Aldohexose
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An aldohexose is a hexose with an aldehyde group on one end.
The aldohexoses have four chiral centres for a total of 16 possible aldohexose stereoisomers (24). Of these, only three commonly occur in nature: D-glucose, D-galactose, and D-mannose. The D/L configuration is based on the orientation of the hydroxyl at position 3, and does not refer to the direction of optical activity.
There are eight D-aldohexoses:
CH=O CH=O CH=O CH=O | | | | HC-OH HO-CH HC-OH HO-CH | | | | HC-OH HC-OH HO-CH HO-CH | | | | HC-OH HC-OH HC-OH HC-OH | | | | HC-OH HC-OH HC-OH HC-OH | | | | CH2-OH CH2-OH CH2-OH CH2-OH D-Allose D-Altrose D-Glucose D-Mannose
CH=O CH=O CH=O CH=O | | | | HC-OH HO-CH HC-OH HO-CH | | | | HC-OH HC-OH HO-CH HO-CH | | | | HO-CH HO-CH HO-CH HO-CH | | | | HC-OH HC-OH HC-OH HC-OH | | | | CH2-OH CH2-OH CH2-OH CH2-OH D-Gulose D-Idose D-Galactose D-Talose
Deoxyaldohexoses
Aldohexoses can have one or more of their hydroxyl groups replaced by hydrogens to form deoxyaldohexoses. The following are well known cases of such compounds :
- L-Fucose (6-deoxy-L-galactose)
- L-Rhamnose (6-deoxy-L-mannose)
- D-Quinovose (6-deoxy-D-glucose)
Quinovose is found as part of the sulfolipid SQDG. - L-Pneumose (6-deoxy-L-talose)de:Hexosen#Die_Aldohexosen
