Natural Product Biomolecules - Organic Chemistry Concepts: An EFL Approach - page 165

QUESTIONS AND PROGRAMS
Q 8.1. Classify the following simple sugars (monosaccharides).

PROGRAM 25 Fischer/Haworth Diagrams
A It can be difficult at first to classify carbohydrates by their chirality centers. This is
because there can be many chirality centers in the carbon backbone. This concept is
simply an extension of stereoisomerism from Chapter 3. We now take a look at what
this looks like for carbohydrate examples.

For single chirality centers you have seen perspective drawings. We now introduce the
Fischer projection formula. This is best explained by an example.

Try to show what the Fischer projection rules are.

B It should be clear that all vertical bonds project into the plane of the paper, and all
horizontal bonds project out of the plane of the paper. In the case of carbohydrates the
arrangement of the ligands is also important. The most oxidized ligand, either aldehyde
or ketone, is drawn at the top of the vertical axis and the most reduced -CH 2 OH end is
at the bottom.

Continued...