Module 11 : Carbohydrates

Lecture 29 : Carbohydrates - I

11.3.1 Configuration of the Aldoses

Aldotetrose : The structural formula of aldotetrose is CH2OH·CHOH·CHOH·CHO. There are four stereoisomers (two pairs of enantiomers). Those stereoisomers correspond to D- and L-erythrose and D- and L-threose.

Aldopentose : The structural formula of aldopentose is CH2OH·CHOH·CHOH·CHOH·CHO. Since it contains three asymmetric carbons and there are eight stereoisomers (four pairs of enantiomers) possible. Those are the D- and L-forms of ribose, arabinose, xylose and lyxose.

Aldohexose : They have four asymmetric center and therefore 16 stereoisomers (eight pairs of enantiomers). The four D-altopentose and eight D-aldohexose are shown below.

Configuration of the D-Aldoses