Continued from 2-Carb-32
Glycosides were originally defined as mixed acetals (ketals) derived from cyclic forms of monosaccharides.
However, the term 'glycoside' was later extended to cover not only compounds in which, as above, the anomeric hydroxy group is replaced by a group -OR, but also those in which the replacing group is -SR (thioglycosides), -SeR (selenoglycosides), -NR1R2 (N-glycosides), or even -CR1R2R3 (C-glycosides). 'Thioglycoside' and 'selenoglycoside' are legitimate generic terms; however the use of 'N-glycoside', although widespread in biochemical literature, is improper and not recommended here ('glycosylamine' is a perfectly acceptable term). 'C-Glycoside' is even less acceptable (see Note to 2-Carb-33.7). A glossary of terms based on 'glycose' is given in the Appendix.
Particularly in naturally occurring glycosides, the compound ROH from which the carbohydrate residue has been removed is often termed the aglycone, and the carbohydrate residue itself is sometimes referred to as the 'glycone'.
Note. The spelling 'aglycon' is often encountered.
Glycosides can be named in three different ways:
(a) By replacing the terminal '-e' of the name of the corresponding cyclic form of the monosaccharide by '-ide' and preceding this, as a separate word (the intervening space is significant), the name of the group R (see examples below).
Note. This is the 'classical' way of naming glycosides. It is used mainly when the group R is relatively simple (e.g. methyl, ethyl, phenyl).
(b) By using the term 'glycosyloxy-', in the appropriate form for the monosaccharide, as prefix, for the name of the compound.
Note. This prefix includes the oxygen of the glycosidic bond. An example is given in 2-Carb-31.2; more are given below.
(c) By using the term 'O-glycosyl-' as prefix to the name of the hydroxy compound.
Note. This prefix does not include the oxygen of the glycosidic group. This is the appropriate method for naming natural products if the trivial name includes the OH group. The system is also used to name oligosaccharides (see 2-Carb-37).
Note. A common biochemical practice would give the name (20S)-3α-(β-D-glucopyranuronosyloxy)-5β-pregnan-20-ol. This practice of naming glycosyl residues from uronic acids as 'glycuronosyl' is unsatisfactory because it implies the acceptance of the parent name 'glycuronose'. However the use of a two-word substituent prefix (glycosyloxyuronic acid), ending with a functional class name, remains inherently problematic, since it contravenes general organic nomenclature principles [13,14]. The latter practice has the advantage of retaining homomorphic relationships between glycoses and glycuronic acids.
trivial name sambunigrin
7-(β-D-Glucopyranosyloxy)-8-hydroxycoumarin; trivial name daphnin
Glycosides can be named as substituents by the methods of 2-Carb-31.
Names for individual compounds can be formed, like those for glycosides, in three ways, as follows.
(a) By using the term thioglycoside, preceded by the name of the group R.
(b) With the prefix 'glycosylthio-', followed by the name of the compound RH; this prefix includes the sulfur atom.
(c) With the prefix 'S-glycosyl-' (not including the S atom), followed by the name of the thio compound.
Sulfoxides and sulfones can also be named by functional class nomenclature [13, 14].
or 4-carboxyphenyl 1-thio-α-D-ribofuranoside
S-β-D-Glucopyranosyl (Z)-O-(potassium sulfonato)but-3-enehydroximothioate
(trivial name sinigrin)
Phenyl tetra-O-acetyl-α-D-glucopyranosyl sulfoxide
or phenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-D-glucopyranoside S-oxide
Names are formed analogously to those for thioglycosides (2-Carb-33.3).
or (S)-2-amino-2-carboxyethyl 1-seleno-β-D-ribopyranoside
2-Carb-33.5. Glycosyl halides
Compounds in which the anomeric hydroxy group is replaced by a halogen atom are named as glycosyl halides. Pseudohalides (azides, thiocyanates etc.) are named similarly.
Methyl (2,3,4-tri-O-acetyl-α-D-glucopyranosyl)uronate bromide
not methyl 2,3,4-tri-O-acetyl-1-bromo-1-deoxy-α-D-glucopyranuronate
or 3,4,5-tri-O-benzyl-aldehydo-α-D-arabino-hexos-2-ulopyranosyl bromide
Methyl (5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-α-D-galacto-non-2-ulopyranosyl)onate chloride
2-Carb-33.6. N-Glycosyl compounds (glycosylamines)
N-Glycosyl derivatives are conveniently named as glycosylamines. In the case of complex heterocyclic amines, such as nucleosides, the same approach is used.
(trivial name uridine)
[trivial name N1-(N-acetylglucosaminyl)-L-lysinamide]
(trivial name β-N-acetylglucosaminyl-L-asparagine)
2-Carb-33.7. C-Glycosyl compounds
Compounds arising formally from the elimination of water from the glycosidic hydroxy group and an H atom bound to a carbon atom (thus creating a C-C bond) are named using the appropriate 'glycosyl-' prefixes (or other methods as appropriate, avoiding 'C-glycoside' terminology).
Note. The term C-glycoside, introduced for naming pseudouridine (a nucleoside from transfer RNA), is a misnomer. All other glycosides are hydrolysable; the C-C bond of 'C-glycosides' is usually not. The use and propagation of names based on 'C-glycoside' terminology is therefore strongly discouraged.
not adenine 8-(2-deoxyriboside)
5-β-D-Ribofuranosyluracil; trivial name pseudouridine
not cyanomethyl C-β-D-glucopyranoside
2-β-D-Glucopyranosyl-1,3,6,7-tetrahydroxyxanthen-9-one; trivial name mangiferin
9(10H)-one; trivial names aloin A, (10S)-barbaloin
trivial name violanthin
13. IUPAC Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F and H, 1979 Edition, Pergamon Press, Oxford, U.K. Sections E and F are reprinted in ref. 2, pp. 1-18 and 19-26, respectively.
14. Guide to IUPAC Nomenclature of Organic Compounds, Recommendations 1993, Blackwell Scientific Publications, Oxford (1993).
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