2-Carb-36

Continued from 2-Carb-35

Contents

• 2-Carb-36. Disaccharides
  • 36.1. Definition
  • 36.2. Disaccharides without a free hemiacetal group
  • 36.3. Disaccharides with a free hemiacetal group
  • 36.4. Trivial names
• Reference for this section

2-Carb-36.1. Definition

A disaccharide is a compound in which two monosaccharide units are joined by a glycosidic linkage.

2-Carb-36.2. Disaccharides without a free hemiacetal group

Disaccharides which can be regarded as formed by reaction of the two glycosidic (anomeric) hydroxy groups with one another are named, systematically, as glycosyl glycosides. The parent (cited as the 'glycoside' component) is chosen according to 2-Carb-2.1. Both anomeric descriptors must be included in the name.

Examples:

α-D-Glucopyranosyl α-D-glucopyranoside [α-D-Glcp-(11)-α-D-Glcp]
(trivial name α,α-trehalose)

β-D-Fructofuranosyl α-D-glucopyranoside [β-D-Fruf-(21)-α-D-Glcp]
not α-D-glucopyranosyl β-D-fructofuranoside
(trivial names sucrose, saccharose)

Note. Such disaccharides are also known as non-reducing disaccharides.

If derivatives are named on the basis of the trivial name, the component cited first in the systematic name receives primed locants.

Example:

4,6,6'-Trichloro-4,6,6'-trideoxygalactosucrose
or 6-chloro-6-deoxy-β-D-fructofuranosyl 4,6-dichloro-4,6-dideoxy-α-D-galactopyranoside
('galactosucrose' is a trivial name for the 4-epimer of sucrose)

2-Carb-36.3. Disaccharides with a free hemiacetal group

A disaccharide in which one glycosyl unit has replaced the hydrogen atom of an alcoholic hydroxy group of the other is named as a glycosylglycose. The locants of the glycosidic linkage and the anomeric descriptor(s) must be given in the full name.

There are two established methods in use for citing locants: either in parentheses between the glycosyl and glycose terms, or in front of the glycosyl prefix, as in the names of glycosides. The former (preferred) method is derived from that used to designate residues in oligosaccharides (see 2-Carb-37 and 2-Carb-38).

Note. The latter method is that used by Chemical Abstracts Service for disaccharides.

The O-locants used for the former method in the previous recommendations [1] are omitted here.

Examples:

α-D-Glucopyranosyl-(14)-β-D-glucopyranose [α-D-Glcp-(14)-β-D-Glcp]
or 4-O-α-D-glucopyranosyl-β-D-glucopyranose
(trivial name β-maltose, not β-D-maltose)

β-D-Galactopyranosyl-(14)-α-D-glucopyranose [β-D-Galp-(14)-α-D-Glcp]
or 4-O-β-D-galactopyranosyl-α-D-glucopyranose
(trivial name α-lactose, not α-D-lactose)

β-D-Galactopyranosyl-(14)-N-acetyl-D-glucosamine
(trivial name N-acetyllactosamine; LacNAc)

Note. Disaccharides with a free hemiacetal group are also known as reducing disaccharides.

2-Carb-36.4 Trivial names

Many of the naturally occurring disaccharides have well established trivial names. Some of these are listed below, together with the systematic names in both versions (see above).

Cellobiose	β-D-Glucopyranosyl-(14)-D-glucose
	4-O-β-D-Glucopyranosyl-D-glucose
Gentiobiose	β-D-Glucopyranosyl-(16)-D-glucose
	6-O-β-D-Glucopyranosyl-D-glucose
Isomaltose	α-D-Glucopyranosyl-(16)-D-glucose
	6-O-α-D-Glucopyranosyl-D-glucose
Melibiose	α-D-Galactopyranosyl-(16)-D-glucose
	6-O-α-D-Galactopyranosyl-D-glucose
Primeverose	β-D-Xylopyranosyl-(16)-D-glucose
	6-O-β-D-Xylopyranosyl-D-glucose
Rutinose	α-L-Rhamnopyranosyl-(16)-D-glucose
	6-O-α-L-Rhamnopyranosyl-D-glucose

The systematic names of trehalose, sucrose, maltose and lactose have been given already (with the formulae).

If derivatives are named on the basis of the trivial name, the component cited first in the systematic name receives primed locants.

Example:

1,2,2',3,3',4',6-Hepta-O-acetyl-6'-O-tosyl-α-cellobiose
or 2,3,4-tri-O-acetyl-6-O-tosyl-β-D-glucopyranosyl-(14)-1,2,3,6-tetra-O-acetyl-α-D-glucopyranose

If the reducing terminal is a uronic ester glycoside, the ester alkyl group is cited at the beginning of the name, and the aglyconic alkyl group is cited with the name of the glycosidic residue.

Example:

Methyl (3-O-acetyl-6-deoxy-2,4-di-O-methyl-α-L-galactpyranosyl)-(14)-(allyl 2,3-di-O-benzoyl-β-D-glucopyranosid)uronate

1. IUPAC Commission on the Nomenclature of Organic Chemistry (CNOC) and IUPAC-IUB Commission on Biochemical Nomenclature (CBN), Tentative rules for carbohydrate nomenclature, Part I, 1969, Biochem J., 125, 673-695 (1971); Biochemistry, 10, 3983-4004 (1971); Biochim. Biophys. Acta, 244, 223-302 (1971); Eur. J. Biochem., 21, 455-477 (1971) and 25, 4 (1972); J. Biol. Chem., 247, 613-635 (1972); ref.2, pp.127-148.

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