Cyclitol

In organic chemistry, a cyclitol is a cycloalkane containing at least three hydroxyl, each attached to a different ring carbon atom.^[1] Most commonly, cyclitol refers to cyclic sugar alcohol.^[2] Cyclitols and their derivatives are some of the compatible solutes that are formed in a plant as a response to salt or water stress. Cyclitols are minor components of trees.^[3] Some cyclitols (e.g. quinic or shikimic acid) are parts of hydrolysable tannins.

inositol is a common cyclitol.

Even simple cyclitols can be complicated from the perspective of stereochemistry. For example, cyclohexanetriol exists in three isomers (1,2,3-, 1,2,4-, and 1,3,5-). Furthermore, nine stereoisomers are possible for 1,2,3,4,5,6-cyclohexanehexol (inositol), two of them being enantiomers.

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^[4]

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

• 1,2,3,4-Cyclohexanetetrol^[5]
• 1,2,3,4,5-Cyclopentanepentol

Applications

Aside from their utility to plants, cyclitols are useful as precursors to synthetic materials.^[6]

Analysis methods

Théodore Posternak and others described the separation of cyclitols by paper chromatography using three methods of development: Tollens reagents, the Meillère reagent (based on the Scherer-Gallois reaction), and digestion by Acetobacter suboxydans followed by Tollens reagent.^[7]

Further reading

Nomenclature for cyclitol stereoisomers:CON and CBN IUPAC Commissions on Nomenclature (1968): "The Nomenclature of Cyclitols - Tentative Rules". European Journal of Biochemistry, volume 5, pages 1-12. doi:10.1111/j.1432-1033.1968.tb00328.x

See also

• Aminocyclitol