Six-membered rings, sugars

The simple piperidine pelletierine from Punica granatum (pomegranate) (Punicaceae) and Duboisia myoporoides (Solanaceae) is an anthelmintic. The simple piperidine derivatives deoxy-mannojirimycin (DMJ) and deoxynojirimycin (DNJ) from Lonchocarpus species (Fabaceae) are glycosidase inhibitors because they are structurally similar to the pyranose (six-membered ring) sugar moieties of the glycosidase disaccharide substrates. 

Six-membered-ring sugars are pyranoses five-membered-ring sugars are furanoses. 

Sucrose is made from joining glucose, a six-membered ring sugar (left), to fructose, a five-membered ring sugar (right)... 

DOMINO REACTIONS TOWARD BUTENOLIDES FUSED TO SIX-MEMBERED RING SUGARS AND TfflO SUGARS... 

The well-known reaction leading to ring expansion of cyclic ketones has been applied to derivatives of oxo sugars in an attempt to develop a new route to novel deoxy sugars. By treatment with diazomethane both a five-membered (42) and a six-membered (26) sugar ring have been expanded by insertion of a methylene group. 

Peaks at m/e 113 and 85 have been found in the mass spectra (12) of other O-isopropylidene ketals of sugars, as well as in Figure 7. Since these shift to m/e 119 and to m/e 88 and 91 in the mass spectrum of 10a as they did for the d6-analogs in Reference 12, the structures, 17, 18, and 19 from Reference 12 are shown as possible explanations. The peak at m/e 85 (91) could alternatively be from m/e 113 (119) by loss of carbon monoxide (28 mass units) from the six-membered-ring of structure 17b. 

Galactose, a sugar related to glucose, contains a six-membered ring in which all the substituents except the -OH group indicated below in red are equatorial. Draw galactose In its more stable chair conformation. 

Pyranose (Section 25.5) The six-membered-ring form of a simple sugar. 

The structures of the a-D-aldo-pento and -hexo-pyranose monosaccharides are shown in Pig. 1. In all cases, these sugars will be studied as the six-membered-ring tautomer, as shown. 

C13-0065. The five-carbon sugar ribose can form a six-membered ring, ribop Tanose, that differs from... 

The reactivity of carbohydrates is dominated by the reactivity of the aldehyde group and the hydroxyl on its next-neighbor (/ ) carbon. As illustrated by the middle row of Fig. 2.3, the aldehyde can be isomerized to the corresponding enol or be converted into its hydrate (or hemiketal) form upon reaction with water (or with an hydroxyl-group). These two reactions are responsible for the easy cycliza-tion of sugars in five- and six-membered rings (furanose and pyranose) and their isomerization between various enantiomeric forms and between aldehyde- and ketone-type sugars (aldose and ketose). 

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