![]() They have a different configuration at the second carbon. Since D-Erythose and D-Threose are not mirror image of one another, they are diasteroisomers of one another. The two common types of aldotetroses are D-Erythose and D-Threose. An aldotetrose has an aldehyde functional group at carbon number one. Tetroses are monosaccharides with four carbon atoms. Glyceraldehydes are one of the smallest monosaccharides. They have a single asymmetric carbon atom: D- and L-glyceraldehyde are enantiomers of one another. Trioses are monosacchrides with three carbon atoms aldotrioses have an aldehyde functional group at carbon number one. List of common aldoses Gyceraldehyde Triose See Chirality for the naming using D/L system. ![]() We usually focus on the D sugars since they are more frequently in natural existence, while the L sugars, diastereomer of the D sugars, are less common. Following the same calculation, we know that aldotetroses have four stereoisomers, aldopentoses have eight stereoisomers, and aldohexoses have sixteen stereoisomers. For example, aldotriose has three carbons( C), one stereocenter( n) - it has two stereoisomers. Again, n is the number of stereocenter(s). We can also use the formula 2 n to calculate the maximum number of stereoisomers that are possible to exist in a molecule. Each sugar has n = C - 2 numbers chiral center(s), where C is the number of carbons. Furthermore, for example, the simplest sugar with three carbons - glyceraldehyde (containing an aldehyde group), and sugar with seven carbons - L-glycero- D-manno-heptose, can be found in this category. Aldoses are distinguishable by the carbonyl(C=O) group located at the end of the carbon chain, which differs from ketose, which has the carbonyl group in the middle of the carbon chain. The L and D symbols apply to the two different configurations of the asymmetric carbon farthest from the aldehyde group. The two simplest forms of Aldoses are L- and D-Glyceraldehydes, which are three-carbon structures that each contain one aldehyde and two hydroxyl groups. An Aldose is a type of monosaccharide, which is a chiral molecule that plays a key role in the development of nucleic acids. The area marked blue indicate the differing stereogenic center Simple Aldoses Īn Aldose' contains an aldehyde with two or more hydroxyl groups attached one of the hydroxyl groups is at end opposite to the aldehyde. As shown in the figure below, D-Glucose and D-Mannose are an example of an epimer. Epimers are two diastereomers that differ only at one stereocenter. Lastly, another type of isomer that carhbohydrates that can take on are epimers. An example of two carbohydrates that are diastereoisomers are D-Glucose and D-Altrose as seen in the figure to the left. ![]() Unlike an enantiomer, diastereomers are NOT object and mirror image. Carbohydrates are classified as diastereomers if their chiral carbons are connected to the exactly the same substrates but connected at differing configurations (R or S). An example of an enantiomer is the D and L isomers of glucose, as shown by the figure to the right.Ī second type of isomer seen in carbohydrates are diastereoisomers. Two carbohydrates are said to be enantiomers if they are nonsuperimposable mirror images of one another. The blue indicates the D-isomer and the red indicates the L-isomerĭue to the fact that carbohydrates contain multiple stereocenters, many isomers are possible including enantiomers, diastereoisomers, and epimers. The areas marked blue indicate the differing stereogenic centers. On the Fischer projection, if the farthest hydroxyl(-OH) group is on the right, then it is classified as D sugar, if the hydroxyl group is on the left, then it is a L sugar.Įnantiomers, Diastereoisomers(anomerism), and Epimers Example of Diastereomers. The L and D confirmations represent the absolute configuration of the asymmetric carbon farthest away from the ketone or aldehyde group on the monosaccharide. Monosaccharides are often represented by a Fischer Projection, a shorthand notation particularly useful for showing stereochemistry in straight chained organic compounds. Monosaccharides may be further classified based on the number of carbon atoms in the backbone, which can be designated with the prefixes tri-(3), tetr-(4), pent-(5), hex-(6), hept-(7), etc. A ketose signifies that the sugar contains a ketone functional group. The sugar is an aldose if it contains an aldehyde functional group. Monosaccharides are the simplest form of carbohydrates and may be subcategorized as aldoses or ketoses. ![]()
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