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In chemistry, the Fischer projection, devised by Emil Fischer in 1891, is a two-dimensional representation of a three-dimensional organic molecule by projection. Fischer projections were originally proposed for the depiction of carbohydrates and used by chemists, particularly in organic chemistry and biochemistry .
As is depicted in a Fischer projection of D-threose, the adjacent substituents will have a syn orientation in the isomer referred to as "threo", and are anti in the isomer referred to as "erythro". [3] [4] Fischer projections depicting the two enantiomers of threose
L-Ribose Fischer Projection. Ribose is a simple sugar and carbohydrate with molecular formula C 5 H 10 O 5 and the linear-form composition H−(C=O)−(CHOH) 4 −H. The naturally occurring form, d-ribose, is a component of the ribonucleotides from which RNA is built, and so this compound is necessary for coding, decoding, regulation and expression of genes.
A Fischer projection can be used to differentiate between L- and D- molecules Chirality (chemistry). For instance, by definition, in a Fischer projection the penultimate carbon of D-sugars are depicted with hydrogen on the left and hydroxyl on the right. L-sugars will be shown with the hydrogen on the right and the hydroxyl on the left.
In aldohexoses the anomeric reference atom is the stereocenter that is farthest from the anomeric carbon in the ring (the configurational atom, defining the sugar as D or L). For example, in α-D-glucopyranose the reference atom is C-5. If in the cyclic Fischer projection [3] the exocyclic oxygen atom at the anomeric centre is cis (on the same ...
Nonetheless, the Fischer projection is a simple way of depicting multiple sequential stereocenters that does not require or imply any knowledge of actual conformation. A Fischer projection will restrict a 3-D molecule to 2-D, and therefore, there are limitations to changing the configuration of the chiral centers.
The L-isomers are generally absent in living organisms; however, L-altrose has been isolated from strains of the bacterium Butyrivibrio fibrisolvens. [6] When drawn in this order, the Fischer projections of the D-aldohexoses can be identified with the 3-digit binary numbers from 0 to 7, namely
The D/L system (named after Latin dexter and laevus, right and left), not to be confused with the d-and l-system, see above, does this by relating the molecule to glyceraldehyde. Glyceraldehyde is chiral itself and its two isomers are labeled D and L (typically typeset in small caps in published work). Certain chemical manipulations can be ...