Molecular recognition of pyrimidine and xanthine bases by lipophilic calixarenes derived from resorcinol and pyrogallol

Two lipophilic calixarenes, derived from resorcinol (R1) and pyrogallol (R2 ), were investigated as receptors for pyrimidine and xanthine bases in extr action experiments. Extraction abilities sequence for R1 in chloroform is: cytosine > uracil > thymine, whereas for R2: thymine > uracil > cytosine. F or xanthine bases, the appropriate extraction abilities sequence is: for R1 - dyphylline > theophylline > theobromine and R2 - theobromine > theophyll ine > dyphylline. Competitive molecular recognition of pyrimidine and xanth ine bases by lipophilic calixarenes, incorporating resorcinol and pyrogallo l units, was studied in extraction experiments in various solvents. Xanthin e bases: theophylline, theobromine and dyphylline were extracted more easil y into toluene and chloroform than to diethyl sebacate. Among pyrimidine ba ses, no clear pattern of extraction was observed: uracil was extracted most effectively to toluene phase, thymine - into diethyl sebacate, cytosine in to - chloroform.