Monosaccharide nomenclature is the naming system of the building blocks of carbohydrates, the

monosaccharide Monosaccharides (from Greek '' monos'': single, '' sacchar'': sugar), also called simple sugars, are the simplest forms of sugar and the most basic units (monomers) from which all carbohydrates are built. They are usually colorless, water-solu ...

s, which may be monomers or part of a larger

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and ...

. Monosaccharides are subunits that cannot be further hydrolysed in to simpler units. Depending on the number of carbon atom they are further classified into

trioses A triose is a monosaccharide, or simple sugar, containing three carbon atoms. There are only three possible trioses (including dihydroxyacetone): L-glyceraldehyde and D-glyceraldehyde, the two enantiomers of glyceraldehyde, which are aldotrioses ...

, tetroses, pentoses,

hexoses In chemistry, a hexose is a monosaccharide (simple sugar) with six carbon atoms. The chemical formula for all hexoses is C6H12O6, and their molecular weight is 180.156 g/mol. Hexoses exist in two forms, open-chain or cyclic, that easily convert ...

etc., which is further classified in to

aldoses An aldose is a monosaccharide (a simple sugar) with a carbon backbone chain with a carbonyl group on the endmost carbon atom, making it an aldehyde, and hydroxyl groups connected to all the other carbon atoms. Aldoses can be distinguished from keto ...

and

ketoses A ketose is a monosaccharide containing one ketone group per molecule. The simplest ketose is dihydroxyacetone, which has only three carbon atoms. It is the only ketose with no optical activity. All monosaccharide ketoses are reducing sugars, be ...

depending on the type of

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the res ...

present in them.

Systematic name of molecular graph

The elementary formula of a simple monosaccharide is C_''n''H_2''n''O_''n'', where the integer ''n'' is at least 3 and rarely greater than 7. Simple monosaccharides may be named generically based on the number of carbon atoms ''n'':

, tetroses, pentoses,

, etc. Every simple monosaccharide has an acyclic (open chain) form, which can be written as H-(CH(OH))_\mathit-(C=O)-(CH(OH))_\mathit-H; that is, a straight chain of carbon atoms, one of which is a

carbonyl In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a ...

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic ide ...

, all the others bearing a hydrogen -H and a

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy g ...

-OH each, with one extra hydrogen at either end. The carbons of the chain are conventionally numbered from 1 to ''n'', starting from the end which is closest to the carbonyl. If the carbonyl is at the very beginning of the chain (carbon 1), the monosaccharide is said to be an

aldose An aldose is a monosaccharide (a simple sugar) with a carbon backbone chain with a carbonyl group on the endmost carbon atom, making it an aldehyde, and hydroxyl groups connected to all the other carbon atoms. Aldoses can be distinguished from ket ...

, otherwise it is a

ketose A ketose is a monosaccharide containing one ketone group per molecule. The simplest ketose is dihydroxyacetone, which has only three carbon atoms. It is the only ketose with no optical activity. All monosaccharide ketoses are reducing sugars, be ...

. These names can be combined with the chain length prefix, as in

aldohexose In chemistry, a hexose is a monosaccharide (simple sugar) with six carbon atoms. The chemical formula for all hexoses is C6H12O6, and their molecular weight is 180.156 g/mol. Hexoses exist in two forms, open-chain or cyclic, that easily conver ...

ketopentose 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.3-ketopentose means H(CHOH)₂(C=O)(CHOH)₂H. An alternative nomenclature uses the suffix '-ose' only for aldoses, and '-ulose' for ketoses. The position of the carbonyl (when it is not 1 or 2) is indicated by a numerical infix. For example, hexose in this nomenclature means H(C=O)(CHOH)₅H, pentulose means H(CHOH)(C=O)(CHOH)₃H, and hexa-3-ulose means H(CHOH)₂(C=O)(CHOH)₃H.

Naming of acyclic stereoisomers

Open-chain monosaccharides with same molecular graph may exist as two or more

stereoisomers In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in ...

. The

Fischer projection In chemistry, the Fischer projection, devised by Emil Fischer in 1891, is a two-dimensional representation of a three-dimensional organic molecule by projection. Fischer projections were originally proposed for the depiction of carbohydrates ...

is a systematic way of drawing the

skeletal formula The skeletal formula, or line-angle formula or shorthand formula, of an organic compound is a type of molecular structural formula that serves as a shorthand representation of a molecule's bonding and some details of its molecular geometry. A ...

