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Lecture 37 – Chapter 25 : Carbohydrates

Lecture 37 – Chapter 25 : Carbohydrates. Fischer projections Cyclic forms – hemiacetal formation, 6 vs. 5 Mutarotation Glycosides – formation and examples Disaccharides Oligosaccharides and Polysaccharides Miscellaneous reactions. Simple monosaccharides – Fischer depictions.

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Lecture 37 – Chapter 25 : Carbohydrates

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  1. Lecture 37 – Chapter 25 : Carbohydrates • Fischer projections • Cyclic forms – hemiacetal formation, 6 vs. 5 • Mutarotation • Glycosides – formation and examples • Disaccharides • Oligosaccharides and Polysaccharides • Miscellaneous reactions

  2. Simple monosaccharides – Fischer depictions D-glucose D-galactose D-glucosamine N-acetyl-D-glucosamine D-FucNAc D-ManAcA D-Ribose 2-Deoxy-D-ribose

  3. Aldohexoses – cyclic forms and their interconversion All present in solution, free sugars can interconvert

  4. Mutarotation • dissolve dextrose in water, measure [a]D : +112.2 • dissolve b-D-glucopyranose in water, measure [a]D : +18.7 • allow either to equilibrate, measure [a]D : +52.5

  5. Glycosides • Free sugar + alcohol + acid gives a glycoside • Glycosides are no longer free sugars and do not mutarotate

  6. Glycosides - disaccharides • Organic synthesis limited by protecting group chemistry needed • Bioorganic enzymatic synthesis now making oligosaccharides

  7. Disaccharides – examples

  8. Oligosaccharides – examples • Blood group antigens – extremely subtle differences in sugars in the epitope lead to important consequences in blood biochemistry

  9. Polysaccharides – examples amylose cellulose

  10. Synthetic vaccines Danishefsky et. al. Sloan-Kettering/Columbia – Synthetic vaccine against 3 types of cancer

  11. Miscellaneous reactions of free sugars

  12. Friday • Chapter 26 – Lipids and fats

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