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Clinical pharmacy PharmD program Third level Phytochemistry-1 (PG-504)

• Since the simplest sugar molecule, glyceraldehyde, has an asymmetric carbon

atom, it will be optically active. Consequently, it has two stereoisomers “a pair

of enantiomers or antipode”, which are mirror images to each other. The

isomer having the OH group to the right has given the name D-glyceradehyde,
while its enantiomer having the OH group to the left was given the name L-

glyceraldehyde.

• Molecules which are enantiomers of each other have exactly the same physical
properties (melting point, boiling point, index of refraction, etc.) but not their

interaction with polarized light.

n
Van’t Hoff’s 2 rule

When a molecule has more than one chiral carbon, each carbon can possibly be

arranged in either the right-hand or left-hand form, thus if there are n chiral

n
carbons, there are 2 possible stereoisomers.

Maximum number of possible stereoisomers = 2 n 


➢ The aldo hexoses have 4 asymmetric carbons and therefore
exist as 16 possible stereo isomers. These can be divided 


into two enantiomeric sets of eight diastereomers.
4
Aldoses: 4 asymmetric carbons so 2 = 16 stereoisomers

D- Glucose

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