Gulose, configuration

Most substrates, with the exception of hydroxypymvate, have a threo configuration of hydroxyl groups at the C-3 and C-4 positions (139). The new stereocenter formed in TK-catalyzed addition is formed in the threo configuration with high diastereo-selectivity (151). Using TK-catalyzed condensations of hydroxypymvic acid with a number of aldehydes a practical preparative synthesis of L-idose [5934-56-5], L-gulose [6027-89-0], 2-deoxy-L-xylohexose, and... 

Before 1983, branched-chain sugars had not been found in bacterial polysaccharides, but there are now five examples belonging to this class. The LPS from Coxiella burned phase I contains both 6-deoxy-3-C-methyl-L-gulose (L-virenose) as pyranoside (12) and 3-C-(hydroxymethyl)-L-lyxose as furan-oside (13). Another 6-deoxy-3-C-methylhexose, having the manno configuration, is a component of the Nitrobacter hamburgiensis 0-antigen. ... 

D-Gulose (d-9) has also been prepared24 by the oxidation of 4,6-0-ethylidene-l,2-0-isopropylidene-a-D-galactopyranose (33), followed by reduction (resulting in overall inversion of the configuration of C-3) and hydrolysis. 

Oxidation of another hexose, (+ )-gulose, yields the same dicarboxylic acid, (+ )-glucaric acid, as does oxidation of (+ )-glucose. (The gulose was synthesized for this purpose by Fischer.) If we examine the two possible configurations for (+ )-glucaric acid. Ilia and IVa, we see that only Ilia can be derived from two different hexoses from III and the enantiomer of V. 

So far in our discussion, we have seen how configurations III, IV, V, and X of the previous section were assigned to (+)-glucose, (+)-mannose, (-)-gulose. 

ProUem 34.19 The f+)-gulose that played such an important part in the proof of configuration of o-(+)-glucose was synthesized by Fischer via the following sequence ... 

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