carbohydrate chemistry
A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ma ...
carbohydrate acetalisation is an
organic reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, mechanistic organ ...
and a very effective means of providing a
protecting group
A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis.
In man ...
. The example below depicts the acetalisation reaction of D-
ribose
Ribose is a simple sugar and carbohydrate with molecular formula C5H10O5 and the linear-form composition H−(C=O)−(CHOH)4−H. The naturally occurring form, , is a component of the ribonucleotides from which RNA is built, and so this comp ...
1. With
acetone
Acetone (2-propanone or dimethyl ketone) is an organic compound with the chemical formula, formula . It is the simplest and smallest ketone (). It is a colorless, highly Volatile organic compound, volatile, and flammable liquid with a charact ...
pentose
In chemistry, a pentose is a monosaccharide (simple sugar) with five carbon atoms. The chemical formula of many pentoses is , and their molecular weight is 150.13 g/mol.centerKinetic reaction control results from 2-methoxypropene as the reagent. D-ribose in itself is a
hemiacetal
In organic chemistry, a hemiacetal is a functional group the general formula , where is a hydrogen atom or an organic substituent. They generally result from the nucleophilic Addition reaction, addition of an Alcohol (chemistry), alcohol (a compo ...
and in equilibrium with the
pyranose
In organic chemistry, pyranose is a collective term for saccharides that have a chemical structure that includes a six-membered ring consisting of five carbon atoms and one oxygen atom (a heterocycle). There may be other carbons external to the ...
3. In aqueous solution ribose is 75% pyranose and 25%
furanose
A furanose is a collective term for carbohydrates that have a chemical structure that includes a five-membered ring system consisting of four carbon atoms and one oxygen atom. The name derives from its similarity to the oxygen heterocycle furan, ...
and a different acetal 4 is formed.
Selective acetalization of carbohydrate and formation of acetals possessing atypical properties is achieved by using arylsulfonyl acetals. An example of arylsulfonyl acetals as carbohydrate-protective groups are phenylsulfonylethylidene acetals. These acetals are resistant to the acid hydrolysis and can be deprotected easily by classical reductive conditions.
References
* ''Preparative Carbohydrate Chemistry'' Calinaud, P.; Gelas, J. in . Hanessian, S. Ed. Marcel Dekker, Inc.: New York, 1997.