User:Benjah-bmm27/degree/3/MCG

Carbohydrates, MCG

Important functions and applications

• Salicin and its derivative, aspirin: Jmol
• Heparin and related anticoagulants: low molecular weight heparin, fondaparinux, idraparinux
• ABO blood group system

Common sugars

• Glucose: Jmol models from the crystal structures of both the α and β anomers.
  • N-Acetylglucosamine
• Galactose
  • N-Acetylgalactosamine
• Mannose
• Fucose — the only sugar that naturally occurs as the L-enantiomer
• Fructose

Carbohydrate structures and conformations

Hemiacetals and mutarotation

• Hemiacetal formation
  • alcohol + aldehyde → hemiacetal
  • acid promotes forward reaction, base promotes reverse
  • new chiral centre formed
  • In monosaccharides, the new chiral centre is called the anomeric carbon

• Mutarotation of hemiacetals
  • α and β anomers of monosaccharides interconvert
  • α hemiacetal → aldehyde + alcohol → β hemiacetal
  • In solution, glucose is:
    • 36 % α-D-glucopyranose
    • 63 % β-D-glucopyranose
    • 0.003 % open chain aldehyde
    • negligible proportions exist as α-D-glucofuranose and β-D-glucofuranose

Ring conformation

• For glucose, ⁴C₁ conformation preferred to ¹C₄ as the former has all equatorial groups, latter has all axial

Anomeric effect

• Anomeric effect

Protecting groups

• Protecting group

For alcohols

• Esters
  • Acetates - but beware acetates 'walking' around the ring
  • Benzoates
• Ethers
  • Benzyl
  • Methoxymethyl

Glycosylation reactions

• Glycosylation

External links

• RJC's Level 3 web notes: Monosaccharides and Amino Acids