IV. BIOCHEMICAL SYSTEMS 211 



derivatives are then oxidized witli alkaline permanganate to give the di- 

 carbonyl derivative of 2-keto-L-gulonic acid.^ "'^^ The free 2-keto acid 

 may he generated hy autohydrolysis or by means of dilute mineral acid, 

 after which it may be converted into L-ascorl)ic acid by either of the two 

 methods given above. 



It has also been found possible to bring about the direct conversion of 

 diisopropylidene 2-keto-L-gulonic acid^"*" and its ester-** into L-ascorbic 

 acid. By choosing the right solvent, this ingenious device enables L-ascorbic 

 acid to be crystallized directly from the reaction mixture. 



Success is also said to attend the acid-catalyzed conversion of molten 

 2-keto-L-gulonic acid to L-ascorbic acid.^^ 



IV. Biochemical Systems^ 



L. W. MAPSON 



A. SYNTHESIS OF ASCORBIC ACID 



Ascorbic acid is widely distributed throughout the animal and plant king- 

 doms. In animal tissue the highest concentrations are found in the suprarenal 

 cortex, eye lens, and liver tissues; in plants it is most abundant in the most 

 actively growing regions. Ascorbic acid occurs as such and in the oxidized 

 form, dehydroascorbic acid. It has also been alleged to occur in a combined 

 form as "ascorbigen," on the evidence that, when plant tissues are heated, 

 more ascorbic acid may be extracted than if the tissue is extracted by acid 

 in the cold.^''-^ This increase on heating has not been observed by 

 all workers, however, and the phenomenon has been explained as being 



" E. Boasson, S. Goldschmidt, and A. Middelbeck, Dutch Pat. 57,142 (1946). 



" Swiss Pat. 174,080 (1935); U. S. Pat. 2,039,929 (19.36); British Pat. 4.35,971 (1935). 



" T. Reichstein, British Pat. 446,548 (1937). 



" R. Pasternak and G. O. Cragwell, U. S. Pat. 2,185,383 (1940). 



" V. M. Berezovskil and L. J. StrePchunas, Zhiir. Priklnd. Khim. 22, 1113 (1949) 



[C.A. 45, 5627 (1951)]. 

 " H. W. Bassford, Jr., W. S. Harmon, and J. F. Mahoney, U. S. Pat. 2,462,251 (1949). 



28 A. H. Ruys and .J. F. Lemmens, U. S. Pat. 2,491,9.33 (1950). 



29 Dutch Pat. 59,710 (1947). 



' This section was prepared as part of the program of the Food Investigation Organi- 

 sation of the Department of Scientific and Industrial Research, England. 



i»B. Ahmad, Nature 136, 797 (1935); E. W. McHenry and M. Graham, ihid. 135, 

 871 (1935); E. J. Reedman and E. W. McHenry, Biochem. J. 32, 85 (1938); H. 

 Scarborough and C. P. Stewart, ibid. 31, 1874 (1937); Nature 142, 40 (1938). 



2 K. C. Saba, J. Indian Chem. Soc. 16, 511 (1939); B. C. Guha and P. N. Sen-Gupta, 

 ;Va<»re 141, 974 (19.38) ; J. C. Pal and B. C. Guha, J.7/(//("art T/jcm. Soc. 16, 481 (1939); 

 P. N. Sen-Gupta and B. C. Guha, ibid. 16, 496 (1939). 