of an open-chain monosaccharide so that each stereoisomer is uniquely identified. Two isomers whose molecules are mirror-images of each other are identified by prefixes '-' or '-', according to the handedness of the chiral carbon atom that is farthest from the carbonyl. In the Fischer projection, that is the second carbon from the bottom; the prefix is '-' or '-' according to whether the hydroxyl on that carbon lies to the right or left of the backbone, respectively. If the molecular graph is symmetrical (H(CHOH)(CO)(CHOH)H) and the two halves are mirror images of each other, then the molecule is identical to its mirror image, and there is no '-' form. A distinct common name, such as "glucose" or "ribose", is traditionally assigned to each pair of mirror-image stereoisomers, and to each achiral stereoisomer. These names have standard three-letter abbreviations, such as 'Glc' for glucose and 'Rib' for ribose. Another nomenclature uses the systematic name of the molecular graph, a '-' or '-' prefix to indicate the position of the last chiral hydroxyl on the Fischer diagram (as above), and another italic prefix to indicate the positions of the remaining hydroxyls relative to the first one, read from bottom to top in the diagram, skipping the keto group if any. These prefixes are attached to the systematic name of the molecular graph. So for example, -glucose is -''gluco''-hexose, -ribose is -''ribo''-pentose, and -psicose is -''ribo''-hexulose. Note that, in this nomenclature, mirror-image isomers differ only in the ''/'' prefix, even though all their hydroxyls are reversed. acyclic sugars

The following tables shows the Fischer projections of selected monosaccharides (in open-chain form), with their conventional names. The table shows all aldoses with 3 to 6 carbon atoms, and a few ketoses. For chiral molecules, only the '-' form (with the next-to-last hydroxyl on the right side) is shown; the corresponding forms have mirror-image structures. Some of these monosaccharides are only synthetically prepared in the laboratory and not found in nature.

Names of aldoses

Names of ketoses

Names of 3-ketoses

Cyclic forms

For

s in their cyclic form, an infix is placed before the '-ose', '-ulose', or n''-ulose' suffix to specify the ring size. The infix is "furan" for a 5-atom ring, "pyran" for 6, "septan" for 7, and so on. Ring closure creates another chiral center at the

anomeric carbon In carbohydrate chemistry, a pair of anomers () is a pair of near-identical stereoisomers that differ at only the anomeric carbon, the carbon that bears the aldehyde or ketone functional group in the sugar's open-chain form. However, in order fo ...

(the one with the

hemiacetal A hemiacetal or a hemiketal has the general formula R1R2C(OH)OR, where R1 or R2 is hydrogen or an organic substituent. They generally result from the addition of an alcohol to an aldehyde or a ketone, although the latter are sometimes called hemik ...

acetal In organic chemistry, an acetal is a functional group with the connectivity . Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments n ...

functionality), and therefore each open-chain stereoisomer gives rise to two distinct stereoisomers (

anomer In carbohydrate chemistry, a pair of anomers () is a pair of near-identical stereoisomers that differ at only the anomeric carbon, the carbon that bears the aldehyde or ketone functional group in the sugar's open-chain form. However, in order fo ...

s). These are identified by the prefixes 'α-' and 'β-', which denote the relative configuration of the anomeric carbon to that of the stereocenter at the other end of the carbon chain. If the conformation (R or S) is identical at both the anomeric carbon and the most distant stereocenter, the configuration is 'α-'. If the conformations are different, the configuration is 'β-'Essentials of Glycobiology
/ref> Examples cyclic sugars

Glycosides

Glycosides In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...

are

saccharide In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...

s in which the hydroxyl -OH at the

anomeric In carbohydrate chemistry, a pair of anomers () is a pair of near-identical stereoisomers that differ at only the anomeric carbon, the carbon that bears the aldehyde or ketone functional group in the sugar's open-chain form. However, in order f ...

centre is replaced by an oxygen-bridged group -OR. The carbohydrate part of the molecule is called glycone, the -O- bridge is the glycosisdic oxygen, and the attached group is the aglycone. Glycosides are named by giving the aglyconic

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

HOR, followed by the saccharide name with the '-e' ending replaced by '-ide'; as in phenol D-glucopyranoside. glycoside

Modified sugars

Modification of sugar is generally done by replacing one or more –OH group with other functional groups at all positions except C-1. Rules for nomenclature of modified sugars: * State if the sugar is a

deoxy sugar Deoxy sugars are sugars that have had a hydroxyl group replaced with a hydrogen atom. Examples include: * Deoxyribose, or 2-deoxy-D-ribose, a constituent of DNA * Fucose, or 6-deoxy-L-galactose, main component of fucoidan of brown algae, and pr ...

, which means the –OH group is replaced by H. * Specify the position of

deoxygenation Deoxygenation is a chemical reaction involving the removal of oxygen atoms from a molecule. The term also refers to the removal of molecular oxygen (O2) from gases and solvents, a step in air-free technique and gas purifiers. As applied to orga ...

. * If there is a substituent other than H in the place of –OH, specify what it is. * Specify the relative configuration of all stereogenic centres (manno, gluco etc.). * Specify the ring size (furanose, pyranose etc.) and anomeric configuration ( a or b). * State the chain length only in situation where –OH is replaced with H. * Alphabetize all the substituent groups (deoxy, -iodo, -amino etc.). Di-, tri- etc. prefixes do not count. Examples modified sugar

Protected sugars

Sugars in which –OH is protected by some modification are called protected sugars. Rules for nomenclature for protected sugars: * Specify the number of particular

protecting groups 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 ...

(di, tri, tetra etc.). * List groups alphabetically along with all other substituents ( di, tri prefixes do not count). protected

References

{{Carbohydrates Chemical nomenclature Carbohydrates Carbohydrate chemistry