SYXTHESIS OF THE GLYCERIDES 171 



H2C0C(C6H5)3 HsCOClCfeHsli HaCOOCR 



HCOH ^^^^ ^ HCOOCR -4^^f^^! HCOH 



H^COH HjCOOCR H2COOCR 



l-Trit>lglyrerol l-Trityl-2,3- 1,3-Diglyceride 



diaej-lgl>-cerol 



The original Griin method which involves the treatment of 1,3-glycerol 

 disulfate with acyl chloiide-* is apparently somewhat unsatisfactory^^-" be- 

 cause of: (a) the high temperatures employed, (6) the uncertainties of the 

 structure of the intermediate halohydrins and disulfuric acid esters, and 

 finally because of (c) possibilities of rearrangement during the course of the 

 reactions. 



b. Unsymmetrical Diglycerides. Because of the unstable character 

 of the acyl group on the /3-position, a number of methods designed to 

 prepare Q:,/3-diglycerides have actually yielded the symmetrical derivatives. 

 This criticism apparently applies to the Grun procedure," as well as to 

 those of a number of other workers. ^^~^^ Golendeev^* has reported a 

 method for the synthesis of unsymmetrical diglycerides from allyl esters 

 where a shift from the /3- to the a'-carbon probably does not occur. This 

 is outlined below: 



CHz HsCOH H2COH 



lip HIO ' RCOOK ,,i/^,s--, 



CH ► HCI ► HCOOCR 



I I I 



H2COOCR H2COOCR HzCGOCR 



1-Acylacrolein l-Allyl-2- 1,2-Diglyceride 

 iodohydrin 



This would apparently be satisfactory for the preparation of mixed, un- 

 symmetrical diglycerides. 



The first entirely satisfactory procedure for making the unsymmetrical 

 diglycerides is that suggested by Daubert and King.'^ This involves the 

 catalytic detritylation of l,2-diacyl-3-tritylglycerol by hydrogen in neutral 

 solution as showii below. No shift of the acyl group from the /?- to the a'- 



K A. Griin, Ber., 88, 2284-2287 (1905). 



2« H. P. Averill, J. N. Roche, and C. G. King, /. Am. Chem. Soc, 51, 866-872 (1929). 



« A. Fairbourne, J. Chem. Soc, 137, 369-382 (1930). 



28 A. Griin and P. Schacht, Ber., 40, 1778-1791 (1907). 



^ F. Guth, Z. Biol, U, 78-110 (1903). 



» R. R. Renshaw, /. Am. Chem. Soc, 36, 537-545 (1914). 



" R. Delaby and P. Dubois, Compt. rend., 187, 767-769 (1928). 



« M. V. Humnicki and M. J. Lunkiewicz, Bull. soc. chim., 4-5, 422-428 (1929). 



" C. Weizmann and L. Haskelberg, Compt. rend., 18!), 104-106 (1929). 



" P. Golendeev, J. Gen. Chem. U. S. S. R., 6, 1841-1846 (1936); Chem. AbsL, 31, 

 4274 (1937). Cited bv A. W. Ralston, Fatty Acids and Their Derivatives, Wiley, New 

 York, 1948, p. 560. 



^ B. F. Daubert and C. G. King, J. Am. Chem. Soc, 61, 3328-3330 (1939). 



