A Click-Chemistry Linked 2'3'-cGAMP Analog.

2'3'-cGAMP is an uncanonical cyclic dinucleotide where one A and one G base are connected via a 3'-5' and a unique 2'-5' linkage. The molecule is produced by the cyclase cGAS in response to cytosolic DNA binding. cGAMP activates STING and hence one of the most powerful pathways of innate immunity. cGAMP analogs with uncharged linkages that feature better cellular penetrability are currently highly desired. Here, we report the synthesis of a cGAMP analog with one amide and one triazole linkage. The molecule is best prepared via a first Cu(I) catalysed click reaction which establishes the triazole, while the cyclization is achieved by macrolactamization.