Purine Derivatives of Various Activities

The most suitable conditions for TLC-separation of the naturally occurring xanthine derivatives, caffeine, theobromine and theophylline, are basic silica gel layers with neutral solvents or neutral silica gel 

I = Silica gel G layer, buffered to pH 6.8 (25 g silica gel G slurried with 50 ml of a mixture of equal amounts of 0.2 M primary potassium phosphate and 0.2M secondary sodium phosphate solutions). Chloroform-96% ethanol (90 + 10) as solvent. 

II == Silica gel G layer. Acetone-chloroform-n-butanol-25% ammonium hydroxide (30 + 30 + 40 + 10) solvent. Chromatography in shaUow dishes as chambers, at normal saturation. 

III = Silica gel G layer. Ethyl acetate-methanol-acetic acid (80 + 10 + 10) as solvent. 

3- Dimethyl-7 - [2 -(l -methyl-2 -phenyl-ethylamino)-ethyl]-xanthine 

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