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-1-yl)propane unit. Their structures have been unequivocally elucidated after their H-1 and C-13 NMR spectra and WEPT experiments. (C) 1997 Elsevier Science Ltd.