Hydrogen fluoride solvolysis

Some glycosidic linkages have proved stable to hydrogen fluoride solvolysis. Attempts to isolate monosaccharides by solvolysis of the O-specific polysaccharide (13) of Shigella sonnet phase 1 with hydrogen fluoride and of the capsular polysaccharide (14) of Streptococcus pneumoniae type 1 failed. Prior acetylation of the free amino groups of the diamino sugar did not render the polymer susceptible to the solvolysis. 

Subjection of these polysaccharides to hydrogen fluoride solvolysis for 1S min at—23 ° gave a mixture of oligosaccharides from which could readily be purified a tetrasaccharide representing the backbone, one representing the sidechain, and a trisaccharide representing the side-chain minus the terminal D-galactosyl residue. The behavior of the pyruvic acetals on the... 

There seem to have been only two investigations on dediazoniations in a protic solvent, where the observed products indicate that, in addition to DN + AN solvolysis, an aryne is likely to be present as a metastable intermediate. Broxton and Bunnett (1979) have found that 3-nitroanisole is formed in the dediazoniation of 2-nitroben-zenediazonium ions in methanol in the presence of methoxide ions. This has to be interpreted as a product arising from 3-nitro-l,2-benzyne as an intermediate. The occurrence of the aryne mechanism in poly (hydrogen fluoride)-pyridine mixtures, as discovered by Olah and Welch (1975), is mentioned in Section 8.2. 

Benzhydrylamines are better suited than benzylamines as acid-labile linkers for amines. The MBHA linker ( methylbenzhydrylamine ), which is usually used to prepare peptide amides (see Section 3.3), can also be used as a linker for amines (Entry 1, Table 3.21). Hydrogen fluoride is, however, required as the cleavage reagent. Easier to cleave are alkoxy-substituted benzhydrylamines (Entries 2-5, Table 3.21), which can be prepared from the corresponding benzhydryl chlorides [263] or by reductive alkylation [410] or solvolysis [411] of the Rink amide linker. In the case of benzhydrylamines linked to polystyrene as benzyl ethers, treatment with TFA can lead to the release of the linker into solution (acidolysis of the benzylic C-O bond, see Figure 3.18). 

In most cases, the nonulosonic acids present in heteropolysaccharides could not be released as monosaccharides by direct acid hydrolysis because of their instability under the drastic conditions that were necessary to cleave the aldosidic linkage of the neighboring sugar residue. A combination of solvolysis with hydrogen fluoride and acid hydrolysis of the resulting... 

When the monosaccharide was not available directly after hydrolysis or solvolysis of the polysaccharide, a monomeric derivative for MS analysis could be obtained by a combination of chemical modifications and cleavages. Thus, in order to obtain an open-chain derivative of pseudaminic acid, OPS of S. boydii type 7 (Fig. 4, structure 12) was carboxyl-reduced, hydrolyzed under mild acid conditions, the products were carbonyl-reduced, solvolyzed with anhydrous hydrogen fluoride, and methylated.9,24... 

Rearrangement during solvolysis of the tosylate ofa 4-hydroxymethyl-4-methyl-3-oxo-steroid is discussed on p. 276. Simultaneous contraction and expansion of adjoining rings affords some curious products when cholesterol reacts with lead tetra-acetate and hydrogen fluoride (p. 258). The 12 ff-hydroxyconanine mesylate... 

The present article summarizes the data on application of hydrogen fluoride for structural analysis of polysaccharides, primarily those of bacterial origin. Some regularities in the stability of glycosidic linkages of different monosaccharides, and the mechanism of interaction between hydrogen fluoride and carbohydrates, are briefly discussed. The experimental technique for carrying out solvolysis is also described. 

Experiments showed that furan derivatives, which are frequently found to occur in the products of hydrolysis of pentose-containing polysaccharides with mineral acids, are not formed on solvolysis with hydrogen fluoride. ... 

Solvolysis with hydrogen fluoride was successfully employed to obtain partially methylated sugars in the methylation analysis of carbohydrates. 

Isolation of the alditol (23) on solvolysis with hydrogen fluoride of the methylated oligosaccharide fragment of P. aeruginosa L yi 0 10a O-spe-... 

Solvolysis of the polysaccharide (32) of P. aeruginosa L nyi 0 4a, 4c with hydrogen fluoride at room temperature led to the trisaccharide figment 33 as the only oligosaccharide product. 

By the solvolysis of N-tosyl-O-phenylhydroxylamine, prepared in 75-85% yield from phenoxylamine (Chap. 3) by reaction with 4-toluenesulphonyl chloride in pyridine, 4-fluorophenol resulted regiospecifically in 38% yield accompanied by an imino compound (34%) arising from the reagent which was used at ambient temperature and consisted of a solution of hydrogen fluoride in THF (5 1) (ref. 

Instead to have the galacto-conflguratlon. A new acidic amino-sugar, 2,3-dia,cetamido-2,3-dideoxy-L-guluronlc acid, has been identified as a component of the 0-specific polysaccharide of a Pseudomonas aeruginosa strain this polysaccharide, on solvolysis with hydrogen fluoride, released the trlsaccharlde repeating unit (1) in almost quantitative yield. l,5-Dldeoxy-l,5-imino-D-mannitol, a recently Isolated plant natural product (Vol. 13, p.78),... 

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