Specific degradation of pectins via a carbodiimide-mediated Lossen rearrangement of methyl esterified galacturonic acid residues.
A specific, chemical degradation of the methyl esterified galacturonic acid residues of pectins is described. These residues are converted, with hydroxylamine, to hydroxamic acids, and then, with a carbodiimide, to isoureas; the latter undergo a Lossen rearrangement on alkaline hydrolysis. The isocyanates formed are hydrolysed to 5-aminoarabinopyranose derivatives, which spontaneously ring open to give 1,5-dialdehydes. The latter are reduced, in situ, to avoid peeling reactions, with sodium borohydride to give substituted arabitol residues. Thus, overall, partially esterified pectins are specifically cleaved to generate a series of oligogalacturonic acids bearing an arabitol residue as aglycone. Analysis of oligomers so generated discloses the pattern of contiguous nonesterification in a variety of pectins of differing degrees of esterification. Other potential applications are described.
Needs
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Nutrition, Health, and Consumer Science Division, Institute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4 7UA, UK. needsp@bbsrc.ac.uk
Rigby
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MacDougall
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D004951:Esterification; D005022:Ethyldimethylaminopropyl Carbodiimide; D006603:Hexuronic Acids / Q000737:chemistry; D006877:Hydroxamic Acids / Q000737:chemistry; D019811:Hydroxylamine; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D010368:Pectins / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
D006603:Hexuronic Acids; D006877:Hydroxamic Acids; D019811:Hydroxylamine; C007819:galacturonic acid; D010368:Pectins; D005022:Ethyldimethylaminopropyl Carbodiimide