THE CHEMISTRY OF COFFEE 



171 



must be correct since a study of preceding formulae and reactions 

 shows that methoxycaffeine is derived from chlorcafEeine which is 

 derived from caffeine. 



Complete synthesis of the alkaloid, caffeine, was obtained by Fisch- 

 er from dimethylalloxan which, when treated with neutral methyl 

 ammonium sulphite, forms an addition product which is converted 

 by concentrated hydrochloric acid irito trimethyluramil. This sub- 

 stance when heated with an aqueovis solution of potassium cyanate 

 yields tri-methyl-pseudo-uric acid which on being boiled with dilute 

 hydrochloric acid condenses to 1:3:7 trimethyluric acid or hydroxy- 

 caffeine. Hydroxycaffeine crystallizes in needles which melt at 

 345 °C. It is slightly soluble in cold water, alcohol, and ether. It 

 possesses both basic and acid properties. Hydroxycaffeine is converted 

 into chlorcaffeine by treatment with phosphorous pentachloride. 

 Chlorcaffeine, when reduced with zinc and hydrochloric acid, yields 

 caffeine. 



The complete synthesis of caffeine from dimethylalloxan as ex- 

 plained in the text is indicated by the following constitutional formu- 

 lae: 



CH, 



CO 



-N 



\ 

 CO 



CO CO 



N 

 I 



Dimethylalloxan 



CO 



/\ 

 / \ 



CH3 N CH— NH— CH3 



CO CO 



N 



I 

 CH3 



Trimethyluramil 



