Tetrose sugars

Erythritol (= 1,2,3,4-Butanetetrol) (tetrose sugar alcohol) Papaver somniferum (Papaveraceae), Primula sp. (Primulaceae), Poaceae green algae, fungi, lichens Sweet (2 X >sucrose)... 

As an illustration of the importance of selective dehydration, the reaction of tetrose sugars in alcoholic media with soluble Sn halides has recently been reported [100]. This presents a homogeneous catalytic system, which delivers both Brpnsted (as HCl) and Lewis (as Sn " or Sn" " ) acids. The final products of this conversion were useful a-hydroxy-acids, such as vinyl glycolic acid as discussed in detail in Chap. 3 of this volume (Dusselier et al.). The first step in the reaction path involves a double dehydration leading to the proposed intermediate vinyl glyoxal, as shown being derived from the tetrose in Fig. 12. The mechanism of the dehydration of tetroses is shown in more detail in steps 1 and 2 in Fig. 13 (tentatively catalyzed by a Sn salt). 

Dusselier M, Van Wouwe P, de Clippel F, Dijkmans J, Gammon DW, Sels BF (2013) Mechanistic insight into the conversion of tetrose sugars to novel o-hydroxy acid platform molecules. ChemCatChem 5(2) 569-575... 

The simple sugars or monosaccharides are polyhydroxy aldehydes or ketones, and belong to Solubility Group II. They are termed tetroses, pentoses, hexoses. etc. according to the number of carbon atoms in the long chain constituting the molecule, and aldoses or ketoses if they are aldehydes or ketones. Most of the monosaccharides that occur in nature are pentoses and hexoses. 

The 3-deoxy pentose phosphates (44 and 45) can be further degraded to phosphorylated deoxy sugars (58) treatment of either of them with periodate will cleave the carbon-carbon bond between Ci and C2 to yield 2-deoxy-n- (46) and -L-gZycero-tetrose-4-phosphates (47). 

Derivatives of trioses, tetroses, and pentoses and of a seven-carbon sugar (sedohepmlose) are formed as meta-bohc intermediates in glycolysis and the pentose phosphate pathway. Pentoses are important in nucleotides. 

Another example of the ability of proteinogenic amino acids, small peptides, and amines to catalyse the formation of new C-C bonds has been demonstrated by Weber and Pizzarello they were able to carry out model reactions for the stereospecific synthesis of sugars (tetroses) using homochiral L-dipeptides. The authors achieved a D-enantiomeric excess (ee) of more than 80% using L-Val-L-Val as the peptide catalyst in sugar synthesis (in particular D-erythrose) via self-condensation of glycol aldehyde. 

It has been suggested15 that apiose [3-(hydroxymethyl)-D-g cero-tetrose] (LVII), a branched-chain pentose,47 originates from the aldol reaction of dihydroxyacetone with glycolaldehyde. The origin of this and all other branched-chain sugars so far encountered in natural products is uncertain, but they may arise from intermediate branched-chain carboxylic acids which are believed to be formed in the fixation of carbon dioxide (see above). 

Glyceraldehyde (2,3-dihydroxypropanal), acetol, and dihydroxyace-tone form 1-5% of biacetyl and a number of other products, including pyrocatechol and 33, after exposure to aqueous alkali at 300°. Such trioses as glyceraldehyde and dihydroxyacetone have been shown to form various hexoses by aldol reaction. Aldolization, followed by retro-aldoliza-tion, is undoubtedly a major consideration when three-, four-, and five-carbon sugars are subjected to elevated temperatures. Differences in thermolysis products, partially quantitative, are noticeable at 100°, but, at temperatures near 300°, it is quite difficult, if not impossible, to determine if the starting material was a triose, a tetrose, or a pentose. 

Aldose sugars make up a large part of the carbohydrate family, but the ones that are really worth knowing are part of the D-family. The simplest of these D-sugars is the triose glyceraldehyde. From there you have 2 tetroses, 4 pentoses, and 8 hexoses. Each of these aldose sugars has an enantiomer. 

Other sugars and polyols also complex with iron. Fructose is the most effective, but sorbitol, glucose, galactose, lactose, sucrose, pentoses and tetroses can also keep hydrolyzed ferric salts in solution. An excess of sugar must always be present in order to prevent ferric hydroxide precipitate. There appears to be a competition between the OH- and sugar hydroxyls for the Fe3+. 

The tetroses (four-carbon sugars) have not yet been studied crystal-lographically, undoubtedly due to the lack of suitable crystals. Handbooks list D- or L-erythrose as a colorless syrup, and D- or L-threose as very hygroscopic, colorless, microscopic needles. The X-ray diffraction patterns for erythritol13 and for several derivatives of D- or L-tartaric acid have been solved. 

In the first half of this century, only a few papers concerning the total synthesis of sugars (mostly DL-tetroses) were published. A substantial increase in the number of papers since 1950 was the consequence of many important developments in stereospecific functionalization of organic compounds, in separation techniques, and in methods for structural determination. 

The two aldotetroses, erythrose and threose, differ from the other aldoses in their behavior.23 Ring formation, to give furanoses, can occur only through the primary hydroxyl group, and is therefore less favored than with the higher sugars. Consequently, considerable proportions of the aldehydo and aldehydrol forms are found in solution. Like all a- and /J-hydroxyaldehydes, the aldehydo form of the aldotetroses readily forms dimers in concentrated solutions of the tetroses, the signals of the dimers are readily visible in their n.m.r. spectra. In the syrupy state, the tetroses consist mainly of dimers, rather than of furanoses they have never been crystallized. 

Hydroxymethyl- or Formyl-branched Sugars 3-C-(Hydroxymethyl)-D-g/ycero-tetrose (1)... 

The direct homologation technique was then extended to the synthesis of various uncommon carbohydrate structures. Thus, higher sugars of the L-series were obtained Starting from 2,3-0-isopropylidene-4-O-benzyl-L-threose (43) [39c] (Scheme 13), and the amino tetrose 47 and pentose 48 were prepared from the a-amino aldehyde 46 derived from L-serine [46a] (Scheme 14). These amino sugars were used as chiral building blocks for the... 

Some of the alditol acetates formed from deoxy sugars, pentoses, and tetroses are particularly volatile, and care should be taken when evaporating to dryness (see Basic Protocol 1, step 21). It is best to stop the evaporation as soon as the sample is dry. 

When there is a branch at C-3 in an aldose, the aldehydo form is hydrated to a much lesser extent than in an unbranched sugar the branching causes a 1,3-parallel interaction with one of the hydroxyl groups of the gem-diol. Whereas the ratio of aldehydrol to aldehyde is 10 1 for threose and 5 1 for erythrose, it is only 1.7 1 and 1.5 1, respectively, for their 3-C-methyl derivatives, and 0.4 1 for 3,3-dimethyl-DL-g/ym-o-tetrose.13... 

As indicated in Table 4.1, sugars can be further subclassified according to the number of carbons trioses, tetroses, pentoses, and... 

Monosaccharides, also called simple sugars, are classified by the number of carbon atoms (triose, tetrose, pentose, and so on) and by the nature of the carbonyl group (aldose or ketose). 

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