Alkaline degradation isolation

Chrysin (17) was the first flavone to be isolated in a pure form, and its stmcture was elucidated by identification of its alkaline degradation products (72—74). The stmcture was confirmed by synthesis (75,76). The same procedures were used to estabflsh the stmcture of other flavones and in so doing the foundation of flavone chemistry was laid (77). 

Xyloisosaccharinic acid [2,4-dihydroxy-2-(hydroxymethyl)butanoic acid] is one of the major, alkaline-degradation products of wood xylan, in particular, that of birch. The disaccharide, 2-O-D-xylopyranosyl-L-arabinose, which was isolated as a hydrolysis product of corn-cob hemicellulose, is readily degraded at 100° in 15 mM Ca(OH)2 to acidic products, primarily saccharinic acids. Xylan oligosaccharides from corn-cob hemicellulose produced 2,4-dihydroxy-2-(hydroxymethyl)buta-noic acid when exposed to 0.02 M Ca(OH)2 at 25°. However, it was noted that the xylan, itself, was stable at 100° in Af NaOH. The major acidic component of the hemicellulose fraction of slash pine Pinus el-liotti) after acid hydrolysis was identified as 4-O-methyl-D-glucuronic... 

The removal of the semicarbazide residue from aminochrome mono-semicarbazones by alkaline degradation has been reported.303 The resulting 6-hydroxyindole derivatives could be readily isolated as their methyl ethers.303... 

A main synthesis of o-hydroxydeoxybenzoins is the alkaline degradation (KOH-ethanol) of 3-aroylbenzofurans (152) the latter can thus be converted into 2-arylbenzofurans. The intermediate 3-formyl derivative (153) can be isolated (KOH-ethanol at room temperature, 22-24 hours) and is quickly converted into 154, with formation of H-COOH, b.y... 

Under alkaline conditions isolating lignin degradation products which are essentially of a phenyl.ethyl rather than a phenylpropyl nature is structurally important and requires a lignin structure by which the 7-carbon may be removed as a result of a 0-7 carbon-carbon cleavage reaction, either by direct alkaline hydrolysis or alkali-catalyzed hydrogenolysis. 

If the alkaline degradation and methylation of sinomenine is allowed to proceed for several weeks tetramethyl-bis-5 5 -sinomenol [xxxn, It = Me] (first thought to be a-tetramethoxyvinyldihydro-phenanthrene [17]) is obtained) and from the mother liquors, after oxidation, dimethylsinomenolquinone can be isolated [40],... 

Machell and Richards isolated S-deoxy-D-er /i ro-hexosulose from the alkaline degradation of 3-0-benzyI-D-glucose. The further transformations of the 3-deoxyhexosuloses by acids and alkali, and their significance in the browning reaction were also studied. Anet later reported the isolation of 3,4-unsaturated hexosuloses. 

Machell and Richards succeeded in isolating 3-deoxy-D-en/fkro-hexos-ulose (52), the postulated dicarbonyl intermediate in the formation of d-glucometasaccharinic acid (68) in the alkaline degradation of 3-0-sub-stituted D-glucose derivatives, from 3-0-benzyl-D-glucose (67). 

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