Regioselective lipase catalyzed synthesis of diester crowns. New asymmetric macrocycles containing a 1,3-bis(1H-pyrazol-1-yl)propane unit

Abstract

Regioselective lipase catalyzed intramolecular transesterification of dipyrazolic tetraester 1 with di-, tri- and tetraethyleneglycol afforded symmetric and, in smaller amounts, asymmetric diester crowns including a 1,3-bis(1H-pyrazol-l-yl)propane unit. Their structures have been unequivocally elucidated after their 1H and I3CNMR spectra and INEPT experiments.