Facile Synthesis of dl-4,4-Difluoroornithine, dl-4,4-Difluoroglutamine, and γ-dl-4,4-Difluoroglutamyl-Containing Peptides: Regiospecific Addition of Nucleophiles to N-Cbz-di-tert-butyl-dl-4,4-difluoroglutamate
摘要:
The reaction of several nucleophiles with N-Cbz-protected di-tert-butyl-DL-4,4-difluoroglutamate was investigated as an approach to the synthesis of various fluorinated amino acids and peptides. The gamma-carboxyl group is highly activated by the two adjacent fluorine atoms, and nucleophilic reactions occurred exclusively at that carbonyl carbon. Further transformations of the reaction pro ducts re suited in the synthesis of DL-4,4-difluoroornithine, DL-4,4-difluoroglutamine, and gamma-DL-4,4-difluoroglutamyl-containing dipeptides.
Synthesis and Biological Evaluation of dl-4,4-Difluoroglutamic Acid and dl-γ,γ-Difluoromethotrexate
摘要:
DL-4,4-Difluoroglutamic acid (DL-4,4-F(2)Glu) and its methotrexate analogue, DL-gamma,gamma-difluoromethotrexate (DL-gamma,gamma-F(2)MTX), were synthesized and evaluated as alternate substrates or Inhibitors of folate-dependent enzymes. Synthesis of DL-4,4-F(2)Glu involved the nitroaldol reaction of ethyl nitroacetate with a difluorinated aldehyde ethyl hemiacetal as a key step. Attempted ligation of DL-4,4-F(2)Glu to methotrexate (MTX), catalyzed by human folylpoly-gamma-glutamate synthetase (FPGS), revealed that DL-4,4-F(2)Glu is a poor alternate substrate. DL-gamma,gamma-F(2)MTX was synthesized by a route proceeding through N-[4-(methylamino)benzoyl]-4,4-dinuoroglutamic acid di-tert-butyl ester followed by alkylation with 6-(bromomethyl)-2,4-pteridinediamine hydrobromide. DL-gamma,gamma-F(2)MTX was found to be neither a substrate nor an inhibitor of human FPGS. The fluorinated analogue of MTX, however, inhibits DHFR and cell growth with the same potency as MTX.