Optical resolution, absolute configuration, and activity of the enantiomers of proxyphylline

The enantiomers of proxyphylline have been separated via their corresponding camphanates. Synthesis of (+)-proxyphylline from theophylline and (S)-propylene oxide derived from (S)-lactic acid established the absolute configuration of the (+) and (-) isomer as S and R, respectively. The activity of the enantiomers as cyclic nucleotide phosphodiesterase inhibitors was tested in human lung tissue homogenate. No differences were found either between the two enantiomers or between the enantiomers and racemic proxyphylline.