2- hexuloses

A second category of six carbon carbohydrates called 2-hexuloses has the constitution shown How many stereoisomeric 2 hexuloses are possible ... 

Similar to DHAP aldolases, the 3-hexulose 6-phosphate aldolase found in Methylomonas Ml 5 is highly specific for the aldol donor component D-ribulose 5-phosphate, but accepts a wide variety of aldehydes as replacement for formaldehyde as the acceptor. With propanal,... 

R)-2-Hydroxy-3-thiopropanal (Table 5), which could not be isolated from the reaction mixture, can be directly converted into 6-thio-D-wnimo-2-hexulose (7%) and 6-thio-L-xylo-2-hexulose (93 %) via rabbit muscle aldolase catalyzed condensation with dihydroxyacetonephos-phate28. 

Note. In Chemical Abstracts Service (CAS) usage the locant for the carbonyl group precedes the stem name, e.g. 3-hexulose. 

Dihexulose dianhydrides are intermolecular cyclic acetals formed by the condensation of two hexulose molecules with the elimination of two water molecules, and the formation of two linkages involving the 2- and one other position of each component. They are named4 by placing the word dianhydride after the names of the two parent monosaccharides. The order of precedence for these... 

The taste properties of various other ketoses, including 2-pentuloses, 2-hexuloses, and 2-octuloses, have also been studied (see Table XV) to determine the significance of the 2-hydroxyl-2-hydroxymethyl arrangement of 2-ketopyranoses. Some of these, for example, a-D-tagatose (25), -d-g/uco-2-heptulose (26), a-D-mnMno-2-heptulose (27), a-D-fa/o-2-heptulose (28), a-D-a/tro-2-heptulose (29), and D-g/ycero-a-D-g/ co-2-octulose (30),... 

Meyerhof and Schulz86 studied this reaction in trisodium phosphate solution, and regarded it as coming to a triose-hexose equilibrium containing 92 % of hexose. Berl and Feazel67 examined the kinetics of hexose formation from trioses in alkaline solution, and noted that 75-90% of hexulose is formed from DL-glycerose alone, but that the yield is lower (about 60%) when dihydroxyacetone is added in equivalent quantity. Paper chromatog-... 

Escherichia coli, adapted to grow on L-rhamnose, will convert this sugar to 6-deoxy-L-am6mo-hexulose ( L-rhamnoketose ). In the presence of ATP, dialyzed aqueous extracts of these cells will phosphorylate this... 

Treatment of 3-deoxy-l,2 5,6-di-0-isopropylidene-a-D-erythro-hex-3-enofuranose with iodine and thallous fluoride in anhydrous ether afforded227 3-deoxy-l-fluoro-3-iodo-l,2 5,6-di-0-isopropyli-dene-D-xy/o-4-hexulose in 80% yield, together with small proportions of (tentatively identified) 3-deoxy-4-fluoro-3-iodo-l,2 5,6-di-0-iso-propylidene-a-D-allofuranose and two unidentified products. A mechanism proposed for the furanose ring-opening involves the formation of a 3,4-iodonium ion, and attack by fluoride at C-l. 

The carbonyl group in glucose and ribose is an aldehyde such compounds are termed aldoses. Fructose, by contrast, has a ketone group and is therefore classified as a ketose. Glucose could also be termed an aldohexose and fructose a ketohexose, whereas ribose would be an aldopentose, names which indicate both the number of carbons and the nature of the carbonyl group. Another aspeet of nomenclature is the use of the suffix -ulose to indicate a ketose. Fructose could thus be referred to as a hexulose, though we are more likely to see this suffix in the names of specific sugars, e.g. ribulose is a ketose isomer of the aldose ribose. 

Recorded as o-allulose but preferred name is D-psicose or D-ri6o-2-hexulose. 

---