Arene oxides in biosynthesis. On the origin of crotepoxide, senepoxide, and pipoxide

Unusual metabolites from some Tanzanian indigenous plant species

“…U. purpurea [17]. Indeed, the occurrence in nature of the enantiomeric epoxides (-)-pipoxide (3) and (+)-pipoxide (4) facilitated confirmation of the biosynthetic proposal that was previously postulated for the formation of cyclohexane epoxides occurring in Uvaria species, based on the highly unstable arene oxide that would be formed from shikimic acid as the biosynthetic precursor [13,18,19] (Scheme 1). Since then, (-)-pipoxide has been isolated from another Tanzanian Uvaria species, viz.…”

“…It is interesting to note that the two sets of enantimeric pairs of cyclohexane epoxides 3 and 4, and 5 and 6 have already been isolated from Uvaria species [8,9,17,20,21], as previously predicted from the proposed biosynthesis of these compounds [13,18,19]. Thus, the biosynthetic proposal for polyoxygenated cyclohexane epoxides as shown in Scheme 1 envisions a nucleophilic β-arene oxide ring opening at C-3 through an α or β attack leading to di-oxygenated cyclohexadienes 7 and 8.…”

“…It has been postulated that the flavonoidal C-hydroxybenzyl group is biosynthetically derived from shikimic acid via the arene oxide shown in Scheme 1, followed by aromatization and deoxygenation [18].…”

Photooxygenation of a Microbial Arene Oxidation Product and Regioselective Kornblum–DeLaMare Rearrangement: Total Synthesis of Zeylenols and Zeylenones

“…In view of the isolation of polyoxygenated cyclohexenes in both enantiomeric series (as well as numerous epimeric natural products), the biosynthesis of this class of compounds has been the subject of much speculation. Ganem was the first to propose a biosynthetic pathway,24a involving an arene oxide intermediate 30 , possibly derived from isochorismic acid24b or from benzyl benzoate 1. Ring‐opening of this epoxide would give rise to cyclohexadiene trans ‐diol 31 .…”

Organocatalytic Asymmetric 1,6‐Addition Reactions

“…One year after White, Ganem and Holbert proposed that crotepoxides, along with the related families of pipoxides8 and senepoxides,9 do in fact originate from chorismate metabolism with the aforementioned arene oxide ( 15 ) as a natural intermediate 10. The proposed mechanism for epoxidation would involve singlet oxygen instead of reagents such as m CPBA.…”