The synthesis of podands (acyclic crown ethers) including a 1,3-bis(1H-pyrazol-1-yl)propane unit in their molecule is described. The key step of this synthesis was a regioselective lipase-catalyzed transesterification of the dipyrazolic tetraethylester 1 with monomethylether polyethyleneglycols. The ionophoric properties of the podands 4a-d as carriers of cations were evaluated. Molecular modelling studies and quantum-chemical calculations were used in order to elucidate the superestructures of the complexes with ammonium cations. Enzymatic synthesis, ionophoric properties, and molecular modelling of new podands are descriled.

Financial support from the C.I.C.Y.T. (projects SAF 93-0753 and FAR 90-746) and a fellowship to one of us (M.F.) from the M.E.C. are gratefully acknowledged. We are also indebted to Novo Nordisk Bioindustrial S.A. for its generous gift of Lipozyme.