Weermann and Lossen Rearrangements

Selective cleavage of the 2-acetamido-2-deoxyaldosidic linkage in peracetylated benzyl 2-acetamido-2-deoxy-4-0-/3-D-galactopyranosyI-/3-D-glucoside by treatment with ferric chloride, to afford the corresponding oxazoline, has been reported.180 

Further examples of modified Smith degradation, in which the polyalcohol is methylated prior to hydrolysis under mild conditions, uronic acid degradation, and /3-elimination preceded by oxidation have been reported in connection with structural studies on the Klebsiella type 28 (Ref. 182), 57 (Ref. 183), 59 (Ref. 142), and 81 (Ref. 184) capsular polysaccharides. 

The /3-elimination reaction with esterified uronie acid residues has been performed by using the nonionic base 1,5-diazabicyclo [5.4.0]-undec-5-ene185 plus acetic anhydride in benzene.186 By performing the reaction under acetylating conditions, eventual further degradation, as already discussed, is prevented. 

Interaction of Galactomannans with Carrageenan, Agar, and Other Polysaccharides. 284 

Galactomannans have attracted considerable academic and industrial attention because of the central role they play in the area of polysaccharide interactions. On cooling even concentrated solutions 

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The cleavage of polysaccharides by hydrolysis with acid, by oxidation with periodate or chromium trioxide, by base-catalysed jS-elimination, by deamination, and by Weermann and Lossen rearrangements has been ably reviewed. A new approach to selective cleavage of the glycosidic bond to the reducing-end residue of oligosaccharides has involved base-catalysed j8-elimination on a model 5-deoxy-5-nitromaltitol derivative. ... 

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