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Author: Subject: Saccharides convertions?
kazaa81
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smile.gif posted on 30-10-2004 at 15:17
Saccharides convertions?


Hallo to all,
I'm searching for procedure(s) which allow
to convert one saccharides to another one, example sorbitol from glucose, or from saccharose, etc.

Any info. about synthesis is welcomed!

Thanx for help.
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JohnWW
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[*] posted on 30-10-2004 at 19:08


If you could do it, you could make a huge fortune, from converting sucrose (or its glucose + fructose components) to sugars which cannot be metabolized by the bacteria which cause dental decay, particularly xylitol, and I think also sorbitol. You would also be able to convert sucrose/glucose/fructose to rarer and more expensive sugars which are important in chemical analysis or biochemical research, e.g. mannitol, mannose, ribose, allose, ribulose, tagatose, arabinoselyxose, talose, gulose, altrose, idose, etc., and their optical isomers.

Unfortunately, only a few simple interconversions can be done, usually involving oxidations and reductions, and hydrolysis of polysaccharides, rather than changes of their chiral configurations. Some sugars may be synthesized from smaller molecules, but usually as a mixture of optical isomers.

[Edited on 31-10-2004 by JohnWW]
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unionised
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[*] posted on 31-10-2004 at 03:01


The reduction of glucose to sorbitol is an industrial process, they use hydrogenation or electrolysis. I guess that, on the home-made scale, it might be a bit fiddly. Perhaps the biggest problem would be to separate the products.
Unfortunately, this means that someone has beaten you to the "huge fortune" that John mentions.
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chemoleo
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[*] posted on 31-10-2004 at 14:24


Yes, most of the times the reduction would entail the removal of the ring structure, i.e. by reducing the keto or aldehyde to alcohol, like unionised mentions.
This is a specific case, however. Sugars mainly differ not by the presence or absence of a carbonyl, but by the stereochemical position of the hydroxyls (and of course by the linkage of different sugars to form polysaccharides). Conversion of a particular chiral OH to the other form is very tricky, and normally either entails the formation of a keto-derivative, which is then reduced agaiin to the hydroxyl, which is not always possible due to ring constraints. Enzymes are very good at this, by sterically favouring one chiral form over the other.
However, as you guys are saying above, definitely not something that can be easily done. Far simpler to have a specific fungus/bacterium producing masses of a particular sugar, or isolating it from generic sugar extracts by fractional crystallisation etc.

[Edited on 31-10-2004 by chemoleo]




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