Eight-membered rings with one oxygen atom

This chapter appears as a complement of the material and information previously published in Comprehensive Heterocyclic Chemistry II (CHEC-II)1 and CHEC-III,2 providing a privileged point of entry to the eight-membered ring oxygen heterocycle systems chemistry. Throughout the last decade, the numerous reviews on the synthesis of naturally occurring derivatives have highlighted the importance of this heterocycle moiety. Reviews describing the synthesis of brevetoxins (PbTxs) and ciguatoxins (CTXs),3 on the most recent developments on the synthesis of maitotoxin (MTX)4 and CTX,5 on the synthesis of brevetoxin A (PbTx-1) on the 1990s6 and on the isolation and synthesis of heliannuols, namely A, G, H, K, and L,7 have appeared. Nicolaou reviewed their work on the total synthesis of several natural compounds, including the synthesis of PbTx-1, which subunits B and G were obtained through lactonization and dithioketal cyclization reactions, respectively, and of brevetoxin B (PbTx-2), which subunit H was synthesized via hydroxyl dithioketal cyclization reaction.8 The synthesis of subunit H of PbTx-2 proposed by Nicolaou was also reviewed by T. Nakata.9