Synthesis of CH2-Linked Isomaltose via α-Selective Photoredox Vinyl C-Glycosylation.

C-Glycoside analogs of bioactive glycans and glycoconjugates are resistant to glycosidic hydrolysis and thus represent valuable scaffolds for drug discovery and chemical biology. We previously found that CH2-linked isomaltose (CH2-IM) exhibits potent amylase-inducing activity in Aspergillus nidulans compared to its native and linkage-edited counterparts. Here, we report a streamlined synthesis of CH2-IM via photoredox-catalyzed vinyl-C-glycosylation using N,N-dialkylbenzylamine derivatives as efficient halogen-atom transfer reagents. This approach enables concise access to CH2-IM and also facilitates the synthesis of 6'-modified analogs, providing a versatile platform for probing structure-activity relationships of IM derivatives. Notably, functionalization at the 6'- and anomeric positions completely abolishes the amylase induction activity.