744 VIII. PROVITAMINS D AND VITAMINS D 



recently been prepared by Ruigh.'^^ Campesterol is a C28 steroid which was 

 originally isolated by Fernholz and MacPhillamy.'^^ Activated 7-dehydro- 

 stigmasterol, which differs from ergosterol only by having an ethyl group 

 on the C24 atom in place of the methyl group, is practically devoid of vita- 

 min D activity/^ although it is frequently considered to be in this cate- 

 gory." Moreover, the provitamin D activity is not abolished by conver- 

 sion of the A^^-ethenoid linkage of ergosterol into the oxide nor by epimer- 

 ization of the hydroxyl group on the third carbon. Thus, both ergosterol- 

 22-oxide'^ and epi-ergosterol have been shown to be active provitamins D. 

 This is also true for irradiated epi-7-dehydrocholesterol, prepared from epi- 

 cholesterol, which has been found to have one-tenth the activity of vita- 

 min Ds.''^ Lumisterol, an irradiation jjroduct of ergosterol, has also been 

 reported to have a positive provitamin D activity,**'^ while another synthetic 

 product, dihydrotachysterol or A.T.IO (antitetany substance No. 10 — see 

 pages 767, 768), possesses some antirachitic action without further activa- 

 tion.^^ It has been claimed that mussel provitamin D produces a vitamin D 

 with a potency as great as that of vitamins Do or Ds*^ ; its structure is not as 

 yet known. Slight provitamin D activity has also been ascribed to 

 A^'''-androstadiene-3,17-dioF*''^^ and to 3-hydroxy-5,7-choladienic acid.** 



Although it would appear that most of the natural forms of the vitamins 

 D have been identified, it seems quite probable that many synthetic pro- 

 vitamins D and vitamins D will come to our attention in the future. The 

 historical background of the rickets problem was reviewed by Park,*^ while 

 Bills*'' has considered the subject of vitamin D from the historical stand- 

 point. The latter review includes an excellent bibliography up to 1935. 

 Reed et alF' also publi-shed a monograph on vitamin D. 



B. PROVITAINIINS D 



The provitamins D are considered to be those compounds which, when 

 subjected to a satisfactory procedure for their activation, are converted 



'^ W. L. Ruigh, ./. Am. Cheni. Soc, 64, 1900-1902 (1942). 



75 E. Fernholz and H. B. MacPhillamy, J. Am. Chem. Sue, 63, 1155-1156 (1941). 



76 O. Linsert, Z. physiol. Chem., 2.'4, 12.5-128 (1936). 



" H. R. Rosenberg, Chemistry and Physiology of the Vitamins, Inter.science, New York, 

 1945. 



'8 K. Dimroth and J. Paland, Ber., 72, 187-190 (1939). 

 " A. Windaus and J. Naggatz, Ann., 5.^2, 204-218 (1939). 



80 I. M. Heilbron and E. R. H. Jone.s, Ann. Rev. Biochem.. U, 135-172 (1940). 



81 F. V. Werder, Z. physiol. Chem., 260, 119-134 (1939). 



82 A. G. Boer, J. van Niekerk, E. H. Reerink, and A. van Wijk, U. S. Patent No. 

 2,163,659 (June 27, 1939). 



83 A. Butenandt, E. Hausmann, J. Paland, D. v. Dreyler, and U. Meincrty, Bcr., 

 71, 1316-1322 (1938). 



84 G. A. D. Ha.sle\vood, Biochem. J., 33, 454-456 (1939). 

 8* E. A. Park, Phi/siol. Revs., 3, 106-163 (1923). 



86 C. E. Bills, Physiol. Revs., 15, 1-97 (1935). 



8' C. I. Reed, H. G. Struck, and I. E. Stack, Vitamin D, Univ. Cliicago Press, 1939. 



