion of this reaction). Ergosterol is also decomposed by such 

 oxidizing agents as concentrated halogens or potassium permanganate. 

 Mineral acids cause an isomerization of the molecule. When it is hydro- 

 genated in the presence of selenium, a hydrocarbon is formed '"^''"^ which is 

 identical with the compound produced when cholesterol is similarly 

 treated. ^^^ Ergosterol also forms a difficultly soluble digitonide. Charac- 

 teristic absorption bands, which are largely independent of the solvent, 

 have peaks at 260, 269, 281, and 293 m^, with the maximum at 281 m//. 

 Table 9 gives data on some of the derivatives. 



Table 9 

 Properties of Some Ergosterol Esters 



Ergosteryl 



M 



'^^r 



[«)d 



Remarks 



Slightly sol. in cold ethanol, readily sol. 



in ethyl acetate and ether 



Platelets, difficultly sol. in ethanol and 



ether 



Needles, difficultly sol. in most org. 



solvents except readily sol. in pyridine 



b' Dihydroergosterol : 22,23-Dihydroergosterol (C28H45OH) assumes 

 considerable importance, since it, also, is a provitamin (D4). Although it is 

 much less widely distributed in nature than is ergosterol, this product has 

 been isolated from natural sources. Ruiz'^^ prepared it from ergot, and it 

 occurs to the extent of 2-5% in yeast. ''^ Its structure is proved by its 

 synthesis from ergosterol. *^^ On hydrogenation of this sterol, after pre- 



^' C. E. Bills and E. M. Honeywell, /. Biol. Chem., 80, 15-23 (1928). 



^'SL. Ruzicka, M. W. Goldberg, and G. Thomann, Helv. Chim. Acta, 16, 812-832 

 (1933). 



'»" L. Ruzicka, AI. W. Goldberg, G. Thomann, and E. Brandenberger, Nature, 132, 

 643 (1933). 



'!» O. Diels and A. Karstens, Ann., 478, 129-137 (1930). 



"1 A. S. Ruiz, Anales real acad. farm., 3, 201-231 (1941); Chem. Ahstr., 38, 503 (1944). 

 Cited by W. L. Ruigh, Ann. Rev. Biochem., I4, 232 (1945). 



"" A. Windaus and R. Langer, Ann., 508, 105-114 (1933). 



