Synthesis, Characterization, and Alkali Metal Stability Constants of a New Bis(phosphotriester) Macrobicyclic Polyether Cryptand

Article abstract of DOI:10.1021/jo00104a026

The synthesis of a new bis(phosphotriester) macrobicyclic polyether cryptand, O=P3P=O (9), called phosphocrypt, and its acyclic tripodal precursor O=P3 (8) are described.The new cryptand 9 was synthesized by condensation of 8 and phosphoryl chloride which were simultaneously added under high dilution conditions in the presence of pyridine.The highest yield of 9 (30percent) was obtained with a final concentration of 3 mM in vigorously stirred methylene chloride.Both 8 and 9 form stable complexes with K(1+) and Rb(1+) in water.Log K_s values measured with a cation selective electrode for 8 are 3.6 and 3.0 and 3.7 and 3.6 for 9, respectively.The K_s values for phosphocrypt are 1000-fold greater than those of comparably sized nitrogen bridgehead cryptands. 1H and 13C NMR indicate 9 is flexible at 20 deg C.Molecular dynamics and mechanics calculations indicate that phosphocrypt has more cation-dipole interactions and more favorable conformational changes associated with complexation than comparably sized nitrogen bridgehead cryptands.