Asymmetric Total Synthesis of Bufospirostenin A

Abstract

The first and asymmetric total synthesis of bioactive bufospirostenin A, an unusual spirostanol with rearranged A/B rings, was accomplished. The synthetically challenging [5−7−6−5] tetracyclic ring system, found in bufospirostenin A and some other natural products, was efficiently constructed by the unique intramolecular rhodium-catalyzed Pauson−Khand reaction of an alkoxyallene-yne. The 11 stereocenters in the final product, including the 10 contiguous stereocenters, were installed diastereoselectively.

Dimeric Acylphloroglucinol Derivatives with New Skeletons from Leptospermum scoparium

“…Similarity, the triketones (norleptospermone or myrigalone A) went through an oxidation to form the intermediate ii , which could be coupled with 5,7‐dimethoxy‐8‐methylflavone or 5,7‐dimethoxy‐6‐methylflavone through Michael addition to provide 3 – 5 . Subsequently, compound 6 could be generated from 5 through 1,4‐reduction [24] . Then, the intramolecular nucleophilic reaction of 6 , followed by a methylation, could yield 2 .…”

Deciphering the Chameleonic Chemistry of Allenols: Breaking the Taboo of a Onetime Esoteric Functionality

“… 398 The first and asymmetric total synthesis of the bioactive bufospirostenin A, an unusual spirostanol natural product, has been accomplished taking advantage of the intramolecular allenic Pauson–Khand reaction of an alkyne-tethered allenol for the construction of a tetracyclic skeleton. 399 …”

“…More recent advances include the intramolecular (5 + 2) cycloaddition of allenol 705 for the synthesis of the tetracyclic core of Bufogargarizin C ( 707 ) (Scheme , reaction a), or the tandem Diels-Alder/carbonyl-ene reaction from allenol 708 to provide the Chloropupukeananin D analogous 710 (Scheme , reaction b) . The first and asymmetric total synthesis of the bioactive bufospirostenin A, an unusual spirostanol natural product, has been accomplished taking advantage of the intramolecular allenic Pauson–Khand reaction of an alkyne-tethered allenol for the construction of a tetracyclic skeleton …”

“…397 The first and asymmetric total synthesis of the bioactive bufospirostenin A, an unusual spirostanol natural product, has been accomplished taking advantage of the intramolecular allenic Pauson−Khand reaction of an alkynetethered allenol for the construction of a tetracyclic skeleton. 398 Jogyamicin ( 712) is an aminocyclopentitol-based natural product recently isolated from Streptomyces culture broth. Its potent antiprotozoal activity along with its challenging structure has attracted the interest of diverse research groups.…”

Concise Synthesis of 9,11-Secosteroids Pinnigorgiols B and E

“…Rearranged steroid natural products, including secosteroids (in which at least one ring is cleaved) and abeo -steroids (in which there is at least one migrated C–C bond within the classic tetracyclic framework), have recently received considerable attention from synthetic chemists owing to the structural diversity and biological importance of these compounds. , Representative naturally occurring rearranged steroids include cyclopamine, glaucogenins, cortistatins, − nakiterpiosin, strophasterol A, cyclocitrinols, − pleurocins, swinhoeisterol, bufospirostenin A, dankasterones, and periconiastone A. , Two particularly challenging examples of such natural products are the 9,11-secosteroids pinnigorgiol B ( 1 ) and pinnigorgiol E ( 2 ) (Figure ), − which possess a unique tricyclo­[5,2,1,1]­decane framework with an embedded γ-diketone moiety. These compounds were isolated by Sung and co-workers from a Pinnigorgia coral species in 2016, along with a biogenetic precursor, pinnisterol E ( 3 ) .…”