2-Carb-16

Continued from 2-Carb-14 and 2-Carb-15

Contents

• 2-Carb-16. Other substituted monosaccharides
  • 16.1. Replacement of hydrogen at a non-terminal carbon atom
  • 16.2. Replacement of OH at a non-terminal carbon atom
  • 16.3. Unequal substitution at a non-terminal carbon atom
  • 16.4. Terminal substitution
  • 16.5. Replacement of carbonyl oxygen by nitrogen (imines, hydrazones, osazones etc.)
  • 16.6. Isotopic substitution and isotopic labelling
• Reference for this section

2-Carb-16.1. Replacement of hydrogen at a non-terminal carbon atom.

The compound is named as a C-substituted monosaccharide. The group having priority according to the Sequence Rule ([13], Section E) is regarded as equivalent to OH for assignment of configuration. Any potential ambiguity (particularly when substitution is at the carbon atom where ring formation occurs) should be avoided by use of the R,S system to specify the modified stereocentre.

Examples:

2-C-Phenyl-α-D-glucopyranose

2-C-Acetamido-2,3,4,6-tetra-O-acetyl-α-D-mannopyranosyl fluoride

(5R)-1,2,3,4-Tetra-O-acetyl-5-bromo-α-D-xylo-hexopyranuronic acid
or 1,2,3,4-tetra-O-acetyl-5-bromo-β-L-idopyranuronic acid

2-Carb-16.2. Replacement of OH at a non-terminal, non-anomeric carbon atom

The compound is named as a substituted derivative of a deoxy sugar. The group replacing OH determines the configurational description. Any potential ambiguity should be dealt with by the alternative use of the R,S system to specify the modified stereocentre.

Examples:

2-Deoxy-2-phenyl-α-D-glucopyranose or 2-deoxy-2-C-phenyl-α-D-glucopyranose
or (2R)-2-deoxy-2-phenyl-α-D-arabino-hexopyranose

2,3-Diazido-4-O-benzoyl-6-bromo-2,3,6-trideoxy-α-D-mannopyranosyl nitrate

Note. Use of the symbol C- is essential only in cases of potential ambiguity, to make clear that substitution is at carbon rather than at a heteroatom (cf. 2-Carb-18.2); however, it may also be used for emphasis.

2-Carb-16.3. Unequal substitution at a non-terminal carbon atom

The compound is named as a disubstituted deoxy sugar. Configuration is determined by regarding the substituent having priority according to the Sequence Rule ([13], Section E), as equivalent to OH. Any potential ambiguity should be dealt with by the alternative use of the R,S system to specify the modified stereocentre.

Example:

(2R)-2-Bromo-2-chloro-2-deoxy-α-D-arabino-hexopyranose
or 2-bromo-2-chloro-2-deoxy-α-D-glucopyranose
(Br has priority over Cl)

2-Carb-16.4. Terminal substitution

If substitution at the terminal carbon atom of the carbohydrate chain creates a chiral centre, the stereochemistry is indicated by the R,S system.

Example:

(5R)-5-C-Cyclohexyl-5-C-phenyl-D-xylose

Note. A monosaccharide with a terminal methyl group is named as a deoxy sugar, not as a C-methyl derivative.

Substitution of aldehydic H by a ring or ring system is indicated simply with a C-substituent prefix.

Examples:

1-C-Phenyl-D-glucose
not 1-C-phenyl-D-gluco-hex-1-ulose

1-C-Phenyl-β-D-glucopyranose

2-Carb-16.5. Replacement of carbonyl oxygen by nitrogen (imines, oximes, hydrazones, osazones etc.)

The imino analogue of a monosaccharide may be named as an imino-substituted deoxy alditol.

Example:

1-Deoxy-1-(methylimino)-D-xylitol

Oximes, hydrazones and analogues are named directly as oxime or hydrazone derivatives etc.

Example:

D-Glucose phenylhydrazone

The vicinal dihydrazones formed from monosaccharides with arylhydrazines have been called arylosazones, but are preferably named as ketoaldose bis(phenylhydrazone)s

Example:

D-arabino-Hexos-2-ulose bis(phenylhydrazone)
or D-arabino-hex-2-ulose phenylosazone

The triazoles formed on oxidising arylosazones (commonly called osotriazoles) may also be named as triazolylalditols.

D-arabino-Hexos-2-ulose phenylosotriazole
or (1R)-1-(2-phenyl-2H-1,2,3-triazol-4-yl)-D-erythritol
or 2-phenyl-4-(L-arabino-1,2,3,4-tetrahydroxybutyl)-2H-1,2,3-triazole

2-Carb-16.6. Isotopic substitution and isotopic labelling

Rules for designating isotopic substitution and labelling are given in [13] (Section H). Parentheses indicate substitution; square brackets indicate labelling. The locant U indicates uniform labelling.

Examples:

When isotopic substitution creates a centre of chirality, configuration is defined as for other types of substitution (see 2-Carb-16.1 to 2-Carb-16.4).

Example:

2-Deoxy-D-(2-²H)lyxose (substituted) or (2S)-2-deoxy-D-threo-(2-²H)pentose

2-Deoxy-2-[¹⁸F]fluoro-D-glucopyranose (labelled)
or (2R)-2-deoxy-2-[¹⁸F]fluoro-D-arabino-hexopyranose

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.

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