12 CHOLINE 



Walz et al.^^ synthesized choline and acetylcholine labeled in the ethylene 

 chain with isotopic carbon-14. Acetylene-C^'', obtained from active car- 

 bonate in the usual manner,^^ was reduced to ethylene by reaction with 

 chromous chloride according to the method of Arrol and Glascock. ^^ The 

 labeled ethylene was converted to ethylene bromohydrin-l,2-C^^ with 

 N-bromoacetamide. The bromohydrin with excess trimethylamine in ether 

 yielded choline bromide with an 83 % yield based on the bromohydrin. 

 Dauben and Gee'^^ have published an alternative procedure starting with 

 carboxyl -labeled sodium acetate. This was converted to chloroacetic acid 

 which was esterified A^dth diazoethane. The resulting chloroacetate was 

 allowed to react with dimethylamine, and the product Avas reduced to 

 N , N-dimethylaminoethanol with lithium aluminum hydride. The substi- 

 tuted ethanol was further methylated with methyl iodide, and the choline 

 iodide converted into choline chloride with C^^ in the alcoholic carbon. 



An improved synthesis of phosphorylcholine has been described by 

 Baer.^^' ^^ The compound was prepared by the catalytic hydrogenation of 

 diphenylphosphorylcholine produced by the reaction of diphenylphosphoryl 

 chloride and choline chloride in pyridine. 



Glycerylphosphoric acid esters of choline have been prepared by Ravaz- 

 zoni and Fenaroli^^ and by Aloisi and Buffa^° from bromocholine picrate 

 and the silver a- and jS-glycerylphosphates. These authors suggest that 

 previous workers ma,y have confused the choline salts of the glycerylphos- 

 phates with the choline esters. The choline salts form readily and block 

 esterification. Baer and Kates^^' ^- prepared and studied the hydrolysis of 

 L-a-glycerylphosphorylcholine and noted a reversible shifting of the phos- 

 phoric acid between the a- and j8-carbons. 



Salts of choline and of the common acids, including acetic, carbonic, 

 hydrochloric, nitric, oxalic, picric, picrolonic, and sulfuric acids, are soluble 

 in water and in ethanol, whereas the acid tartrate, chloroplatinate, mono- 

 phosphate, and rufiinate are insoluble in ethanol. Double salts mth cad- 

 mium chloride and with zinc chloride are also soluble in water and insoluble 

 in ethanol. Double salts with gold chloride and with mercuric chloride are 

 insoluble in water. Other water-insoluble salts include the hexaiodide, 



83 D. E. Walz, M. Fields, and J. A. Gibbs, /. Am. Chem. Soc. 73, 2968 (1951). 



84 W. J. Arrol and R. Glascock, Nature 159, 810 (1947). 



86 W. J. Arrol and R. Glascock, J. Chem. Soc. 1950 Suppl, Issue 2, S 335. 

 86 W. G. Dauben and M. Gee, J. Am. Chem. Soc. 74, 1078 (1952). 

 8' E. Baer and C. S. McArthur, /. Biol. Chem. 154, 451 (1944). 



88 E. Baer, J. Am. Chem. Soc. 69, 1253 (1947). 



89 C. Ravazzoni and A. Fenaroli, Ann. chim. applicata 30, 318 (1940). 



90 M. Aloisi and P. Buffa, Biochem. J. 43, 157 (1948). 



91 E. Baer and M. Kates, /. Am. Chem. Soc. 70, 1394 (1948). 



92 E. Baer and M. Kates, /. Biol. Chem. 175, 79 (1948). 



