Pyranoses synthesis

Pyrano[4,3-6]pyran-2,5-dione, 7-methyl-aromaticity, 3, 639 Pyranopyrandiones aromaticity, 3, 639 dipole moments, 3, 627 synthesis, 3, 795 tautomerism, 3, 644 Pyranopyranones molecular structure, 3, 624 Pyranopyrans synthesis, 3, 760, 784 Pyranopyrazoles synthesis, 5, 321, 330 Pyranopyrazolones synthesis, 5, 334 Pyranopyridine synthesis, 3, 834 Pyranoses... 

Koenigs-Knorr reaction of, 990 molecular model of, 119, 126, 985 mutarotation of, 985-986 pentnacetyl ester of, 988 pentamethyl ether of, 988 pyranose form of, 984-985 pyruvate from. 1143-1150 reaction with acetic anhydride, 988 reaction with ATP, 1129 reaction with iodomethane, 988 sweetness of. 1005 Williamson ether synthesis with. 988... 

Sulfinylacrylate 41 has been successfully used in the enantioselective synthesis of pseudo-sugar [46, 47]. Cycloaddition of (S)-3-(2-pyridylsulfinylacrylate) (41) with furan and 3,4-dibenzyloxyfuran under Et2AlCl catalysis afforded cycloadducts 42, 43 and 44 (Equation 3.12) which were converted into pseudo-manno-pyranoses 45, 46 and 47 (Figure 3.5). 

P212121 Z = 4 D = 2.01 R = 0.04 for 1,611 intensities. The compound is a minor product in the synthesis of methyl tyveloside. The pyranose conformation is a distorted 4, with Q = 66 pm 6= 162° (p=H8a. The (methylthio)carbonyl side-chain is extended. The C-S bond-lengths are 174.8, 179.1 pm. The C-I bond-length is 215.2 pm. The absolute configuration was confirmed by using the anomalous-scattering factors of the iodine atoms. 

A number of derivatives of D-glucuronic acid have been made by Goebel and Babers37 with a view to their use in the synthesis of aldobionic acids. With the same object Owen, Peat and Jones38 prepared both pyranose and furanose derivatives of D-glucurone. 

A similar approach had been described for the synthesis of the mycotoxin patulin (2,3-pyranose-fused unsaturated lactone) from a 2-arabinopyranos-2-uloside derivative,16 and more recently, for the synthesis of a potent germination stimulant and some analogous compounds from D-xylose or commercially available D-glucuronic acid y-lactone.17... 

Synthesis from exo-glycals. Several routes to C-l glycals from 1-exo-methylene pyranoses and furanoses have been described recently. 

The enzymatic synthesis of sucrose also throws light on the formation of the furanose form of fructose in the sucrose molecule. The fact that sucrose is directly formed from D-glucose-l-phosphate and D-fructose supports Isbell and Pigman s34 and Gottschalk s85 evidence that the latter monosaccharide occurs in solution in an equilibrium mixture of furanose and pyranose forms. This makes it unnecessary to postulate a special mechanism of stabilization of a five membered (furanose) ring before the formation of compound sugars containing the D-fructose molecule.86... 

NMR is predictive of reactivity within a series Within a set of common donors (i.e., galactose) in which the C2 position is constant, the H chemical shift of the anomeric carbon appears to be a good predictor of relative reactivity. Little correlation is found when the C2 position is varied, or between different donor pyranoses. The extent to which this correlation will prove useful remains in question. We envision that its primary applicability may be in trouble shooting a failed synthesis when a complex donor does not behave as predicted. Checking the H NMR of the advanced intermediate may quickly reveal that the RRV value for the pyranose of interest is not as expected, and hence the reactivity is not as expected. 

Liu, J. and Wong C.-H., Aldolase-catalyzed asymmetric synthesis of novel pyranose syn-thons as a new entry to heterocycles and epothilones. Angew. Chem. Int. Ed., 2002, 41, 1404-1407. 

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