L- -glyceraldehyde

Identify each of the following as either o or l glyceraldehyde CH2OH H CHO... 

Highest numbered chirality center has configuration analogous to that of - L glyceraldehyde... 

At the present time, use of the Fischer convention is almost entirely restricted to carbohydrates, amino acids, and biologically important molecules of closed related structural types. The problem with more general use is that there are no adequate rules for deciding whether a diiral atom is like D-glyceraldehyde or L-glyceraldehyde when the structures are not closely similar to the reference molecules. This relationship is clear for carbohydrates and amino acids. 

Absolute configurations of the amino acids are referenced to D- and L-glyceraldehyde on the basis of chemical transformations that can convert the molecule of interest to either of these reference isomeric structures. In such reactions, the stereochemical consequences for the asymmetric centers must be understood for each reaction step. Propose a sequence of reactions that would demonstrate that l( —)-serine is stereochemically related to l( —)-glyceraldehyde. 

With L-glyceraldehyde as substrate, the same extract catalyzed a half-gram scale synthesis of 1 -deoxy-L-f/ueo-pentulose. 

Once the configuration of the glyceric acids was known (in relation to the glyceraldehydes), it was then possible to relate other compounds to either of these, and each time a new compound was related, others could be related to it. In this way, many thousands of compounds were related, indirectly, to d- or L-glyceraldehyde, and it was determined that 34, which has the d configuration, is the isomer that... 

Periodate oxidation of 5,6-O-isopropylidene-L-gulono-1,4-lactone (9a) gave 2,3-O-isopropylidene-L-glyceraldehyde in 69% yield. This compound was used to prepare 2,3-O-isopropylidene-L-glycerol and it was also condensed with amines and Wittig reagents (34). 

Figure 10.4 The stereochemical relationship between amino acids and glycer-aldehyde. The designation of d or l to an amino acid refers to its absolute configuration relative to the structure of d- or L-glyceraldehyde respectively. The d and l forms of a particular compound are called enantiomers.

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