II. CHEMISTRY 147 



duction of the keto to the hydroxy sterols. They also obtained a product 

 patent^i on 7-hydroxycholesterol. Barr et alP made 7-hydroxycholesterol 

 by oxidizing cholesteryl hydrogen phthalate with permanganate. Hasle- 

 wood^^ found that better yields of the monobenzoate of the dehydro sterols 

 were obtained when the dibenzoate of the 7-hydroxy sterols was treated 

 with boiling dimethylaniline instead of being heated dry in vacuo. Rosen- 

 berg^^ patented the use of organic bases in general for this purpose. Winter- 

 steiner and Ruigh^^ discovered that the dibenzoate, when treated at room 

 temperature with sodium methylate in methanol, undergoes an unexpected 

 partial hydrolysis, the acyl group at position 3 being removed, while the 

 acyl group at position 7 remains. The resulting 7-monobenzoate of the 

 hydroxy sterol can then be heated in dimethylaniline to give the desired 

 7-dehydro sterol in superior yield and purity. 



Wintersteiner^^ made 7-hydroxy sterols by treating stabilized colloidal 

 solutions of the original sterol with molecular oxygen, and Wintersteiner 

 and Bergstrom" obtained good yields of 7-ketocholestero] and 7-hydroxy- 

 cholesterol by this means. Kramli^^ prepared 7-ketocholesteryl acetate by 

 anodic oxidation, reduced it to 7-hydroxycholesterol with sodium methylate 

 in methanol-benzene, and dehydrated the product to 7-dehydrocholesterol 

 by boiling with concentrated oxalic acid solution. The dehydration pro- 

 cedure was admittedly open to improvement, and the product was not well 

 characterized. Horvath and Kramli^^ obtained, among other products, 7- 

 dehydrocholesterol from cholesterol by the action of Azoiohacter and^° a 

 good yield of 7-hydroxycholesterol by the action of Proaciinomyces roseus. 



Milas and Heggie^^ have patented the dehydrogenation of cholesterol and 

 similar sterols by treatment with a wide variety of agents. Their examples 

 were confined to cholesteryl acetate, which they dehydrogenated with qui- 

 none, chloranil, sulfur, diphenyl sulfide, benzaldehyde, methylene blue in 

 the presence of light, and the succinodehydrogenase of beef heart. Their 

 best example (with quinone) showed a yield of 20 % of provitamin. Mazza 



'1 A. Windaus and F. Schenck, U. S. Pat. 2,098,985 (1937). 



^2 T. Barr, I. M. Heilbron, E. G. Parry, and F. S. Spring, J. Chem. Soc. 1936, 1437. 



" G. A. D. Haslewood, J. Chem. Soc. 1938, 224; Biochem. J. 33, 454 (1939). 



7" H. R. Rosenberg, U. S. Pat. 2,209,934 (1940). 



" O. Wintersteiner and W. L. Ruigh, /. Am. Chem. Soc. 64, 1177 (1942); U. S. Pat. 



2,411,177 (1946). 

 '« O. Wintersteiner, U. S. Pat. 2,400,380 (1946). 

 " O. Wintersteiner and S. Bergstrom, /. Biol. Chem. 137, 785 (1941); S. Bergstrom 



and O. Wintersteiner, ibid. 141, 597 (1941); 145, 309, 327 (1942). 

 ->» A. Krdmli, Arch. Biol. Hung. 17, 337, 343 (1947). 

 ^» J. Horvdth and A. Krdmli, Nature 160, 639 (1947). 

 8" A. Krdmli and J. Horvdth, Nature 162, 619 (1948); 163, 219 (1949). 

 *' N. A. Milas and R. Heggie, J. Am. Chem. Soc. 60, 984 (1938); U. S. Pat. 2,260,085 



(1941). 



