Molecular recognition of xanthine alkaloids: First synthetic receptors for theobromine and a series of new receptors for caffeine

Synthetic receptors (H3, H4, H5 and H6) are designed and synthesised for the first time for theobromine, a xanthine alkaloid used as a diuretic. The synthesis of the receptor H6 is achieved by Co(PPh3)3Cl-mediated homocoupling of 3-(ethoxycarbonyl)benzyl bromide 12 under mild conditions. New caffeine receptors (H7, H8 and H9) are designed and synthesised. The binding results of theobromine and caffeine (both by NMR and UV studies) are reported.