Cyclitol
In
nH
2n-x(OH)
x or C
nH
2nO
x where 3 ≤ x ≤ n.
The name is also used for compounds that can be viewed as result of substituting various functional groups for the hydrogen atoms in such a molecule, as well as similar molecules with one or more double bonds in the ring.[citation needed]
Cyclitols and their derivatives are some of the compatible solutes which are formed in a plant as a response to salt or water stress. Some cyclitols (e.g. quinic or shikimic acid) are parts of hydrolysable tannins.
Isomerism and nomenclature
Unsubstituted cyclitols with the same ring size and number of hydroxyls may exist in several structural isomers, depending on the position of the hydroxyls along the ring. For example, cyclohexanetriol exists in three distinct isomers (1,2,3-, 1,2,4-, and 1,3,5-).
Furthermore, the hydrogen and the hydroxyl on each carbon atom may lie in two possible arrangements relative to the local ring plane; so that each structural isomer may exist in several
Naturally occurring cyclitols
Unsubstituted
- Conduritol, or cyclohex-5-ene-1,2,3,4-tetrol; two out of ten possible isomers.
- Inositol, or cyclohexane-1,2,3,4,5,6-hexol; four out of nine possible isomers.
- Cyclohexanetetrol[3]
Substituted
- Bornesitol; (1R,2R,3S,4S,5R,6S)-6-methoxycyclohexane-1,2,3,4,5-pentol; D-(−)-O-methyl-myo-inositol
- Pinitol; (1S,2S,4S,5R)-6-methoxycyclohexane-1,2,3,4,5-pentol; 3-O-methyl-D-chiro-inositol
- Ononitol; (1R,2S,3S,4S,5S,6S)-6-methoxycyclohexane-1,2,3,4,5-pentaol; 4-O-methyl-myo-inositol
- Pinpollitol; (1R,2R,3R,4S,5R,6S)-3,6-dimethoxycyclohexane-1,2,4,5-tetraol; di-O-methyl-(+)-chiro-inositol
- Quebrachitol; (1R,2S,4S,5R)-6-methoxycyclohexane-1,2,3,4,5-pentol; 2-0-methyl-chiro-inositol
- Quinic acid; (1S,3R,4S,5R)-1,3,4,5-tetrahydroxycyclohexanecarboxylic acid
- Shikimic acid; (3R,4S,5R)-3,4,5-trihydroxycyclohex-1-ene-1-carboxylic acid
- Valienol; (1S,2S,3S,4R)-5-(Hydroxymethyl)cyclohex-5-ene-1,2,3,4-tetrol
- Viscumitol (1R,2S,3R,4S,5R,6S)-5,6-dimethoxycyclohexane-1,2,3,4-tetraol; 1,2-di-O-methyl-muco-inositol
Glycosides
- Ciceritol, a pinitol digalactoside
Phosphates
- Phytic acid; (1R,2S,3r,4R,5S,6s)-cyclohexane-1,2,3,4,5,6-hexayl hexakis[dihydrogen(phosphate)]; inositol hexakisphosphate
Other cyclitols
Analysis methods
In 1955,