GUANIN. 383 



Brom-guanin, C^H^BrNjO, was prepared by Fischer and Eeese in 

 1883, and is analogous to brom-caffein, adenin, and hypoxanthin. 

 The hydrochlorid dissociates at ordinary temperature. By the action 

 of nitrous acid it is changed into brom-xanthin just as brom-adenin is 

 converted into brom-hypoxanthin. On prolonged heating with strong 

 hydrochloric acid it yields 2-amino 6.8 di-oxy purin (Fischer). 



Acetyl guanin, CjH^Np.CO.CHj, was prepared by Wulff by 

 heating dry powdered guanin with acetic anhydrid. It forms small, 

 colorless, silky needles which are very difficultly soluble in cold 

 water — in about 4,000 parts ; more difficultly in cold alcohol and 

 almost insoluble in ether. It is soluble in about 150 parts of boil- 

 ing water ; less easily in hot alcohol. It is easily soluble in dilute 

 acids, alkalis, and ammonia, especially on warming. On heating 

 with acids and alkalis it is completely saponified. From a solution 

 in cold dilute sodium hydrate it is precipitated unchanged by car- 

 bonic acid. It is likewise unaffected by boiling water. At 260° it 

 is apparently unchanged. 



Propionyl guanin, CjH^NjO.CO.CHj.CHj , was also prepared by 

 Wulff by heating dried guanin with propionic anhydrid. Only a 

 small part of the guanin enters into combination. It forms peculiar 

 crystals, which under the microscope appear as rather long plates or 

 scales, frequently with notched edges. The precipitate is very volum- 

 inous and when dried forms a light, felt-like, white mass having 

 a mother of pearl luster. Its properties correspond to the acetyl 

 compound. It is likewise apparently unaffected at 260°. 



Benzoyl guanin, CjH^NjO.CO.CgH, . Benzoic anhydrid reacts even 

 less energetically than propionic anhydrid on guanin, and only a 

 very small quantity of the ester forms. It appears as small round 

 masses, which consist of fine stellate or bunched needles. It is 

 difficultly soluble in hot water and alcohol, insoluble in ether. At 

 very high temperature it decomposes with brown coloration. It is 

 rather resistant to the action of boiling water, but is readily saponi- 

 fied by hot dilute acids. Attempts to obtain this compound by the 

 action of benzoyl chlorid on guanin or on guanin-silver failed. 



Alkyl derivatives of guanin. Fischer and Reese attempted un- 

 successfully to prepare alkyl derivatives of guanin by the action of 

 methyl iodid on the lead and silver compounds of guanin. Wulff 

 endeavored to prepare benzyl guanin in the same way that Thoiss 

 made benzyl adenin, but failed. Even heating benzyl chlorid with 

 guanin in the presence of sodium hydrate failed. Attempts to pre- 

 pare a dimethyl derivative were likewise resultless. Recently, how- 

 ever, Fischer has been able to prepare synthetically the 7-methyl 

 and the 1-7-dimethyl guanins. The former is identical with 

 Kriiger and Salomon's epiguanin which will be next described. The 

 latter on oxidation yields methyl guanidin, and corresponds to 

 heteroxanthin. 



