Of galactopyranose

Perform the following tasks using the protein sequence of-galactopyranose mutase... 

The hypothesis of Praefcke et al. [345], that geminally branched amphiphiles form, by association, disk-like units, has been proved also for the case of galactopyranose derivatives [348, 349]. 

Figure 4 HSQC correlation spectrum of galactopyranose pi-4glucopyranose at 500 MHz and 303 K in HjO. Resonances are labelled with the appropriate assignment for each correlation. In practice, these can be relatively easily identified by comparison with previously assigned proton or carbon chemical shifts. Reproduced by courtesy of Homans SW and Kiddle GR, University of St. Andrews.

From the rearrangement of tetra-O-acetyl-2-hydroxy-D-galactal in boiling acetic acid it was possible to isolate l,2,4,6-tetra-0-acetyl-2,3-dide-h.ydro-3-deoxy-a-jy-threo-hexose (32) (58%) and a small amount of 1,2,3,4,6-penta-O-acetyl-jS-D-galactopyranose. In the reaction mixture the presence of some a-pentaacetate was demonstrated chromatographically but NMR spectroscopy indicated no resonances corresponding to the / anomer of compound 32. These spectral measurements indicate that compound 32 constituted 80% of the mixture of products. 

The only recorded example using this method in the sugar series is the chlorination of l,2 3,4-di-0-isopropylidene-D-galactopyranose (73) which affords in addition to the expected 6-chloro-6-deoxy derivative 74a, a 5,6-unsaturated derivative 75 as well. These products were separated by silica gel column chromatography no yields were given. 

Epimerization of 4 at C-2 provided 5a-carba-a-DL-galactopyranose (6). When the pentaacetate IS was heated in acetic acid containing sulfuric acid, epimerization occurred at C-2 through an intermediary cyclic acetoxonium ion (18), with anchimeric assistance of the vicinal, axial acetoxyl group. After acetylation, 5a-carba-a-DL-galactopyranose pentaacetate (19) was obtained in a yield of 14% it was converted into 6 by hydrolysis. The antimicrobial activity of the racemate 6 was found to be about half that of the natural antibiotic 7 in the same assay system, indicating that the L-antipode is probably inactive. " ... 

Starting from (—)-29, carba-a-D-galactopyranose (7) and carba-) -D-glu-copyranose (94) have been synthesized by a reaction analogous to that employed in the preparation of the racemates. - ... 

The 4-0- (282) and 4,7-di-O-methanesulfonates (283) of a-DL-carba-galactopyranose obtained from 258 produced, after azidolysis in DMF, hydrogenolysis, and acetylation, penta-A, 0-acetyl-4-amino- (284) and 4,7-diamino-4,7-dideoxy-o -DL-carba-glucopyranose (285). 

As mentioned earlier, a-D-carba-galactopyranose (1) has been found in a fermentation broth of Streptomyces sp. MA-4145, as an antibiotic. The potency of the antibiotic was rather low. A concentration of—125 fig/mh is required in order to produce a standard inhibition zone of 25-mm diameter against Klebsiella pneumoniae MB-1264, using 13-mm assay discs in a disc-plate assay. A sample of the synthetic a-DL-carba-galactopyranose (17) was... 

Difluoro compounds have been prepared by treatment of carbonyl compounds with DAST. These are methyl 5-deoxy-5,5-difluoro-2,3,-0-isopropylidene-)S-D-ribofuranoside, 6-deoxy-6,6-difluoro-1,2 3,4-di-0-isopropylidene-a-D-galactopyranose, methyl 2-deoxy-2,2-difluoro-... 

Agarose is closely approximated as the alternating copolymer of (1 3)-/3-D-galactopyranose and (l- 4)-3,6-anhydro-a-L-galactopyranose (see formula 5). 

Fig. 17.—Circular Dichroism of 2-Acetamido-2-deoxy-D-galactopyranose at Anomeric...

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