Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/16447
Title: Intensely sweet halodeoxy analogues of sucrose: Synthesis and structure-sweetness relationship
Authors: MUHAMMAD SOFIAN BIN ASI SIHOMBING
Keywords: sucrose, halodeoxy sucrose, sweetness, stereochemistry, molecular dynamics, AH,B,γ-glucophore.
Issue Date: 4-Mar-2004
Source: MUHAMMAD SOFIAN BIN ASI SIHOMBING (2004-03-04). Intensely sweet halodeoxy analogues of sucrose: Synthesis and structure-sweetness relationship. ScholarBank@NUS Repository.
Abstract: A series of 4-halo-4-deoxy, 4,1a??,6a??-trihalo-4,1a??,6a??-trideoxy and 4,1a??,4a??,6a??-tetrahalo-4,1a??,4a??,6a??-tetradeoxy sucrose analogues were synthesized to study the effects of halogen(s) on the sweet taste of sucrose. The key intermediate in the syntheses of 4-halo-4-deoxy and 4,1a??,6a??-trihalo-4,1a??,6a??-trideoxy sucrose analogues is 3,4-di-O-acetyl-1,6-di-O-trityl-I?-D-fructofuranosyl 2,3,6-tri-O-acetyl-I?-D-galactopyranoside, which then underwent halogenation to introduce the desired halogen substituent at C-4. The subtle differences in reactivity of C-1a?? and C-6a?? trifluoromethanesulfonates enabled the introduction of different halogen substituents at C-1a?? and C-6a??. The C-4a?? halodeoxy fructofuranosyl analogues were obtained by regioselective epoxide ring-opening of 3,4-anhydro-1,6-di-O-trityl-I?-D-lyxo-hexulofuranosyl 2,3,4-tri-O-acetyl-6-O-trityl-I?-D-glucopyranoside. The C-4a?? halodeoxy tagatofuranosyl analogues, on the other hand, were obtained by nucleophilic displacement of a C-4a?? trifluoromethanesulfonate, which was formed regioselectively via a stannylene acetal derivative of 1,6-di-O-trityl-I?-D-fructofuranosyl 6-O-trityl-I?-D-glucopyranoside. These C-4a?? halodeoxy analogues were eventually converted into the corresponding 4,1a??,4a??,6a??-tetrahalogenated sucrose derivatives. The sweetness intensities of the halodeoxy sucrose analogues were assessed using a taste panel. The 4-halo-4-deoxy sucrose derivatives possess little or no sweetness, but the sweetness intensities of 4,1a??,6a??-trihalo-4,1a??,6a??-trideoxy and 4,1a??,4a??,6a??-tetrahalo-4,1a??,4a??,6a??-tetradeoxy sucrose derivatives fall between 130 to 370 times that of sucrose. The tetrahalodeoxy tagatofuranosyl galactopyranoside analogues, however, are bitter. These results showed the importance of C-4 and C-4a?? halogens in enhancing the intensity of sweetness, and that they are likely to be the I?-sites in Shallenberger-Acree-Kier AH,B,I?-glucophore. The stereochemistry at these positions is also critical for sweetness. Molecular dynamics simulations were also undertaken to probe the conformational behaviour of sucrose and its halodeoxy analogues in water. Semi-empirical methods were used to determine the low-energy conformers, which then serve as starting structures for the molecular dynamics study. The interatomic distances, particularly those involving O-2, O-3, O-3a??, C-4-halogen and C-4a??-halogen, were also determined. Based on the modeling studies and sweetness data, it appears that there are four possible AH,B,I?-glucophores. Of these, the ones which include C-4-halogen (galacto) as the I?-site are most likely to be the major glucophore.
URI: http://scholarbank.nus.edu.sg/handle/10635/16447
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Summary.pdf96.96 kBAdobe PDF

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