Aldose table

From their kinetic results Bishop and collaborators >8) calculated the velocity constants of the furanoside anomerisations of their seven aldoses (Table 1), and rationalised them in terms of ring conformations and group interactions. Thus, for example, in the extreme cases methyl a-D-arabinofuranoside (4), having the fewest non-bonded steric interactions, is the most stable pentofuranoside, while methyl p-o-lyxofurano-side (5), having the least stable ring, reacts most rapidly. 

Over 200 different monosaccharides are known They can be grouped according to the number of carbon atoms they contain and whether they are polyhydroxy aide hydes or polyhydroxy ketones Monosaccharides that are polyhydroxy aldehydes are called aldoses, those that are polyhydroxy ketones are ketoses Aldoses and ketoses are further classified according to the number of carbon atoms m the mam chain Table 25 1 lists the terms applied to monosaccharides having four to eight carbon atoms... 

In order to characterize them and more readily separate them from interfering accompanying substances carbonyl compounds (aldehydes, ketones) can be converted to hydrazones at the start. The reagent mainly employed is 2,4-dinitro-phenylhydrazine in acidic solution [70], This yields osazones with aldoses and ketoses. Some examples are listed in Table 15. 

Commercial A -acetylneuraminic acid aldolase from Clostridium perfringens (NeuAcA EC 4.1.3.3) catalyzes the addition of pyruvate to A-acetyl-D-mannosamine. A number of sialic acid related carbohydrates are obtained with the natural substrate22"24 or via replacement by aldose derivatives containing modifications at positions C-2, -4, or -6 (Table 4)22,23,25 26. Generally, a high level of asymmetric induction is retained, with the exception of D-arabinose (epimeric at C-3) where stereorandom product formation occurs 25 2t The unfavorable equilibrium constant requires that the reaction must be driven forward by using an excess of one of the components in order to achieve satisfactory conversion (preferably 7-10 equivalents of pyruvate, for economic reasons). 

Monosaccharides are those carbohydrates that cannot be hydrolyzed into simpler carbohydrates They may be classified as trioses, tetroses, pentoses, hex-oses, or heptoses, depending upon the number of carbon atoms and as aldoses or ketoses depending upon whether they have an aldehyde or ketone group. Examples are listed in Table 13-1. 

Taste studies of reducing disaccharides containing a reducing ketose residue have also been conducted (see Table XV). In contrast to the aldoses, results obtained with palatinose (36), maltulose (37), lactulose... 

Table 1 Reaction of aldoses with pentane-2,4-dione (1) or ethyl acetoacetate (2)...

Schnur and colleagues at Pfizer " " prepared a wide variety of 2,4-oxazoli-dinediones that have been evaluated as hypoglycemic agents and as aldose reductase inhibitors (Tables 6.8, Fig. 6.17 6.9, Fig. 6.18 Fig. 6.19). Several approaches were evaluated including a trimethylsilylcyanide-mediated synthesis of cyanohydrins that were then converted to the corresponding imidates in situ followed by cyclization and work-up. This methodology has been successfully... 

Imperial Chemical Industries (ICI) chemists " prepared a novel series of spirocyclic 2,4-oxazolidinediones 243 derived from 7-substituted isatins (Scheme 6.54). The key intermediate a-acyloxy amides 242 were readily prepared from 241 in three steps. Base-catalyzed cyclization of 242 then afforded the target compounds that were reported to be potent inhibitors of aldose reductase. Pfizer chemists approached 5-substituted isatin spirocyclic analogues 243 via a-hydroxy esters 244 that were converted to the corresponding a-carbamyloxy esters 245 in good yield using chlorosulfonyl isocyanate. Cyclization of 245 with potassium ferf-butoxide then produced 243 in acceptable yield (Scheme 6.54 Table 6.10, Fig. 6.20). 

The following Tables list the aldose oxirane derivatives that have been prepared. The solvents used in determination of the specific rotation are given by A, acetone C, chloroform E, Ethanol E.A., ethyl acetate M, methanol P, pyridine and W, water. 

Table 2.2.6.1 Ketoses and aldoses tested as acceptor substrates of recombinant SuSyl expressed in yeast.

Diols and polyols can participate in equilibria with boric acid in aqueous solution. The stability of polyolborates is determined by the number of OH groups in cis positions. Complexes with polyols are more stable than with diols, and 1,2-diol complexes are more stable than their 1,3-diol counterparts (Table 10) since the resulting five-membered chelate ring is unstrained.75120 In the case of 1,3,5-triols stable cage-like structures (5) and (6) are favored. Open-chain or five-membered cyclic polyols form more stable chelate complexes than their six-membered counterparts.120 Thus, chelates from alditols and ketohexoses are more stable than the corresponding aldose chelates (Table 10). Many polyols allow quantitative titrimetric determination of boric acid. Of these, mannitol remains the most widely used reagent on the basis of availability, cost and ease of handling.75... 

Percentage of the two pyranose forms, but not of all forms of the aldose. Calculated from the data in Table II. 

Water is the only solvent in which the composition of sugars has been systematically explored. Stevens1674 has determined the composition of several aldoses in pyridine-d5 by -n.m.r, spectroscopy at 300 MHz. There are scattered data on solutions in organic solvents (mainly pyridine, dimethyl sulfoxide, and N,N-dimethylformamide), but only rarely have four (or more) components of such solutions been quantitatively determined. The data that have been encountered are collected in Table VII undoubtedly, there are others that have been missed. 

Table IV, which briefly summarizes the material described in previous sub-sections, shows the total of the different monosaccharide components identified in bacterial polysaccharides, and our present knowledge about their activated forms. It may be seen that identification of the activated forms has been achieved for only approximately half of the monosaccharides known to be involved. The most striking gap in the information available is the lack of data about the activated forms of D-ribose-derived monosaccharides and of most of the D-fructose-derived aldoses having configurations other than gluco, galacto, and manno.

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