Arabinose selective hydrolysis

As D-xylose and L-arabinose are 4-epimers, both, as well as mixtures of them (as provided by hemiceUulose), can be used to prepare enantiomerically pure synthetic intermediates the center C(4) of which is deoxy or sp -hybridized (alkenes, ketones). For instance, treatment of pure o-xylose with acetone under acidic conditions, followed by selective C(5) benzoylation, benzylation of the 3-alcoholic moiety, hydrolysis of the benzoate, and iodination furnishes the 5-iodo derivative... 

L-Arabinose reacts differently than o-xylose with acetone and gives a pyrano-side instead of a furanoside. Thus an alternative route to 18 was sought that can be applied both to o-xylose and L-arabinose [59]. It starts with the selective silylation of HO-C(5) [60], then acetonide formation protects alcohols moieties at C(l) and C(2). Subsequent benzylation of HO-C(3), hydrolysis of the silyl ether, and iodination provides 18 from o-xylose and 19 from L-arabinose (Scheme 7). Zinc reduction of 19 generates enal 20, but not the reduction of 18 [61]. Thus 18 and 19 are converted first into their methyl furanosides 22. The latter are reduced with Zn into... 

Hydrolysis of the saponin has afforded [352] glucose, arabinose, and two acidic aglycones acerotin (LXXVIIa) and acerocin (LXXVIIb). Acer saponin P has a therapeutic index of greater than two against W 256 and so has been selected for clinical study [351], It has been suggested that its activity may be associated with the two a, -unsaturated carboxyl groups [352],... 

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