Preparation of chiral α-monofluoroalkylphosphonic acids and their evaluation as inhibitors of protein tyrosine phosphatase 1B
作者:Christopher C. Kotoris、Wendy Wen、Alan Lough、Scott D. Taylor
DOI:10.1039/a908086d
日期:——
Enantiomerically pure α-monofluoroalkylphosphonic acids 4â9 were synthesized by diastereoselective electrophilic fluorination of α-carbanions of asymmetric phosphonamidates bearing (â)-ephedrine as a chiral auxiliary. The diastereomeric excess of the fluorination reaction was highly dependent on the nature of the base and counterion with deâs ranging from 2â72%. Diastereomerically pure α-fluorophosphonamidates were obtained by column chromatography. The absolute stereochemistry of the fluorinated phosphonamidates was established by X-ray crystallography. Removal of the ephedrine auxiliary using MeOHâTFA followed by treatment with TMSBr afforded α-monofluoroalkylphosphonic acids 4â9 in modest to good yields. 19F-NMR analysis of the chiral phosphonic acids 4â9 in the presence of the chiral base quinidine indicated that the phosphonic acids were obtained in greater than 97% ee. Inhibition studies with 4â9 and protein tyrosine phosphatase 1B (PTP1B) revealed that the R-enantiomers were approximately 10-fold more potent inhibitors than the corresponding S-enantiomers, but 10-fold less potent than their α,α-difluoro analogues. Possible reasons for these differences are discussed.