Reductive Radical Cascades Triggered by Alkoxyl Radicals in the β-Cyclodextrin Framework

The generation and fate of 2I–VII,3I–VII,6II–VII-icosa-O-methyl-β-cyclomaltoheptaos-6I-O-yl radical under reductive conditions is described. Two radical cascade reactions are involved: the main one is triggered by a 1,8-HAT of the hydrogen at 5VIIC. The radical can reach the anomeric hydrogen at 1VC three sugar units ahead using a six-step sequence. The different hydrogen donor ability of the group 14 hydrides permits one to selectively stop the cascade at 5VIIC, 2VIC, and 4VIC to obtain β-CD with a β-l-Idop unit, acyclic hepta-, and hexa-saccharide structures, respectively.