Figure 2. Structures of ladder-frame polyether prymnesins-1, -2, and -B1.

(A) Structure of prymnesin-1 and -2 first reported by Igarashi et al. [35], incorporating amended structural information by Sasaki et al. [38]. (B) Structure of prymnesin-B1 (notice the lack of rings H and I) recently reported by Rasmussen et al. [34], with areas of the backbone highlighted red that differ from prymnesin-1 and -2.