Pyruvate acetals

Treatment of a TIPDS group with methyl pyruvate (TMSOTf, 0° to rt, 69-99% yield) converts the group to the pyruvate acetal. ... 

Once citrate enters the cell, it is degraded to pyruvate, acetate, and carbon dioxide (Figure 13.8). Citrate lyase, one of the enzymes required for citrate metabolism, is induced by citrate in Leuconostoc spp. and heterofermentative lactobacilli (Mellerick and Cogan 1981). Since pyruvate is formed from citrate without the simultaneous production of reduced NAD, it does not have to be diverted to reoxidizing NAD, as is true for pyruvate formed from sugar fermentation. This surplus ... 

However, in the polysaccharides obtained from some mutant strains, there are deviations from this idealized structure.44 Xanthan is relatively resistant to enzymic hydrolysis, but it has been cleaved by an enzyme preparation from a Bacillus sp. at moderate temperatures and in the presence of buffer salts, yielding mono- and oligo-saccharides 45 A partially purified, enzyme preparation46 hydrolyzed deacetylated or depyruvated xanthan, and also xanthan from several wild-type and mutant strains of Xanthomonas. The release of reducing material varied little with xanthan preparations having differences in O-acetyl and pyruvic acetal contents. Under similar conditions of incubation, cellulase acted only on xanthan from mutant strains that had defective side-chain formation. 

T. Ziegler and G. Herold, Preparation of diastereomeric 3,4-O-pyruvate acetal-containing D-galactopyranose derivatives, structural assignment and use for oligosaccharide synthesis, Liebigs Ann. Chem., (1994) 859-866. 

Plasma Glucose Pyruvate Acetate Lactate 3-D-hydroxybutyrate ... 

Kan4N = kansosamine (4-amino-4-deoxy-3-C-methyl-2-(9-methylrhamnose) Ac = acetyl Fo = formyl Me = O-methyl Pyr = pyruvic acetal [4,6-0-(l-carboxyethylidene)]. 

The inner disaccharide unit of the trisaccharide hapten of the M. avium serovar 8 GPL148 was assembled in a manner similar to that of the serovar 20, but with reaction of the rhamnosyl trichloroacetimidate (80b) with the benzylidene acetal (81). O-Deacetylation of the product yielded the disaccharide acceptor (84) for the next glycosylation. Incorporation of the pyruvate acetal moiety into the terminal 3-O-methyl-D-glucose residue of 85 was achieved by transacetalation with methyl pyruvate diethyl dithioacetal, with sulfuryl chloride-triflic acid as catalyst. From the mixture of products the desired diastereomer was separated and converted by successive O-debenzylation, acetylation, selective 1-O-deacetylation, and reaction with trichloroacetonitrile into the trichloroacetimidate 86. Reaction of glycosyl donor 86 with acceptor 84, with trimethylsilyl triflate as promoter, afforded fully... 

Agarans are typically low in sulfate ester substitution, but those from numerous sources are rich in methyl ether or pyruvate acetal substitution in addition, glycosyl substitution (galactosyl, 4-O-methyl-L-galactosyl and/or xylo-... 

Rather uncommon are the two pyruvic acetal structures which have been identified in Klebsiella K12 capsular polysaccharides and in the teichoic acid of bacterium NCTC 9742 [10]. In the former case, a 4,5-0-(l-carboxyethylidene)- -D-galactofuranosyl residue was found at the side chain terminus of the hexa-saccharide repeating unit. In the latter case, the teichoic acid contains intra-catenally bound 2,3-0-(l-carboxyethylidene)-D-mannitol phosphate. No data about the configuration of these pyruvic acetals are available. 

The biosynthetic pathway of pyruvated oligo- and polysaccharides is not clear yet. However, it has been demonstrated for rhizobial polysaccharides that pyruvic acetal formation occurs at a late stage of the biosynthesis of the sugar chain. Furthermore, the pyruvic acid acetal is most probably introduced by an initial transfer of a propenoate-2-yl residue from phosphoenolpyruvate to a glycosyl residue followed by spontaneous ring closure [26]. 

Heidelberger demonstrated that the pyruvate acetal substituents of rhizobial polysaccharides behave as immunodominant groups. Furthermore, it has been shown that the configuration of the acetal group also influences the immunological properties of such saccharides [25, 28], and the existence of cross reactivities between pyruvated saccharides of different origin but bearing the same puruvic acid acetal are common phenomena. 

Since the formation of cyclic pyruvate acetals from alkyl pyruvates and diols under classical conditions (i.e. catalysis by acids) is expected to be unfavoured due to the necessity of the intermediate formation of a destabilized carbocation, early attempts to prepare 1-carboxyethylidene sugars used indirect procedures. Later, it was shown that under carefully controlled conditions the direct acetalation of a sugar diol with methyl pyruvate can also be used for preparative purposes. 

V-acetyl sialic acid, /V-glycolyl sialic acid, KDN, KDO, muramic acid sulfate, phosphate, phosphochollne, pyruvate, acetate... 

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