OCCUmiENCE AND STRUCTURE OF RELATED COMPOUNDS 



705 



Vitamin A acid has a biological potency in the same range as that of 

 vitamin A itself. When it was administered orally in peanut oil, as the free 

 acid, to vitamin-A-deficient rats, 4 ng. proved to be equivalent to one In- 

 ternational unit of vitamin A. However, when an aqueous solution of the 



1600 



1400 



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200 



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240 280 320 360 

 WAVE LENGTH IN M JJ. 



Fig. 3. The absorption spectra in ethanol of the following compounds: 



( — ) methyl ether of vitamin A; ( — ■ — ) ethyl ether of vitamin A; ( ) 



S-dehj-flromethyl ether of vitamin A; ( ) 5-dehydroethyl ether of vita- 

 min A.'*' 



sodium salt was injected subcutaneously, it was found that the bioi)otency 

 was approximately 50% of that of vitamin A alcohol, i.e., 0.6 jug. was found 

 to be equivalent to one International unit.^^ 



(3) Vilamin, A Ethers and Ilomologues 



A number of vitamin A ethers have recently been synthesized and have 

 been shown to possess considerable biological activity. Milas and co- 

 workers"^"^^^ were the first to prepare pure samples of the methyl and 



i'2 N. A. Milas, U. S. Patent Nos. 2,369,150 to 2,369,168 (Feb. 13, 1945). 

 "3 N. A. Milas, U. S. Patent Nos. 2,382,085 and 2,382,086 (Aug. 14, 1945). 

 "* N. A. Milas, E. Sakal, J. T. Plati, J. T. Rivers, J. K. Gladding, F. X. Grossi, Z 

 Weiss, M. A. Campbell, and H. F. Wright, /. Am. Chem. Soc, 70, 1597-1607 (1948) 



