SYNTHESIS OF THE GLYCERIDES 169 



Still another procedure by which a-monoglycerides have been synthe- 

 sized is by the direct esterification of glycerol in the presence of syrupy 

 phosphoric acid. This method has been reported by Schuette et al.^-^° for 

 the preparation of a-monoacetin and a-monobutyrin, but it is unsatis- 

 factory for acids containing more than four carbon atoms. A somewhat 

 different method has been used by Young and Black, ^^ who started with 

 the triglyceride. Thus, when trilaurin is heated with glycerol and sodium 

 phosphate under anhydrous conditions, a-monolaurin is formed. 



Baer and H. O. L. Fischer^- prepared optically active 1,2-acetoneglyc- 

 erols from d- and L-mannitol by splitting with lead tetraacetate followed 

 by reduction in ethyl acetate solution with hydrogen under pressure, using 

 the Raney nickel catalyst. From the optically active acetoneglycerol iso- 

 mers, the corresponding a-monoglj^cerides were prepared by the method of 

 E. Fischer, Bergmann, and Barwind.^ Several other technics which in- 

 volve direct esterification have also been proposed. ^^~^^ 



b. /3-Monoglycerides. The first satisfactory procedure for the prepara- 

 tion of /3-monoglycerides was introduced by Bergmann and Carter." 

 This method involves the catalytic reduction of esterified 1,3-benzylidene- 

 glycerol with hj'drogen under pressure, as sho\\'n below. Bergmann and 



HeC-O. HaC-O^^ HsCOH 



HCOH CHC6H5 """'^ -HCOOCfeCHCsHs "''^'^ i> HCOOCR 



I / pyridine I ^-^ I 



HjC-O^ HzC-O'^ H2C0H 



1 ,3-Berizylideiie- 2-Acyl-l,3- /3-Mouoglyceride 



glycerol benzj'lidene- 



glycerol 



Carter" prepared j8-monoacetin and /3-monopalmitin successfully by the 

 above procedures. Stimmel and Iving^^ have also found it satisfactory in 

 the preparation of the /3-monoglycerides of capric, lauric, myristic, and 

 stearic acids. 



An equally effective technic for preparing the symmetrical monoglycer- 

 ides involves the catalytic detritylation of the esterified 1,3-ditrityl ethers 

 of glyceroP^ according to the following scheme: 



9 H. A. Schuette and J. T. Hale, /. Am. Chem. Soc, 52, 1978-1981 (1930). 



'» P. G. Gilchrist and H. A. Schuette, /. Am. Chem. Soc, 53, 3480-3484 (1931). 



11 H. H. Young and H. C. Black, .7. .4m. Chem. Soc, 60, 2603-2605 (1938). 



12 E. Baer and H. O. L. Fischer, .7. Biol. Chem., 128, 463-473 (1939). 

 " I. Bellucci, Gazz. chim. Hal, 43, II, 283-30.5 (1913). 



'^ I. Bellucci and R. Manzetti, Alii accad. Lincei, 20, I, 125-128 (1911). 

 •* G. Gianoli, Seifensieder-Zlg., 39, 578 (1911); Chetri. AbsL, 5, 2573 (1911). 

 •6 T. P. Hilditch and J. G. Rigg, /. Chem. Soc, 1935, 1774-1778. 

 '" M. Bergmann and N. :\I. Carter, Z. physiol. Chem., 191, 211-221 (1930). 

 '8 B. F. Stimmel and C. G. Iving, J. Am. Chem. Soc, 56, 1724-1725 (1934). 

 19 B. F. Daubert, J. Am. Chem. Soc, 62, 1713-1714 (1940). 



