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.
通过对以(â)-麻黄碱为手性助剂的不对称磷酰胺酸的δ-碳酰离子进行非对映选择性亲电氟化,合成了对映体纯的δ-一氟烷基膦酸4â9。氟化反应的非对映过量在很大程度上取决于碱和反离子的性质,脱氧率在 2%-72% 之间。通过柱层析法获得了非对映纯的δ±-氟磷酰胺酸盐。通过 X 射线晶体学确定了氟化膦酰酰胺酸盐的绝对立体化学结构。用 MeOHâTFA 除去麻黄碱助剂,然后用 TMSBr 处理,得到了δ-单氟烷基膦酸 4â9 ,产率为中等至良好。在手性碱奎尼丁存在下对手性膦酸 4â9 进行的 19F-NMR 分析表明,膦酸的ee值大于 97%。用 4â9 和蛋白酪氨酸磷酸酶 1B (PTP1B) 进行的抑制研究表明,R-对映体的抑制作用比相应的 S-对映体强约 10 倍,但比δ,δ-二氟类似物低 10 倍。本文讨论了造成这些差异的可能原因。