Mannopyranose

The specific optical rotations of pure a and p o mannopyranose are +29 3° and -17 0° respectively When either form is dissolved in water mutarotation occurs and the observed rotation of the solution changes until a final rotation of +14 2° is observed Assuming that only a and p pyranose forms are present calculate the percent of each isomer at equilibrium... 

Fig. 9. Partial structural formulas and shorthand notations for principal hemiceUuloses found in wood, where the sugar units ate noted as P-D-xylopyranose (Xylp), 4-Omethyl-a-D-glucopyranosyluronic acid (GlupU), a-L-arabinofuranose (Araf), P-D-glucopyranose (Glup), P-D-mannopyranose (Manp), and P-D-galactopyranose (Galp) for (a) arabino-4-O-methylglucuronoxylan from softwood, (b) 0-acetyl-galactoglucomannan from softwood, and...

Table IV. Comparison of Anomeric Proton (Hi) Chemical Shifts for Free and Acetylated D-gluco and D-mannopyranoses With Those of Related 2-Deoxy Sugar Derivatives. Effect of Replacing an Axial or an Equatorial C2-Methylene Proton With a Hydroxy or Actetoxy Substituent...

Problem 25,13 Draw /3-o-galactopyranose and jS-D-mannopyranose in their more stable chair conformations. Label each ring substituent as either axial or equatorial. Which would you expect to be more stable, galactose or mannose ... 

I4l6-Tii-0-benzoyl-[(S)-1,2-0-chloro(methoxy)methylene]-p-D-mannopyranose... 

Whereas the backbone of the first type is made up exclusively of /1-(1 4)-hnked o-mannopyranose (o-Manp) residues in Hnear chains, the second type... 

On the other hand, if substitutions of 37 were conducted with benzoate ions, instead of acetate ions, direct Sn2 reactions occurred predominantly, and carba-y -DL-mannopyranose pentaacetate (41) was obtained. ... 

Carba-a-D-galactopyranose (7) has also been synthesized from quebrachi-tol, by Paulsen and coworkers,as well as carba- -D-mannopyranose (114). 

From L-arabinose, carba-sugars of the a-D-gluco and h-altro types were prepared from D-arabinose, carba-a-L-mannopyranose from D-ribose, that of the fi-L-manno modification from D-xylose, those of the -L-gluco and a-D-altro forms and, from D-glucose, those of the P-L-allo a-L-... 

Section III, 3,a. From 133, carba-a-L-mannopyranose pentaacetate (135) was produced as follows. 

Compound 138 was converted into carba- -L-mannopyranose pentaace-tate (139) in the usual way. - ... 

Similarly, the mannopyranosyl analog (346) was synthesized by condensation of di-O-isopropylidene-a-DL-carba-mannopyranose (349) with 348. The other isomer (347) was obtained by reaction of 278 with tetra-O-benzoyl-a-D-mannopyranosyl bromide (350). The four carba-glucopyrano-syl D-mannopyranosides, including 346 and 347, show no antiviral activity. 

As 2-amino-2-deoxy-D-mannose is tumorstatic and 2-acetamido-2-deoxy-D-mannose 6-phosphate is an obligatory intermediate in the biosynthetic pathway to sialic acid, displacement of the essential OH-6 with a fluorine atom should be interesting from the biological viewpoint. 2-Acetamido-1,3,4-tri-0-acetyl-2,6-dideoxy-6-fluoro-D-mannopyranose (see Table 111 in Section 11,3) and its O- and A,0-deacetyl derivatives were prepared the first compound showed weak anticancer activity. 

A-Acetyl-9-deoxy-9-fluoroneuraminic acid (591) was prepared by treatment of a protected 6-hydroxyl precursor with A, A-diethylaminosulfur trifluoride (DAST) or through condensation of 2-acetamido-2,6-dideoxy-6-fluoro-D-mannopyranose with potassium di(/ >r/-butyl) oxaloacetate. Compound 591 is a substrate for cytidine monophosphate (CMP)-sialic acid synthetase, giving rise to CMP-5-A-acetyl-9-deoxy-9-fluoroneuraminic acid, which is cytotoxic against tumor cells. 5-A-Acetyl-3-fluoroneuraminic acids 592-594 were prepared through fluorine (or acetyl hypofluorite) addition (in AcOH) to methyl 5-acetamido-4,7,8,9-tetra-0-acetyI-2,6-anhy-dro-2,3,5-trideoxy-D- /ycm>D- a/arto-non-2-enopyranosate. Compound 592 was found to be a potent neuraminidase inhibitor. 

Acetamido-2-deoxy-D-galactopyranose (—), and 2-Acetamido-2-deoxy-D-mannopyranose ( ) at Anomeric Equilibrium in Aqueous Solution (redrawn from Ref. 28), and 2-Acetamido-2-deoxy-D-glucopyranose (- -) at Anomeric Equilibrium in Aqueous Solution. (Redrawn from Ref. 29.)... 

Support for this result was obtained from the taste of 1,5-anhydrohexitols, which, only for purposes of comparison, can be regarded as 1-deoxyal-dopyranoses. 1,5-Anhydro-D-glucitol (that is, the incorrectly named 1-deoxy-D-glucopyranose ) (14), 1,5-anhydro-D-mannitol ( 1-deoxy-D-mannopyranose or 2-deoxy-D-fructopyranose ) (15), and 1,5-anhydro-D-galactitol ( l-deoxy-o-galactopyranose ) (16) are all purely sweet, without any trace of bitterness. Furthermore, the complete absence of bitterness of 1,5-anhydromannitol (16) clearly indicates that the anomeric... 

C-5, C-3, C-2, C-4, and C-6 of a-D-mannopyranose. There is very little / -D-mannopyranose present. Peaks 14,15,16,19, and 24 (see Fig. 4) can readily be assigned to a-D-glucopyranose. These results corroborated the findings by other researchers as to the types of carbohydrates present in glucoamylase.104... 

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