414 V. CHEMISTRY OF PHOSPHATIDES AND CEREBROSIDES 



HX-O-CC^H,, HX-0-CC„H3, 



I Ox P? 0. I 0^ H0C2H4N(CH,),X 



HC-0-CC„H„ '-^-^ HC-O^CC„H„ ^-^ ^^ 



H^COH HjC-O-POg 



«,/3-Disteai-in a,/3-Distearin 



iiietaphosphoric 



acid ester 



0^ S 



H2C-0-CC,7H3B H^C-O-CCitH,, 



I 0^ I 0^ 



HC-O-CC.^Hj, " HC-O-CCi^Hj, 



HjC-O-P-OCjhUNlCHj), HjC-0-P-0C2H4N(CH3)j 

 ^OH X ' 1 



Lecithin Lecithin 



salt anhydride 



Another synthesis of lecithin is credited to Levene and Rolf,^^ who made 

 use of a lysolecithin prepared by the action of cobra (Naja tripudians) 

 venom on ordinary lecithin. ^^ Lysolecithin has one free hydroxyl group 

 on the glj^cerol, since one fatty acid residue of the original lecithin has been 

 lost by hydrolysis. From this compound, Levene and Rolf^' prepared 

 various lecithins by the addition of a stearyl, palmityl, benzoyl, acetyl, 

 oleyl, or elaidyl residue. 



The synthetic lecithins made by Griin and Limpacher^"' ''^ were shown 

 to have the same properties as the natural products. These workers^" 

 reported the preparation of a ;S-lecithin, also, using Q!,Q:'-diglyceride as the 

 starting material. The properties were practically identical with those 

 of the cc-lecithin. In view of the possibility of a migration of the acyl 

 group in the preparation of diglycerides to the Q:,/3-position, one wonders 

 whether an actual /3-lecithin was prepared in the above experiments. 

 In fact, the similarity in the products was so striking that the authors 

 themselves question whether or not the two products are identical. Ka- 

 bashima^^ prepared a dipalmityl-/3-lecithin which corresponded to natural 

 lecithin in solubility. 



(6) Properties of the Lecithins 



The lecithins are all characterized as translucent, parafl5n-like, colorless 

 substances when freshly prepared. On standing in air and light they 

 quickly become yellowish and then an opaque bro^vn. For the preparation 

 of pure compounds, it is essential that the light, and especially the air, be 

 excluded at all stages of the preparation. Lecithin is a waxy, plastic-like 

 material which has a dampish appearance; it is extremely hydroscopic. 



«2 P. A. Levene and I. P. Rolf, /. Biol. Chem., 60, 677-683 (1924). 



6' P. A. Levene, I. P. Rolf, and H. S. Simms, /. Biol. Chem., 58, 859-871 (1924). 



e* I. Kabashima, Ber., 71, 76-80 (1922). 



