Synthesis of methyl ether derivatives of sucrose

A practical synthesis of capped 4-methylumbelliferyl hyaluronan disaccharides and tetrasaccharides as potential hyaluronidase substrates

The synthesis of hyaluronan dimers and tetramers equipped with a 4-methylumbelliferyl group at the reducing end to potentially allow monitoring of hyaluronidase activities is described. The 4-OH at the non-reducing glucuronate in the presented series is either removed or methylated to prohibit transglycosylase reactions, leading to a total of four probes.

Synthesis of 1',6'-disubstituted sucroses and their behavior as glucosyl donors for a microbial alpha-glucosyltransferase

Versatile 6'-chloro-6'-deoxy-1'-substituted sucrose derivatives were synthesized in search of an optimum donor substrate for the intermolecular transglucosylation with the alpha-glucosyltransferase from Protaminobacter rubrum. Two substituents at the C-1' and C-6' positions of sucrose were introduced utilizing the distinct reactivity of the corresponding sulfonates. Methyl beta-D-arabinofuranoside was most efficiently glucosylated with the 1'-deoxy derivative 5. Hydroxyl and fluoro groups at C-1' show a tendency to enhance the intramolecular transglucosylations, giving 3-O-(alpha-D-glucopyranosyl)-D-fructose derivatives.

Cyclic acetals of 4,1',6'-trichloro-4,1',6'-trideoxy-galacto-sucrose and their conversion into methyl ether derivatives

The acid-catalysed reaction of 4,1',6'-trichloro-4,1',6'-trideoxy-galacto- sucrose (1) with 5.5 equiv. of 2-methoxypropene in N,N-dimethylformamide followed by acetylation gave 3',4'-di-O-acetyl-4,1',6'-trichloro-4,1',6'-trideoxy-2,3-O- isopropylidene-6-O-(1-methoxy-1-methylethyl)-galacto-sucrose (2, 2%), 6,3',4'- tri- O-acetyl-4,1',6'-trichloro-4,1',6'-trideoxy-2,3-O-isopropylidene-galacto -sucrose (3, 31%), 3',4'-di-O-acetyl-4,1',6'-trichloro-4,1',6'-trideoxy-2,3-O- isopropylidene- galacto-sucrose (4, 38%), 3'-O-acetyl-4,1',6'-trichloro-4,1',6'-trideoxy-2,3-O- isopropylidene- galacto-sucrose (5, 13%), and 2,3',4'-tri-O-acetyl-4,1',6'-trichloro- 4,1',6'-trideoxy-galacto-sucrose (6, 13%). Methylation of 4 followed by removal of the protecting groups gave 4,1',6'-trichloro-4,1',6'-trideoxy-6-O-methyl- galacto- sucrose (8). 4,1',6'-Trichloro-4,1',6'-trideoxy-3-O-methyl-galacto-sucrose (11) was synthesised from 6 by preferential tert-butyldiphenylsilylation of HO-6 followed by methylation and removal of the protecting groups. Likewise, 4,1',6'-trichloro- 4,1',6'-trideoxy-4'-O-methyl-galacto-sucrose (14) was synthesised from 5. Treatment of 3 with aqueous acetic acid followed by methylation and removal of the protecting groups afforded 4,1',6'-trichloro-4,1'6'-trideoxy-2,3-di-O-methyl- galacto-sucrose (17).

Structural relationships of sugars to taste

Chemical modification of sugars and their simple analogues indicates that these types of compound are almost always sweet, bitter, or bitter/sweet; hence, the two basic tastes may be intimately associated features of the same molecule. Stepwise modification at each chiral center around the sugar ring allows the sapid functions in these molecules to be mapped and leads to the inescapable conclusion that sugar molecules may be "polarized" on taste bud receptors, so that one end of the molecule elicits sweetness and the other bitterness. However, more extensive chemical modification evidently causes the molecule to realign itself in entirely different ways on the receptor. In most oligosaccharides only one sugar residue is likely to bind to the taste receptor, and this is probably a nonreducing end group, because the anomeric center of glucopyranose types of structure does not appear to affect sweetness. Sweetness depresses bitterness and bitterness depresses sweetness. Hence, it is not possible to make structural comparisons between analogues without correcting for these effects. However, some semiquantitative studies have established the value of current hydrogen bond theories of sweetness and the ideal oxygen-oxygen interorbital spacings for sweetness criteria in sugar molecules.