- Aldohexose
An "aldohexose" is a
hexose with analdehyde group on one end.The aldohexoses have four
chiral centre s for a total of 16 possible aldohexosestereoisomer s (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 thehydroxyl at position 5, and does not refer to the direction ofoptical activity .There are eight D-aldohexoses:
CH=O CH=O CH=O CH=O
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HC-OH HO-CH HC-OH HO-CH
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HC-OH HC-OH HO-CH HO-CH
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HC-OH HC-OH HC-OH HC-OH
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HC-OH HC-OH HC-OH HC-OH
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CH2-OH CH2-OH CH2-OH CH2-OH D-Allose D-Altrose D-Glucose D-Mannose CH=O CH=O CH=O CH=O
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HC-OH HO-CH HC-OH HO-CH
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HC-OH HC-OH HO-CH HO-CH
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HO-CH HO-CH HO-CH HO-CH
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HC-OH HC-OH HC-OH HC-OH
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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 sulfolipidSQDG .
*L-Pneumose (6-deoxy-L-talose)
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