Fisher projection

Scheme 1.1 Typical steric defects in a (mainly) isotactic poly-l-alkene chain (adapted Fisher projections) for (a) chain-end-stereocontrol (b) enantiomorphic site stereocontrol.

Figure 11. Schematic representation of iso-, syndio- and atactic polymers, parts a, b and c, respectively. Chain segments are shown in their trans-planar and modified Fisher projections.

An early method to picture the three-dimensional properties of molecules was the use of Fischer projections. In Fisher projections, bonds are drawn either vertically or horizontally. Bonds which are vertical project into file space behind the plane of file paper (blackboard, computer screen). Bonds which are horizontal project into file space in front of file plane of the paper (blackboard, computer screen). 

By extension, other diastereomeric pairs of molecules which contain two adjacent stereogenic centers can be designated as tlireo or erythro depending on whether substituents extend to opposite (threo) or the same (erythro) sides of the Fisher projection of the molecule. For example,... 

Fisher-projection diagram depicts chiral/3-D structure... 

Figure 9.22 Traditional Fisher projection of the two glucose sterioisomers—one reflects plane-polarized fight to the right [dextrorotatory (d)] and the other reflects it to the left [levorotatory (l)].

Figure 17.1. Fisher projection used in the stereospecific numbering of a triacylglyceride.

In a Fischer projection, the bonds to the central carbon are represented by horizontal and vertical line.s from the substituent atoms to the carbon atom, which is assumed to be at the center of the cross. By convention, the horizontal bonds are assumed to project out of the page toward the viewer, whereas the vertical bonds are assumed to project behind the page away from the viewer. The Glossary of Compounds lound at the back of the book is a structural glossary of the key molecules in biochemistry, each presented in two forms with stereochemically accurate bond angles and as a Fisher projection. 

Figure 2.14 Diagrams of (a) isotactic, (b) syndiotactic, and (c) atactic configurations of -(CH2-CXY-)n— polymer. The corresponding Fisher projections are shown on the right.

Scheme 7. Chziin Segments Are Shown in Their trans-Planar ind Modified Fisher Projections...

Make sure the group with lowest priority (d) is on a vertical bond to determine R/S in a Fisher projection ... 

The chemistry involved in this isomerization is easiest to see by considering the open-chain (Fisher projection) forms of these two monosaccharides ... 

An a-amino acid contains an amino group a carboxyl group, a hydrogen atom and a distinctive R group - all of these are bound to an a-carbon atom. Amino acids in solution at neutral pH are in their zwitterionic form i.e., the -NH2 is present in the form of -NHa and the -C(X)H is present in the form of a deprotonated COO. This may be represented in the wedge and Fisher projection forms (Fig. 2.1). 

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