O-Cyanoethylidene Derivatives

Activation of trisaccharide cyanoethylidene derivative 118 with catalytic trityl perchlorate in the presence of a stiochiometric amount of the 3,6-di-O-trityl ether 119 afforded the tetrasaccharide 120 in 55% yield, whereas carrying out the same reaction with a half-molar equivalent of the bis trityl ether gave the heptasaccharide 121 in 60% yield (Scheme 21). 

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