Synthesis of monofluoro- and difluoro- methylenephosphonate analogues of sn-glycerol-3-phosphate as substrates for glycerol-3-phosphate dehydrogenase and the X-ray structure of the fluoromethylenephosphonate moiety

The synthesis of the cyclohexylammonium salts of (1RS, 3S)-3,4-dihydroxy-1-fluorobutylphosphonic acid 3 and (S)-difluoro-3,4-dihydroxybutylphosphonic acid 4 is reported. These compounds are fluorinated phosphonate analogues of sn-glycerol-3-phosphate where the bridging phosphate ester oxygen is replaced by CHF and CF2 respectively. Kinetic studies are presented for oxidation with NADH linked glycerol-3-phosphate dehydrogenase, which reveal that the CHF-phosphonate 3 performs similarly to the natural substrate sn-glycerol-3-phosphate, and is a better substrate than the CF2-phosphonate 4. The study also reveals that the diastereoisomers of 3 (3a and 3b) are processed at different rates suggesting that the enzyme can discriminate the CHF stereogenic centres. A synthesis and X-ray crystal structure of 2 amino-1-fluoroethylphosphonic acid 7 is described which allows comparison of the geometry and conformation of CHF-phosphonate with that of analogous CH2- and CF2-phosphonates.