- Probing the stereochemistry of E. coli 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (phenylalanine-sensitive)-catalyzed synthesis of KDO 8-P analogues
-
The five-carbon phosphorylated monosaccharide analogues, D-arabinose 5-phosphate, D-ribose 5-phosphate, and 2-deoxy-D-ribose 5-phosphate, were separately condensed with (Z)- and (E)-[3-2H]-phosphoenolpyruvate (PEP) in the presence of Escherichia coli 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAH 7-P) synthase (phe) to give in the case of (Z)-[3-2H]-PEP (3S)-[3-2H]-3-deoxy-D-manno-octulosonate 8-phosphate, (3S)-[3-2H]-3-deoxy-D-altro-octulosonate 8-phosphate, and (3S)-[3-2H]-3,5-dideoxy-D-altro-octulosonate 8-phosphate, respectively, whereas incubation with (E)-[3-2H]-PEP gives the corresponding (3R)-monosaccharides. These results are in complete agreement with the observed facial selectivity of DAH 7-P synthase for its normal substrates D-erythrose 4-phosphate and PEP and provide direct evidence that DAH 7-P synthase (phe) catalyzes the si face addition of the C3 of PEP to the re face of C1 of the phosphorylated monosaccharides tested. Products formed by DAH 7-P synthase (phe)-catalyzed condensation of (Z)- and (E)-[3-F]-PEP with E 4-P were completely characterized by 1H and 19F NMR analysis for the first time. Results of our studies suggest that disappearence of the double bond between C2 and C3 of PEP and formation of a bond between C3 of PEP and C1 of the phosphorylated monosaccharide tested occur in concert during the DAH 7-P synthase-catalyzed condensation reaction.
- Sundaram, Appavu K.,Woodard, Ronald W.
-
p. 5891 - 5897
(2007/10/03)
-
- Synthesis of (E)- and (Z)-bromobis(triphenylphosphine)palladium and the X-ray Crystal Structure Determination for the E-Isomer
-
We report the preparation of (E)- and (Z)-bromobis(triphenylphosphine)palladium from the corresponding ethyl (E)- and (Z)-3-bromo-2-propenoate and the X-ray crystal structure determination for (E)-bromobis(triphenylphosphine)palladium.The (E)-palladium complex was reduced to (E)-3-phosphoenolpyruvate by treatment with a mixture of trifluoroacetic acid-d/trifluoroacetic anhydride under strict anhydrous conditions.The 1H-NMR spectrum of the E-isomer obtained from the reduction of the palladium complex was identical to the 1H-NMR spectra of (E)-3-phosphoenolpyruvate previously prepared by two different synthetic strategies.The X-ray structure of the palladium phosphoenolpyruvate analogue is the first X-ray structure of any 3-substituted phosphoenolpyruvate analogue reported and along with its synthesis and transformation interrelates the stereochemistry of several 3-substituted phosphoenolpyruvate analogues.
- Dotson, Garry D.,Kampf, Jeffrey W.,Woodard, Ronald W.
-
p. 5774 - 5778
(2007/10/02)
-