L-Erythrose

The particular aldotetrose just shown is called d erythrose The prefix d tells us that the configuration at the highest numbered chirality center is analogous to that of d (+) glyceraldehyde Its mirror image is l erythrose... 

Relative to each other both hydroxyl groups are on the same side m Fischer pro jections of the erythrose enantiomers The remaining two stereoisomers have hydroxyl groups on opposite sides m their Fischer projections They are diastereomers of d and L erythrose and are called d and l threose The d and l prefixes again specify the con figuration of the highest numbered chirality center d Threose and l threose are enan tiomers of each other... 

Which aldotetrose is the structure shown Is it D erythrose D threose L erythrose or L threose (Be careful The conformation given is not the same as that used to generate a Fischer projection)... 

D-afe-o-Heptulose (sedoheptulose) (XXXVII) has been synthesized from D-erythrose (XXXVIII) plus triose phosphate, using an aldolase preparation from peas.169 Aldolases from yeast and from rat liver also form heptu-lose phosphate from these substrates.7S(o) 170(a) Crystalline muscle aldolase causes the formation of L-jrZwco-heptulose (XXXVIIa) from a mixture of L-erythrose (XXXVTIIa) and hexose diphosphate.170(b)... 

Lemer (29) reported a simple synthesis of L-erythrose that involves 2,3-di-O-isopropylidene-D-gulono-1,4-lactone (7b) as a key intermediate. Reduction of the lactone group of 7b with sodium borohydride, followed by periodate oxidation of the L-glucitol derivative, afforded 2,3-O-isopropy-lidene-L-erythrose. The free sugar may be readily obtained by acidic hydrolysis of the latter. 

The borohydride reduction-periodate cleavage applied to 2,3-O-isopro-pylidene-D-ribono- 1,4-lactone (16a) led to L-erythrose (30). The method was also employed (31) for the synthesis of D-erythrose, starting from an Obenzylidene-D-ribonolactone. However, in this case, the structural assignments for the intermediate compounds must be revised, as the starting material formulated as 3,5-O-benzylidene-D-ribono-1,4-lactone (2) was, as discussed previously in this section, the 3,4-0-benzylidene-D-ribono-1,5-lactone (3a). Therefore, the correct structure for the product described as 3,5-O-benzylidene-D-ribitol (20, not isolated) would be 3,4-O-benzylidene-... 

In the case of the above mentioned benzoyl-D-glucose derivatives a correlation was found between the formation of D-glucose dibenzamide and the permanent or transitory existence of a free aldehyde group. The same behavior was noted for triacetyl-oZdehydc-L-erythrose (XLI), which by the action of ammonia produces L-erjrthrose diacetamide (XLII). Isbell and Frush have obtained a similar result in the case of tetraacetyl-oWe/it/do-L-arabinose which, when treated with methanolic ammonia, gave L-arabinose diacetamide in 53 % yield. 

The tetroses (four-carbon sugars) have not yet been studied crystal-lographically, undoubtedly due to the lack of suitable crystals. Handbooks list D- or L-erythrose as a colorless syrup, and D- or L-threose as very hygroscopic, colorless, microscopic needles. The X-ray diffraction patterns for erythritol13 and for several derivatives of D- or L-tartaric acid have been solved. 

C-Methyl-L-erythrose (6) and derivatives 2-C-Methyl-D-erythrono-l,4-lactone (7)... 

For 2-dRL, the C(4 )-oxidized lesions (C4 -AP) and the lesion that has lost C(l ) (Erythrose-AP) is strong experimental evidence. 

T. Hudlicky, H. Luna, J. D. Price, and F. Rulin, An enantiodivergent approach to d- and L-erythrose via microbial oxidation of chlorobenzene, Tetrahedron Lett. 1989,... 

The eclipsed conformation shown, when oriented so that the aldehyde carbon is at the top, vertical bonds back, and horizontal bonds pointing outward from their stereogenic centers, is readily transformed into the Fischer projection of L-erythrose. 

This affords the L-acetal 10 via hypochlorite treatment of the intermediate 3,4-acetal of L-erythrose 9. The protected O-alkylidene glyceraldehydes are extremely flexible and can be converted into a plethora of other chiral synthons with a wide selection of uses using very standard chemical transformations (scheme 5). One major limitation for its use is the ease of racemization of the chiral center because of the ease of enolization of the aldehyde group. This is especially true even in the mildest of basic conditions. 

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