Mannofuranoside reaction

The appearance of free iodine in periodate reaction-mixtures obviously indicates that the iodate formed is being further reduced,84 86 sometimes because of the addition of insufficient oxidant.86 87 This breakdown of iodate to free iodine has been reported as accompanying the a-hydrogen type of oxidation,89 at least as regards the oxidation of those methyl aldohexo-furanosides of which methyl a-D-mannofuranoside is a representative. The... 

It was found122 that 2,3 5,6-di-0-isopropylidene-D-mannose reacts with p-toluenesulfonyl chloride in pyridine, but the only product isolated was the corresponding mannofuranosylpyridinium p-toluenesulfonate. On the other hand, when 2 moles of the sodium salt of 2,3 5,6-di-0-iso-propylidene-D-mannose, dissolved in dry petroleum ether, were treated with one mole of p-toluenesulfonyl chloride, there apparently resulted the nonreducing-disaccharide derivative, 2,3 5,6-di-0-isopropylidene-D-mannofuranosyl 2,3 5,6-di-0-isopropylidene-D-mannofuranoside (a compound later prepared121 by condensation of 2,3 5,6-di-0-isopropylidene-D-mannosyl chloride with 2,3 5,6-di-0-isopropylidene-D-mannose). Presumably, the following reactions had taken place (Ip = isopropylidene) ... 

If p-toluenesulfonylation occurred under these conditions, the product distribution would depend on [R X]. Changing the concentration of p-toluenesulfonyl chloride from 0.10 M to 1.2 M did not affect the product ratio in a reaction with a dialkylstannylene acetal of methyl 2,3-0-isopropylidene-D-mannofuranoside. This result provides additional evidence that this reaction and all slower reactions occur under conditions where equilibration is faster than reaction. 

Nitrophenyl l-thio-P-o-mannopyranoside has been synthesized by reaction of acetochloromannose [207] or the mannosyl bromide 2 [202] with the sodium salt of 4-nitrothiophenol. A similar reaction between sodium thiophenoxide and aceto-bromomannose in HMPT gives phenyl 1-thio-P-D-mannopyranoside quantitatively [208]. In a related reaction the sodium salt of 1-thio-P-D-mannopyranose has been alkylated with benzyl bromide as in Schmidt s approach (Section 13.2.4) to give benzyl P-thiomannoside in 86% yield [209]. P-Linked 1-thiomannopyranosides can also be prepared by BFs-catalyzed anomerization of the readily available a-anomers [46]. The Lindberg protocol has also been used for the synthesis 1-thio-P-D-mannopyranosides [146, 149]. Aryl 1-thio-p-mannofuranosides have been syn-... 

The group of Sas developed a novel synthetic route to polyhydrojqrlated indolizi-dines (Scheme 8). Protected a-D-mannofuranoside 41 was transformed into derivative 43 by reaction with hydroiq lamine 42 (nitrone formation) followed by intramolecular 1,3-dipolar cycloaddition. This compound was transformed into ammonium salt 44, which was then cleaved under the basic conditions, giving the desired indolizidine scaffold 45. Alternatively, compound 43 was transformed into the mesyl ester 46, which cyclized upon treatment with K2CO3, providing the bicyclic compound 47. 

---