D-mannose
- Used in protein glycosylation
- C2- 5: chiral = 2^4 = 16 different stereoisomers
- D-mannose & D-glucose are diastereomers: not mirror images, differ in spatial arrangement of atoms at C2
- D-mannose & D-glucose are epimers: only differ at one stereocenter, C2
Instructions for drawing D-mannose:
- First, draw a vertical chain of six carbons.
- Label the carbon atoms 1-6 from top to bottom.
- To carbon 1, add a carbonyl group and a hydrogen atom.
- To carbons 2 and 3 add a hydroxyl group on the left and a hydrogen atom on the right.
- For carbons 4 and 5 add a hydrogen atom on the left and a hydroxyl group on the right.
- Finally, on carbon 6 add two hydrogen atoms and a hydroxyl group.
- Indicate that this molecule is D-mannose, a sugar commonly used in the glycosylation of proteins.
- Notice that there are 4 carbons (2 through 5) that are all chiral (shown in pink); thus, giving 2 to the power of 4 (which equals 16) different stereoisomers.
- Only a few of these are generally considered relevant to human biochemistry.