THERMODYNAMICS OF BORATE ESTER FORMATION BY 3 READILY GRAFTED CARBOHYDRATES

Borate ester association constants for D-glycero-D-gulo-heptonamide (1 ), N-methyl-D-glucamine (2), and disorbitylamine (3) were derived from B-11 NMR observations. Significant electrostatic effects were observe d in the formation of berate esters with the ammonium derivative (2). B-11 NMR studies of 3 were consistent with the simultaneous formation of intramolecular tetradentate berate diesters and oligomeric chains o f 3 connected by intermolecular berate diesters. The process enthalpie s for formation of berate monoesters and diesters with 1 are Delta H(1 )degrees = -37.2 +/- 4.9 kJ/mol and Delta H(2)degrees = -19.6 +/- 2.5 kJ/mol, respectively. The corresponding process entropies are Delta S( 1)degrees = -51 +/- 17 J/mol/K and Delta S(2)degrees = -28 +/- 8 J/mol /K. (C) 1998 Elsevier Science Ltd. All rights reserved.