Figure 2: Chemical structures of cyclic dinucleotide (CDN) STING agonists.
(A) Mammalian 2′3′-cGAMP. (B) Various naturally occurring or synthetic CDNs with the noncanonical 2′3′ linkage orientation that is produced by mammals. (C) Various naturally occurring CDNs with the canonical 3′3′ linkage orientation that is produced by bacteria. (D) Synthetic 2′2′-cGAMP with the noncanonical 2′2′ linkage orientation that has not yet been found in nature. (E) Naturally occurring 3′2′-cGAMP with the noncanonical 3′2′ linkage orientation that is produced by Drosophila melanogaster (i.e. fruit flies).