2-Carb-10

Continued from 2-Carb-8 and 2-Carb-9

Contents

• 2-Carb-10. Ketoses
  • 10.1. Classification
  • 10.2. Trivial names
  • 10.3. Systematic names
  • 10.4. Configurational prefixes

2-Carb-10.1. Classification

Ketoses are classified as 2-ketoses, 3-ketoses, etc., according to the position of the (potential) carbonyl group. The locant 2 may be omitted if no ambiguity can arise, especially in a biochemical context.

2-Carb-10.2. Trivial names

Ketoses with three to six carbon atoms are shown in Chart IV, with trivial names (and three-letter abbreviations) in parentheses. (See also the alphabetical listing of trivial names in the Appendix.)

Chart IV. Structures, with systematic and trivial names, of the 2-ketoses with three to six carbon atoms

The trivial names 'L-erythrulose' for D-glycero-tetrulose, 'L-ribulose' for D-erythro-pent-2-ulose, and 'L-xylulose' for D-threo-pent-2-ulose contain stereochemical redundancy and should not be used for naming derivatives. Sedoheptulose is the accepted trivial name for D-altro-hept-2-ulose.

2-Carb-10.3. Systematic names

The systematic names are formed from the stem name and the appropriate configurational prefix.

The stem names are formed from the corresponding aldose stem names (2-Carb-8.2) by replacing the ending '-ose' with '-ulose', preceded by the locant of the carbonyl group, e.g. hex-3-ulose. The chain is numbered so that the carbonyl group receives the lowest possible locant. If the carbonyl group is in the middle of a chain with an odd number of carbon atoms, a choice between alternative names is made according to 2-Carb-2.2.2>.

Note. In Chemical Abstracts Service (CAS) usage the locant for the carbonyl group precedes the stem name, e.g. 3-hexulose.

For examples see 2-Carb-10.4.

2-Carb-10.4. Configurational prefixes

For 2-ketoses, configurational prefixes are given in the same way as for aldoses (see 2-Carb-8.2 and 2-Carb-8.3).

Examples:

L-xylo-Hex-2-ulose
(L-Sorbose)

D-altro-Hept-2-ulose
(D-Sedoheptulose)

D-altro-Hept-2-ulopyranose

L-glycero-D-manno-Oct-2-ulose

For ketoses with the carbonyl group at C-3 or a higher-numbered carbon atom, the carbonyl group is ignored and the set of chiral centres is given the appropriate prefix or prefixes according to Chart I (cf. 2-Carb-8.4).

Examples:

D-arabino-Hex-3-ulose

D-xylo-Hex-3-ulose
not L-xylo-hex-4-ulose

L-gluco-Hept-4-ulose
not D-gulo-hept-4-ulose

L-threo-D-allo-Non-3-ulose

L-erythro-L-gluco-Non-5-ulose
not D-threo-L-allo-non-5-ulose

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