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Abstract
Sucrose is an attractive molecule for chemistry because it is pure, abundant, inexpensive, and produced from renewable sources. Amoung its derivatives, sucrose esters are valuable targets for the chemical valorization of sugar, either as polymerizable derivatives, surfactants, or non-caloric fat substitutes.2 But although such potential commercially attractive sucrose derived molecules can be targeted, methods consistent with low-cost sucrouse diversification have still to be found. The issue of the solvent being critical, we have been interested in evaluating water as a possible solvent for some transformations of sucrose, and we report herein some preliminary results on the esterification of this sugar in basic aqueous medium.
1. Presented at the XVIII International Carbohydrate Symposium, Milan, Italy, July 21-26, 1996.
Notes
1. Presented at the XVIII International Carbohydrate Symposium, Milan, Italy, July 21-26, 1996.
A typical experiment consisted in adding neat octanoyl chloride (8.78 mmol, 1.5 mL) using an automatic syringe (0.1 mL/min flow rate) to a stirred 60% w/w sucrose aqueous solution (sucrose: 88 mmol, 30g, water: 20g) adjusted to pH 10 with 10N NaOH (pH-stat or manually). Reactions were monitored by TLC using a 56:20:20:4 mixture of dichloromethane, methanol, acetone and water as the eluent. After neutralization by adding 0.5N hydrochloric acid, water was added in order to get a less viscous solution, and the crude sucrose esters could be extracted with 1—butanol (2 or 3x 30 mL). After evaporation of the solvent, flash chromatography (same solvent as for TLC) allowed isolation first of the more substituted esters, then the diesters, and finally the monoesters. The average substitution degree was determined by comparing integration for the alkyl chain and sugar regions in 1H NMR spectra (d6-DMSO). Monoesters could be further purified by semi-preparative HPLC (nucleosil NH2, 0.5″ Ø, 93/7 MeCN/water, 7 mL/min, RI detection) and identified by 1H and 13C NMR spectroscopy. Sucrose reference data (D2O, 50.32 Mhz) δ 104.1 (C-2'), 92.6 (C-1), 81.8 (C-5'), 76.8 (C-3'), 74.4 (C-4'), 73.0 (C-3), 72.8 (C-5), 71.5 (C-2), 69.7 (C-4), 62.8 (C-1'), 61.8 (C-6'), 60.5 (C-6); 2-O-octanoyl sucrose: 176.5 (C=O), 104.4 (C-2'), 90.1 (C-1), 81.9 (C-5'), 75.9 (C-3'), 74.3 (C-4'), 73.0 (C-2), 72.8 (C-5), 70.8 (C-3), 69.7 (C-4), 62.8 (C-1'), 61.5 (C-6'), 60.5 (C-6), 34.2, 31.5, 28.7, 28.6, 24.6, 22.5, 13.9 (alk); 3-O-octanoyl sucrose: 176.8 (C=O), 104.3 (C-2'), 92.6 (C-1), 81.9 (C-5'), 76.9 (C-3'), 75.4 (C-3), 74.5 (C-4'), 72.8 (C-5), 69.9 (C-2), 68.0 (C-4), 62.8 (C-1'), 61.8 (C-6'), 60.5 (C-6), 34.6, 31.7, 28.9, 28.8, 25.0, 22.6, 14.0 (alk); 3'-O-octanoyl sucrose: 176.4 (C=O), 103.7 (C-2'), 92.0 (C-1), 82.3 (C-5'), 77.5 (C-3'), 73.4 (C-4'), 72.8 (C-3), 72.6 (C-5), 71.4 (C-2), 69.5 (C-4), 63.3 (C-1'), 62.2 (C-6'), 60.5 (C-6), 34.2, 31.4, 28.6, 28.4, 24.8, 22.4, 13.8 (alk); 4'-O-octanoyl sucrose: 175.8 (C=O), 104.6 (C-2'), 92.7 (C-1), 80.1 (C-5'), 76.4 (C-4'), 75.1 (C-3'), 73.0 (C-3), 72.9 (C-5), 71.5 (C-2), 69.5 (C-4), 62.7 (C-1'), 61.6 (C-6'), 60.4 (C-6), 34.2, 31.3, 28.5, 28.4, 24.7, 22.4, 13.8 (alk). Esterification position was determined through shift effects analysis