490 V. CHEMISTRY OF PHOSPHATIDES AND CEKEBKOSIDES 



are placed on carbons 1 and 3, it is not yet certain which particular hydroxyl 

 of the sphingosine is involved. 



b. Preparation of Psychosine. Psychosine can be prepared by the 

 Klenk raethod^^^ by the hydrolysis of phrenosine with barium hydroxide. 

 In this method, 4 g. of the pure cerebroside is heated with 80 ml. of 10% 

 barium hydroxide for 7 hours in a boiling water bath. After cooling, the 

 precipitate, consisting chiefly of unhydrolyzed phrenosine, is filtered off, 

 washed, and dried in vacuo; the residue is pulverized and boiled with 50 

 ml. of 96% alcohol. The unchanged phrenosine which precipitates on 

 ceding is filtered off, and the process is repeated. About 1 g. of phrenosine 

 remains unhydrolyzed. The combined alcoholic extracts are condensed to 

 about 30 ml. under reduced pressure. Psychosine is precipitated as the 

 sulfate by the addition of dilute alcoholic sulfuric acid. Care must be taken 

 to avoid an excess of the acid. The psychosine sulfate which precipitates is 

 purified by recrystallization from 500 ml. of absolute alcohol. The yield of 

 psychosine from 4 g. of phrenosine amounts to about 1.65 g. The separa- 

 tion of the psychosine from cerebroside mixtures containing appreciable 

 amounts of unsaturated acids is somewhat more complicated. 



The free base can be prepared from the sulfate by hydrolysis of an 

 aqueous solution with barium hydroxide, followed by filtration of the 

 precipitate, which is a mixture of psychosine and barium sulfate. After 

 washing and drying, the precipitate is treated with hot alcohol, and the 

 insoluble barium sulfate is filtered off. Psychosine precipitates from the 

 alcoholic solution after it is concentrated to a few milliliters, and is allo\\ed 

 to stand in the cold. 



c. Properties of Psychosine. Psychosine is a white powder which is 

 soluble in ethyl and methyl alcohol, but which is insoluble in diethyl ether 

 and petroleum ether. It swells up to form a gelatinous mass in hot ben- 

 zene or chloroform. Psychosine is difficult to obtain in crystalline form. 

 However, it can be prepared in long thin needle-like crystals by the follow- 

 ing procedure: A solution in 20 parts of a mixture of equal parts of chloro- 

 form and ethyl alcohol is mixed with 100 volumes of petroleum ether, and 

 the mixture is warmed carefully until the precipitate is dissolved. When 

 the solution is cooled, psychosine crystallizes practically quantitatively 

 and almost immediately in a homogeneous needle-like for-m. The crystals 

 sinter at 110°C., turn yellow at 160°C., melt at about 215°C., and decom- 

 pose at 223°C.=*^^ 



Psychosine reacts ciuantitatively with the Van Slyke reagent for amino 

 nitrogen. ^^■^ It produces a purple color with concentrated sulfuric acid,-^^ 

 and a positive Molisch reaction. On hydrolysis, it gives rise to sphingosine 

 and galactose: 



C24H47NO7 ) CsHiaNOo + CslIiaUe 



Psychosine Sphiiigosiuo. Galactose, 



64.1)% 39.0% 



