D-Mannose, 2,5-anhydro

Fusion of an oxirane ring to a pyranose ring also deforms it, and thereby lowers its stability. The composition of 2,3-anhydro-D-mannose in aqueous solution,165 as determined by g.l.c. of the trimethylsilyl derivatives, is 23 7 65 5. This is remarkably similar to the composition of a solution of 2,3-O-isopropylidene-L-rhamnose. For 2,3-anhydro-D-allose, the ratios are166 41 12 5 42 (or 41 5 12 42). In this case, although the proportion of furanose forms is substantial, there is no clear preponderance of the //-furanose form, presumably because OH-1 and OH-2 are trans but OH-1 is quasi-equatorial by contrast, in the (preponderant)... 

When compared with those in other Tables, the data in Table VII show that Perlin s conclusions are generally valid. 2,3-Anhydro-D-mannose and 2-C-(hydroxymethyl)-D-ribose (hamamelose) are exceptions there is actually somewhat less furanose in their solutions in dimethyl sulfoxide and pyridine, respectively, than in water but these can hardly be regarded as typical sugars. 

J. G. Buchanan and D. M. Clode, Synthesis and properties of 2,3-anhydro-D-mannose and 3,4-anhydro-D-altrose, J. Chem. Soc., Perkin Trans. 1, (1974) 388-394. 

Fig. 2. Topographies of hexameric non-glucose cyclooligosaccharides composed of D-mannose (83), D-allose (84) and 2,3-anhydro-D-mannose units (55) in an a-(l—>4)-link-up each.

Lemieux and Fraser-Reid174 have reported that the reaction of methyl 3,4,6-tri-0-acetyl-2-deoxy-2-iodo-j3-D-glucopyranoside (137) with bromine and silver acetate in acetic acid containing potassium acetate gives an almost quantitative yield of 1,3,4,6-tetra-O-acetyl-2,5-anhydro-D-mannose methyl hemiacetal (139), obtained as an... 

Migration of the ring-oxygen atom also occurred predominantly in the deamination of the tetra-O-acetyl derivatives of 2-amino-2-deoxy-a- and -/3-D-glucopyranose to give 3,4,6-tri-0-acetyl-2,5-anhydro-D-mannose (10), which is unstable and readily eliminates acetic acid to... 

Studies have revealed that the deamination of 2-amino-2-deoxy-D-glucosides is more complicated than previously supposed. It has been reported that methyl 2-amino-2-deoxy-a- and -/3-d-glucopyranoside give, in addition to 2,5-anhydro-D-mannose, methyl 2-deoxy-2-C-formyl-a- and -/S-D-ribofuranoside (for example, 97 to 98) in yields of 25 and 19%, respectively, under the experi-... 

Pictet-Spengler reaction of 2,5-anhydro-D-mannose (55) and tryptamine hydrochloride (56) at ambient temperature affected the tetrahydropyri-dine ring formation of the (li ) and (15)-l-(a-D-arabinofuranosyl)-l,2,3,4-tetrahydro-/3-carboline 57 [830C2721, 83JCS(CC)601] (Scheme 18). 

Whereas methyl 2-amlno-2-deoxy-oi-D-glucopyranoside with sodium nitrite in anhydrous acetic acid gave mainly the 2,5-anhydro-D-mannose derivative (68), the 0-tetra- -acetate of the same sugar and 2,3,4,6-tetra-0-acetyl-3-D-glucopyranosylamine gave mainly the... 

Deoxy-sugars. Part XXV. Structure and Reactivity of Anhydro-sugars. Part II. Derivatives of 3 6-Anhydro-D-mannose, 3 6-Anhydro-2-deoxy-D-galactose, and 3 6-Anhydro-2-deoxy-D-g ucose," A. B. Foster, W. G. Overend, M. Stacey, and G. Vaughan,/. Chem. Soc., (1954) 3367-3377. 

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