Intramolecular Metal-Free C(sp)-H Activation Enables a Selective Mono -Debenzylation of Fully Protected Aminosugars

Carbamate-bearing benzylated aminosugars undergo an I/I(III)-promoted intramolecular hydrogen atom transfer (IHAT) followed by a nucleophilic attack to provide polycyclic structures. Thus, suitably positioned benzyl ethers are surgically oxidized into the corresponding mixed /-benzylidene acetals, which can be conveniently deprotected under mild acidic conditions to grant access to selectively -deprotected aminosugars amenable for further derivatization. The scope of this strategy has been proven with a series of furanosic and pyranosic scaffolds. Preliminary mechanistic studies, including Hammett LFER and KIE analyses, support a reaction pathway with nucleophilic cyclization as the rate-determining step.