HYDROLYSIS PRODUCTS OF CEREBROSIDES 



489 



lated by Thierf elder and Ivlenk** must be modified to one of the following: 



H '['"3 

 CH5(CH2),2CH = CHC-C-CHj 



HO H 

 I 

 HC — 



I 

 HCOH 

 I 

 HOCH 



i 

 HOCH 



HC 



I 

 CH.OH 



CH5(CH2),2CH=CHC-C-CHzOH 

 H 



HC 



I 

 HCOH 



I 

 HOCH 



HOCH 



HC 



I 

 CH^OH 



It is now certain that .siniihir i)syt'ho.sine molecules occur as a result of 

 the partial hydrolysis of glucosidocerebrosides. The possible formulas for 

 the glucosidopsychosincs are: 



H r^ 



CH,(CH,),,CH=CHC-C-CH» 



OH H O 

 I 

 HC- 



HCOH 



I 

 HOCH 



1 

 HCOH 



I 

 HC 



NH, 



CHa(CHj),5,CH=CHC-C-CH20H 



H 

 I 

 HC 



HCOH 



I 

 HOCH 



I 

 HCOH 



I 

 HC 



CH.OH 



CH,0H 



a. Structure of Psychosine. The combination of sphingosine and galac- 

 tose has been shown to be a glucosidic one. The fact that psychosine 

 cannot reduce the ordinary aldehyde reagents mdicates that the aldehyde 

 group in the sugar exists in combination. The galactose cannot be com- 

 bined with the amino group of sphingosine, since psychosine reacts with 

 nitrous acid and the amino group must therefore certainly be unattached. 

 The proof that galactose is combined with only one of the hj'droxjd groups 

 of sphingosine inatrue glucoside linkage wasfurnished by Klenk and Ha.rle,^'" 

 who isolated a monomethoxydihydrosphingosine when dihydropsychosine, 

 A\hich had previously been methylated, was hydrolyzed with dilute sulfuric 

 acid. A further proof of the glucosidic type of union is afforded by the 

 demonstration by Pryde and Humphreys*^'^ that galactose exists in psycho- 

 sine with an oxygen bridge from carbons 1 to 5. Such a cyclic structure is 

 essential if one is to assume a glucoside structure. It was sho\ATi that, on 

 hydrolysis of a methylated cerebroside mixture, 2,3,4, 6-tetramethylgalac- 

 tose was present in the hydrolysis mixture.^" Klenk and Harle believe 

 that the combination between galactose and sphingosine occurs through 

 the hydroxjd on carbon 2 of the base. However, in view of the recent revi- 

 sion in the structure of sphingosine according to which the hydroxy 1 groups 



