Silver(I) oxide-mediated regioselective 2-monoacylation in 3-O-benzyl-α-l-rhamnopyranosides and application in synthesis of a protected tetrasaccharide fragment of potent cytotoxic saponins gleditsiosides C and D

The axial 2-hydroxyl group of methyl and allyl 3-O-benzyl-α-l-rhamnopyranosides was selectively acylated in 56–78% yields by reaction with 1.1 equiv of acyl chloride in the presence of 1.5 equiv of silver(I) oxide. Use of the method permitted a convenient synthesis of a protected tetrasaccharide fragment of triterpene saponins gleditsiosides C and D.

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