P-O donor action from carboxylate anions with phosphorus in the presence of hydrogen bonding. A model for phosphoryl-transfer enzymes.
A series of phosphorus compounds (1-3) containing anionic carboxylate groups were synthesized by treatment of the respective neutral precursor acid forms B-D with amines, which also served to introduce hydrogen-bonding interactions. The compounds, subjected to X-ray structure analysis, resulted in hexacoordinated anionic phosphoranates 1A and 1B, a pseudo-trigonal-bipyramidal anionic phosphine (2), and a trigonal-bipyramidal anionic phosphine oxide (3). The structures revealed that P-O donor coordination was present in all members of the anionic series 1-3 and resulted in stronger interactions than existed in the precursor neutral acid forms B-D as measured by the presence of shorter P-O distances. Evaluation of the energies of the donor interactions relative to the energies of the hydrogen bonds that were present showed that the donor energies now exceeded the hydrogen bond strengths. (31)P chemical shifts indicated that the basic coordination geometries were retained in solution. Both 1A and 1B are chiral and exist as racemates. The results suggest that mechanisms of phosphoryl-transfer enzymes should benefit by taking into account donor interactions at phosphorus by residues at active sites in addition to the inclusion of hydrogen bonding. Reference is made to specific phosphoryl-transfer enzymes.
Chandrasekaran
A
A
Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003-9336, USA.
Day
Roberta O
RO
Holmes
Robert R
RR
D001665:Binding Sites; D002264:Carboxylic Acids / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D006860:Hydrogen Bonding; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008968:Molecular Conformation; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry*; D010770:Phosphotransferases / Q000737:chemistry*
D002264:Carboxylic Acids; D010758:Phosphorus; D010770:Phosphotransferases; D010100:Oxygen