Synthesis of sucrose carbonates in aqueous medium

Abstract

Mono-O-allyloxycarbonyl sucrose derivatives have been prepared by reaction of unprotected sucrose with allyl chloroformate in pure water, whereas the presence of a co-solvent is necessary in the case of the reaction with octyl chloroformate, for which polysubstitution is favoured because of hydrophobic interactions.

References

1. R. Khan, Pure Appl. Chem., 1984, 56, 883; L. Hough, in Carbohydrates as Organic Raw Materials, ed. F. W. Lichtenthaler, VCH, Weinheim, 1991, p. 33.
2. P. Boullanger, P. Chatelard, G. Descotes, M. Kloosterman and J. H. van Boom, J. Carbohydr. Chem., 1986, 5, 541; P. J. Kocienski, Protecting Groups, Georg Thieme Verlag, Stuttgart, 1994.
3. General methods and typical procedure used for the preparation of sucrose carbonates. To a stirred aqueous solution of sucrose (28 mmol, 9.6 g in different solvents) adjusted with a pH-Stat (METROHM 736 GP Titrino) and cooled to about 0 °C (ice–salt bath) was added allyl or octyl chloroformate (7 mmol) within 15 to 40 minutes (automatic syringe). The reaction was considered finished when the pH value (addition of base) was measured constant over 10 minutes. The solution was neutralized with 5%(w/w) aqueous acetic acid. The crude mixture was either extracted with butan-2-ol and analysed by analytical HPLC or evaporated to dryness and submitted to silica gel chromatography (as a solid mixture adsorbed on silica gel). Two fractions were isolated: polysubstituted products (R_f= 0.60–0.80 for allyl and 0.90–1.00 for octyl); monosubstituted products (R_f= 0.40–0.50 for allyl and 0.60–0.75 for octyl). Sucrose did not elute in this solvent. Eluent for the TLC and flash chromatography: chloroform–methanol–acetone–water (56∶20∶20∶4). HPLC: Nucleosil NH₂ column with CH₃CN–water (90∶10), flow: 0.8 ml min^–1, RI detection.
4. Data for mono-O-allyloxycarbonyl sucrose derivatives. Elemental analysis for C₁₆H₂₆O₁₃·0.7H₂O: Calc.: C, 43.8; H, 6.3. Found: C, 43.8; H, 6.1. m/z(FAB+) 427 (M + H⁺). Carbon NMR ([²H₆]DMSO, 75 MHz) and analytical HPLC allowed the identification of some isomers after partial separation by flash chromatography. Consistent effects on chemical shifts were observed (ca.+ 7 ppm for the carbon directly connected to the carbonate function, and ca.–2 ppm for the neighbouring carbon atoms). 3-O-Allyloxycarbonyl sucrose: δ 154.7 (C=O), 132.6, 118.3 (C=C), 104.3 (C-2′), 91.7 (C-1), 82.9 (C-5′), 80.5 (C-3), 77.0 (C-3′), 74.4 (C-4′), 72.7 (C-5), 69.7 (C-2), 67.7 (CH₂-allyl), 67.5 (C-4), 63.0, 62.3, 60.1 (C-6, 1′, 6′); 4′-O-allyloxycarbonyl sucrose: δ 154.2 (C=O), 132.3, 118.8 (C=C), 104.7 (C-2′), 92.5 (C-1), 81.6 (C-4′), 80.2 (C-5′), 75.1 (C-3′), 73.0 (C-3,5), 71.9 (C-2), 69.9 (C-4), 68.4 (CH₂-allyl), 62.6, 61.6, 60.5 (C-6, 1′, 6′); mixture of 6, 1′ and 6′-O-allyloxycarbonyl sucrose: δ 154.6, 154.5, 154.3 (C=O), 132.4, 132.3, 118.8, 118.6 (C=C), 104.5, 104.2, 102.0 (C-2′), 92.3, 92.0, 91.9 (C-1), 83.1, 83.0, 79.2 (C-5′), 77.2, 76.6, 76.5 (C-3′), 74.9, 74.7, 73.5 (C-4′), 72.9–73.1 (C-3,5), 71.8, 71.7, 71.6 (C-2), 70.3, 70.0, 69.9 (C-4), 69.6, 68.2, 68.1, 67.1, 65.9 (carbonated primary carbons of sucrose and CH₂-allyl), 63.0, 62.7, 62.3, 61.8, 61.0, 60.7 (non-carbonated C-6, 1′, 6′).
5. A. Lubineau, J. Augé, H. Bienaymé, Y. Queneau and M.-C. Scherrmann, in Carbohydrates as Organic Raw Materials II, ed. G. Descotes, VCH, Weinheim, 1993, p. 99; A. Lubineau, H. Bienaymé, Y. Queneau and M.-C. Scherrmann, New. J. Chem., 1994, 18, 279.
6. J. Mentech, I. Betremieux and B. Legger, Eur. Pat. Appl. EP 467,762 ( 1992); Chem. Abstr., 1992, 116, 256 232v; D. Jhurry, A. Deffieux, M. Fontanille, I. Betremieux, J. Mentech and G. Descotes, Makromol. Chem., 1992, 193, 2997.
7. S. Thévenet, G. Descotes, A. Bouchu and Y. Queneau, J. Carbohydr. Chem., 1997, 16, 691.
8. The polysubstituted sucrose octylcarbonates, when formed rapidly, tend to separate out of the reaction mixture, and often cover the glassware as well as the pH-stat electrode, preventing an accurate measure and control of the basic conditions.
9. Data for mono-O-octyloxycarbonyl sucrose derivatives. Elemental analysis for C₂₁H₃₈O₁₃·0.8H₂O: Calc.: C, 49.2; H, 7.8. Found: C, 49.1; H, 7.5%. δ_H(300 MHz,[²H₆]DMSO) 0.95 (t, 3 H, Me), 1.25 (m, 10 H, CH₂), 1.70 (m, 2 H, CH₂), 3.45 (s, 2 H, O-CH₂), 3.10–5.65 (m, 21 H, sucrose); v_max(KBr)/cm^–1999.9, 1047.8, 1266.8, 1401.9, 1748.8, 2855.0, 2926.7, 3341.1; m/z(M⁺+ NH₃) 516.
10. A. Lubineau, G. Bouchain and Y. Queneau, J. Chem. Soc., Perkin Trans. 1, 1995, 2433.