Remarkable Switch of Regioselectivity in Diels–Alder Reaction: Divergent Total Synthesis of Borreverine, Caulindoles, and Flinderoles

Abstract

Switchable reaction patterns of dimerization of indole substituted butadienes via a Lewis acid and thermal activation are reported. While under acidic conditions dimerization occurred around the internal double bond of the dienophile, a complete switch of regioselectivity was observed under thermal conditions, where dimerization occurred around the terminal double bond of the dienophile. This switch of regioselectivity was further exploited for the divergent total synthesis of structurally diverse indole alkaloid natural products.

Oxidative Rearrangement of 2‐(2‐Aminobenzyl)furans: Synthesis of Functionalized Indoles and Carbazoles

“…The isolated caulindoles AÀ D could be accessed through the Diels-Alder reaction of corresponding (E)-5-(3-methylbuta-1,3-dien-1-yl)-1Hindoles. [12] We suggested that the obtained indole (E)-2 a could be smoothly converted into the corresponding diene, which should afford [4 + 2]-cyclodimers that can be considered as caulindoles analogues.…”

Enantiospecific Total Syntheses and Assignment of Absolute Configuration of Cannabinol‐Skeletal Carbazole Alkaloids Murrayamines‐O and ‐P

“…Also, there are few reports on enantioselective synthesis of these natural products either by chiral pool or asymmetric catalytic synthesis 9. With our ongoing interest in total synthesis10–12 of biologically active natural products,13, 14 herein we report the first enantiospecific total syntheses of murrayamine‐O ( 1 ) and murrayamine‐P ( 2 ) as well as their antipodes ent ‐ 1 and ent ‐ 2 , respectively, facilitated by Lewis acid catalyzed coupling of cyclic allylic alcohol 6 with carbazole derivative 7 for one pot CC and CO bond formation and a strategic effort to avoid the use of protecting group and expensive reagents.…”

Conformational Study and Vibrational Spectroscopic (FT-IR and FT-Raman) Analysis of an Alkaloid-Borreverine Derivative

“…In the present work, the borreverine derivative obtained two steps before the synthesis of borreverine was taken for investigation. 5 The novel chemical structure and vitally important biological activity of these alkaloids made it attractive for further investigation. In our previous report, 5 the synthesis of the borreverine derivative discussed in this work namely, ethyl 10-(3-(2-((ethoxycarbonyl)-amino) ethyl)-1-(phenylsulfonyl)-1H-indol-2-yl)-1,1,3-trimethyl-5-(phenyl sulfonyl)-2,4a,10,10a-tetrahydro-1H,5H-4b,9b-(epiminoethano)indeno [1,2-b]indole-13-carboxylate (abbreviated as BD thereafter), was already discussed along with the crystal structure.…”

“…5 The novel chemical structure and vitally important biological activity of these alkaloids made it attractive for further investigation. In our previous report, 5 the synthesis of the borreverine derivative discussed in this work namely, ethyl 10-(3-(2-((ethoxycarbonyl)-amino) ethyl)-1-(phenylsulfonyl)-1H-indol-2-yl)-1,1,3-trimethyl-5-(phenyl sulfonyl)-2,4a,10,10a-tetrahydro-1H,5H-4b,9b-(epiminoethano)indeno [1,2-b]indole-13-carboxylate (abbreviated as BD thereafter), was already discussed along with the crystal structure. In a continuation of our work, here we are interested in dealing with a conformational analysis of BD along with a vibrational spectroscopic investigation of the compound.…”