HYDROLYSIS PRODUCTS OF CEREBROSIDES 491 



Psijchosine sulfate (C24H47NO7 • ^^21^2804) is easily soluble in water and 

 benzene. It dissolves in hot methanol (1 part in 40 parts), from which it 

 slowly separates in wart-like crystals on the side of the flask when the solu- 

 tion is cooled. It is less soluble in eth.yl alcohol and insoluble in diethyl 

 ether. The aqueous solution shows a great tendency to foam. The 

 crystals sinter at 170°C. and begin to turn brown. They melt at 225°C. 

 with decomposition."^'' 



Since psj^chosine contains several asymmetric carbon atoms, it is optic- 

 ally active. Klenk and Hiirle^"^ report the following values for specific 

 rotation of the sulfate in pyridine solution: preparation from phrenosine, 

 -16.6° (19°C.); preparations from cerebroside mixture, -16.0° (19°C.), 

 and -16.5° (15°C.). 



Psychosine phosphate can be formed by the addition of alcoholic phos- 

 phoric acid to an alcohol solution of psychosine. It is soluble in hot water, 

 but separates as a gelatinous precipitate on cooling. \^Tien dissolved in 

 chloroform which contains alcohol, psychosine phosphate crystallizes in 

 long needles which are apparently a mixture of the mono- and the diphos- 

 phate. 



Psychosine picrate may be prepared from an aqueous solution of the sul- 

 fate by the addition of an equivalent amount of sodium picrate. ^"^ It 

 separates out as a resinous mass. 



Dihydropsychosine (C24H49NO7) is formed by hydrogenation of psycho- 

 sine in the presence of palladium. It contains two additional hydrogens 

 which are used to saturate the double bonds on carbons 4 and 5 of sphingo- 

 sine. Dihydropsychosine is insoluble in water, diethyl ether, and petro- 

 leum ether, but it dissolves readily in hot alcohol or acetone; on warming 

 with chloroform, it forms a gelatinous mass. Dihydropsychosine sulfate is 

 difiicultly soluble in alcohol. 



{2) The Ceramides 



Thudichum^^^ separated a second compound derived from the partial 

 hydrolysis of cerebroside, which he called aesthesine. The product was 

 similar to that of the original cerebroside molecule without the sugar mole- 

 cule. Klenk"" was unable to obtain aesthesine by the method employed 

 bj'' Thudichum. More recently these compounds have been prepared by 

 the partial breakdo\Mi of sphingomyelins: they are referred to as ceramides. 

 The best example of these compounds is lignocerylsphingosine, which has 

 been extensively discussed earlier (see pages 460-461 ) . Moreover, Klenk""^ 

 has been able to prepare cerebronyl-.Y-sphingosine from cerasine by a 

 method differing from that of Thudichum. 



a. Structure of Cerebronyl- A'^-Sphingosine. Cerebronyl- A'-sphingo- 

 sine has the same general formula as lignocerylsphingosine. It is a 



