Biomimetic Synthesis of Moschamine-Related Indole Alkaloids via Iron-Catalyzed Selectively Oxidative Radical Coupling

Abstract

An iron-catalyzed oxidative radical coupling reaction was developed to selectively construct indolofuran or bisphenolic indole cores, which exist in two types of moschamine-related indole alkaloids. Both (+)-decursivine and 4,4″-bis(N-feruloyl)serotonin were biomimetically synthesized by using coupling reactions. The proposed reassignment of the structure of montamine as 4,4″-bis(N-feruloyl)serotonin was excluded.

Iron‐Catalyzed Oxidative C−C Cross‐Coupling Reaction of Tertiary Anilines with Hydroxyarenes by Using Air as Sole Oxidant**

“…The unsubstituted iron(II)-phthalocyanine complex (FePc) afforded the cross-coupling product 3a in 66 %y ield (entry 8), whereas other iron complexes led to either low yields of 3a (entries [9][10][11] or no product formation at all (entries [12][13][14][15][16][17]. The presentr esults confirmp revious findings that FePcF 16 has ah ighera ctivity compared to the parentc omplex FePc which is ascribed to the electronic effect of the fluorine atoms.…”

“…[3] Moreover,t he pre-functionalized substrates required for classical cross-couplingr eactions lead to al ow atom economy and the formation of by-products as unavoidable drawbacks.O xidative (or dehydrogenative) cross-couplingr eactions for CÀC bond formation by activation of two CÀHb onds are ah ighly useful synthetic alternative and represent ap erfect example of ag reen and economical chemical process. [4,5] However,m ost of the iron-catalyzedo xidativec oupling reactions requirep eroxides, [6][7][8] peracids, [9] or quinones [10] as stoichiometric oxidants to re-oxidize iron(II) to iron(III). Reactions using molecular oxygen or air as sole oxidanth ave rarely been explored.…”

“…[14] This reactionh as been applied to the homocoupling of diarylamines and 1-and 2-hydroxycarbazoles. [14,15] In contrastt om osto f the alternative iron-catalyzed oxidative cross-coupling reactions, [6][7][8][9][10] our procedure is using ambient air as sole oxidant.…”

Recent Advances of Transition Metal‐Mediated Oxidative Radical Reactions in Total Synthesis of Indole Alkaloids

“…[46] We commenced our synthesis from the preparation of compound 25 (Scheme 20). [46] We commenced our synthesis from the preparation of compound 25 (Scheme 20).…”

“…[46] Montamine was isolated from seeds of the ornamental plant Centaurea montana and showed significant anti-colon cancer activity in vitro (IC 50 ＝43.9 μmol/L). [46] Montamine was isolated from seeds of the ornamental plant Centaurea montana and showed significant anti-colon cancer activity in vitro (IC 50 ＝43.9 μmol/L).…”