Continued from 2-Carb-16
Contents
Note This is based on the 1980 recommendations [5]. Some examples have been omitted.
2-Carb-17.1. General principles
This section relates to the introduction of a double or triple bond between two contiguous carbon atoms of the backbone chain of a monosaccharide derivative. A double bond between a carbon atom of the backbone chain and an atom outside that chain, or a double or triple bond between two carbon atoms outside the backbone chain, will be treated according to the normal rules of organic nomenclature [13,14].
Monosaccharide derivatives having a double bond between two contiguous carbon atoms of the backbone chain are named by inserting, into the name for the corresponding fully saturated derivative, the infix 'x-en' followed by 'o' for euphony before a consonant. The infix is placed directly after the stem name that designates the chain length of the sugar. The locant x is the lower-numbered carbon atom involved in the double bond. Steric relations at a double bond are designated, if necessary, by the standard stereodescriptors '(Z)-' and '(E)-' preceding the whole name ([13], Section E). For multiple double bonds, infixes such as 'x,y-dien' are used (preceded by an inserted 'a' for euphony).
Note 1. The term 'glycal' is a non-preferred, trivial name for cyclic enol ether derivatives of sugars having a double bond between carbon atoms 1 and 2 of the ring. It should not be used or modified as a class name for monosaccharide derivatives having a double bond in any other position.
Note 2. Following the principle of first naming the saturated derivative, compounds having a C=CR-O- group as part of a ring system are named as unsaturated derivatives of anhydro alditols if R is hydrogen or carbon; if R is a halogen, chalcogen, or nitrogen-family element, the resulting name is that of a glycenose or glycenosyl derivative.
Note 3. The symbols (Z)- and (E)- may be omitted when the double bond is located within a ring system of six atoms or less, as steric constraints in such systems normally permit only one form.
Examples:
Methyl 2-deoxy-D-threo-pent-1-enofuranoside
1-(2-Deoxy-D-threo-pent-1-enofuranosyl)uracil
3,4-Di-O-acetyl-2-deoxy-D-erythro-pent-1-enopyranosyl chloride
2,6-Anhydro-1-deoxy-D-altro-hept-1-enitol
(alphabetic preference over 2,6-anhydro-7-deoxy-D-talo-hept-6-enitol)
1,2-Dideoxy-D-arabino-hex-1-enitol
(Z)-1,2,3,4,5-Penta-O-acetyl-D-erythro-pent-1-enitol
(E)-1,2,3,4,5-Penta-O-acetyl-D-erythro-pent-1-enitol
2-Deoxy-D-threo-pent-1-enose dimethyl acetal
2,3-Dideoxy-α-D-erythro-hex-2-enopyranose
1,2,4,5-Tetradeoxy-D-arabino-octa-1,4-dienitol
1,5-Anhydro-4-deoxy-D-erythro-hex-4-enitol
(enantiomeric precedence over 2,6-anhydro-3-deoxy-L-erythro-hex-2-enitol)
Methyl 3,4-dideoxy-β-D-glycero-hex-3-en-2-ulopyranoside
2,3-Dideoxy-α-D-glycero-hex-2-enopyranos-4-ulose
Methyl 3,4-dideoxy-β-D-glycero-hept-3-en-2-ulopyranosid-5-ulose
5-Deoxy-1,2-O-isopropylidene-β-L-threo-pent-4-enofuranose
5,6-Dideoxy-1,2-O-isopropylidene-α-D-xylo-hex-5-enfuranose
2-Carb-17.3. Triple bonds and cumulative double bonds
Monosaccharide derivatives having a triple bond or cumulative double bonds in the backbone chain are named by the methods of 2-Carb-17.2, with the infix 'n-yn' for a triple bond and infixes such as 'i,j-dien' for cumulative double bonds.
Note. This approach was not included in [5].
Alternatively they can be named on the basis of the corresponding fully saturated sugar by using the appropriate number of dehydro and deoxy prefixes (deoxy operations are regarded as formally preceding dehydro operations). The prefixes are placed in alphabetical order before the stem name.
Examples:
2-Deoxy-1-O-methyl-D-threo-pent-1-ynitol
or 1,1,2,2-tetradehydro-2-deoxy-1-O-methyl-D-threo-pentitol
6,7,8-Trideoxy-1,2:3,4-di-O-isopropylidene-α-D-galacto-octa-6,7-dienopyranose
or 6,7,7,8-tetradehydro-6,7,8-trideoxy-1,2:3,4-di-O-isopropylidene-
α-D-galacto-octopyranose
6-O-Acetyl-5-deoxy-α-D-xylo-hex-5-ynofuranose
o 6-O-acetyl-5,5,6,6-tetradehydro-5-deoxy-α-D-xylo-hexofuranose
5,6,8-Trideoxy-1,2-O-isopropylidene-α-D-xylo-oct-5-ynofuranos-7-ulose
or 5,5,6,6-tetradehydro-5,6,8-trideoxy-1,2-O-isopropylidene-
α-D-xylo-octofuranos-7-ulose
5. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN), Nomenclature of unsaturated monosaccharides (Recommendations 1980), Eur. J. Biochem., 119, 1-3 (1981); corrections: Eur. J. Biochem., 125, 1 (1982); Pure Appl. Chem., 54, 207-210 (1982); ref.2, pp. 162-164.
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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