Laureoxolane, a new bromo ether from

Biosynthesis of the C15-acetogenin laurepoxide may involve bromine-induced skeletal rearrangement of a Δ4-oxocene precursor

“…In an elegent series of studies, Fukuzawa and Murai showed that haloether deacetyllaurencin, upon exposure to lactoperoxidase, halide and hydrogen peroxide, was transformed into a diverse array of other natural products including laureoxanyne, laurefucin, and notoryne (Scheme 1a). 2–4 These findings are strongly suggestive of the existence of key transient bromonium species 1 , which can undergo an intramolecular bromoetherification and subsequent oxonium ylide-induced reactions to yield the observe products (Scheme 1a). Structural variants bromofucin 5 and chlorofucin 6 are also believed to be accessed via analogous bromonium intermediates.…”

“…Less well understood is the biosynthesis of epoxy tetrahydrofuran natural products 2 such as laurepoxide 11 (Figure 1). Murai has shown that lactoperoxidase is capable of catalyzing the formation of 5-membered bromoethers from linear polyenes (Scheme 1b).…”

Stereoselective Halogenation in Natural Product Synthesis

“…However, upon treatment of 232 with N ‐bromosuccinimide, unexpected bromocyclization of the ether oxygen triggered a rearrangement to give a bromotetrahydrofuran containing a pendant epoxide ( 234 ) as a single diastereomer, instead of 233 . This type of epoxyfuranyl scaffold can also be found in a related natural product, laureoxolane ( 236 ) . Another brominative rearrangement was observed while attempting a derivatization of 234 .…”

“…This type of epoxyfuranyl scaffold can also be found in ar elated natural product, laureoxolane (236). [86] Another brominative rearrangement was observed while attempting aderivatization of 234.Instead of the S N 2bromination of the secondary alcohol on the tetrahydrofuran ring, the activated alcohol was displaced by the epoxide to form an oxonium species,w hich was opened by bromide ion to give a trans-fused bicycle 235,w hich has af used bistetrahydrofuran motif that is structurally related to kumausallene (27)a nd aplysiallene (36).…”

Stereoselektive Halogenierungen in der Naturstoffsynthese

“…Bei der Behandlung von 232 mit N ‐Bromsuccinimid wurde jedoch nicht die Verbindung 233 gebildet, vielmehr löste die unerwartete Bromcyclisierung des Ethersauerstoffs eine Umlagerung zu einem diastereomerenreinen Bromtetrahydrofuran mit einem anhängenden Epoxid ( 234 ) aus. Dieses Epoxyfuranylgerüst ist auch in dem verwandten Naturstoff Laureoxolan ( 236 ) vorzufinden . Eine weitere bromierende Umlagerung wurde in Versuchen zur Derivatisierung von 234 beobachtet.…”