D-Furanose

The name a-D-erythro-apiofuranose is ambiguous Chemical Abstracts Service (CAS) uses the trivial name D-apio-a-D-furanose Beilstein gives (3fl)-a-D-apio-furanose]... 

Online detection using 4H nuclear magnetic resonance (NMR) is a detection mode that has become increasingly practical. In a recent application, cell culture supernatant was monitored on-line with 1-dimensional NMR for trehalose, P-D-pyranose, P-D-furanose, succinate, acetate and uridine.33 In stopped-flow mode, column fractions can also be analyzed by 2-D NMR. Reaction products of the preparation of the neuromuscular blocking compound atracurium besylate were separated on chiral HPLC and detected by 4H NMR.34 Ten isomeric peaks were separated on a cellulose-based phase and identified by online NMR in stopped-flow mode. 

A Taste of Honey The fructose in honey is mainly in the jS-D-pyranose form. This is one of the sweetest carbohydrates known, about twice as sweet as glucose. The jS-D-furanose form of fructose is much less sweet. The sweetness of honey gradually decreases at a high temperature. Also, high-fructose corn syrup (a commercial product in which much of the glucose in corn syrup is converted to fructose) is used for sweetening cold but not hot drinks. What chemical property of fructose could account for both these observations ... 

Figure 4. Hydroxyl PMR signals (solvent, methyl sulfoxide-d6) for A) D-fructose after prior equilibration in water B) D-fructose at equilibrium in methyl sulfoxide-d6 C) leucrose, freshly dissolved crystals D) furanose, freslily dissolved crystals (arrows show the positions of signals that increase in intensity with time) G2-hydroxyl proton-2, F4-hydroxul proton-4 E) lactulose, freshly dissolved crystals. At the upper right are 13C-2 signals at 25.15 MHz for D-fructose in water (see Reference...

A taste of honey. Fructose in its P-d-pyranose form accounts for the powerful sweetness of honey. The P-d-furanose form, although sweet, is not as sweet as the pyranose form. The furanose form is the more stable form. Draw the two forms and explain why it may not always be wise to cook with honey. 

The above equilibria are confirmed by the complex, positive mutarotation in ethanol. First, a slow 3-D-furanose interconversion to equilibrium occurs, and then a very slow interconversion to equilibrium with the -D-pyranose form. The crystalline compound is, therefore, a /3-d anomer. This compound is interesting in that the identity of the forms taking part in the mutarotation can be ascertained, and the relative amounts of each determined, by nuclear magnetic resonance spectroscopy. Furthermore, the compound is unusual in existing in solution as the furanose forms, mostly. 

A, Methyl sulfoxide/D2O B, pyridine C, pyridine/DjO. a-F, /3-F, and a-P are lines assigned to the a-n-furanose, /3-D-furanose, and a-D-pyranose forms, respectively. The symbol s indicates a singlet the other lines are doublets. 

The /3-D-furanose modification of (84, R = H) is obtainable, in crystalline form, from acetone-ether. On reduction with sodium borohydride, followed by treatment with cation-exchange resin, it gives (after hydrolysis of the enol ether and an elimination /3 to the resulting carbonyl group) the acyclic form of iraws-3,4-dideoxy-D-grl2/cero-hex-3-enulose. Further reduction of this compound gives trans-S-hexene-D-ihreo-l, 2,5,Q-tetrol (see p. 128). 

The Haworth projection of a D-furanose is viewed edge on, with the ring oxygen away from the viewer. The anomeric carbon is on the right-hand side of the molecule, and the primary alcohol group is drawn up from the back left-hand corner. 

---