Conformational analysis of 2- and 3-phosphoglyceric acids by 1H and 13C nuclear magnetic resonance spectroscopy

Abstract

The staggered rotamer populations about the C(2)–C(3) and C–O (phosphate) bonds of 2- and 3-phosphoglyceric acids (2PPG and 3PPG) have been estimated as a function of pH from ¹H–¹H, ¹H–³¹P, ¹³C–¹H, and ¹³C–³¹P vicinal coupling constants. For 2PPG in the pH range 5.0–10.8, between four and five conformations of the molecule may be significantly populated ( 10%). For 3PPG at low pH that conformer with the planar trans-arrangement of the C(2)–H and O–P bonds predominates and is possibly stabilised by intramolecular hydrogen bonding. At higher pH (9.8) there is an increasingly important contribution from that conformer with the C(2)–CO₂^– and O–PO₃^2– bonds in a planar trans-arrangement, and this conformer may be stabilised by a combination of intramolecular hydrogen bonding and the electrostatic interaction.