Dimeric Erythrina Alkaloids from the Flower of Erythrina variegata

Abstract

Unprecedented dimeric Erythrina alkaloids, spirocyclic (6/5/6/6) erythrivarine A (1) and spiro-fused (6/5/7/6) rings erythrivarine B (2), were isolated from the cultivated plant, E. variegata. The structures were determined on the basis of 1D and 2D NMR, FTIR, UV, and mass spectroscopic data and X-ray crystal diffraction. The biogenetic relationship of 1 and 2 is proposed.

Cobalt(II)‐Catalyzed [5+2] C−H Annulation of o‐Arylanilines with Alkynes: An Expedient Route to Dibenzo‐[b,d]azepines

“…Dibenzo[ b , d ]azepines are a valuable class of medium‐sized N ‐heterocycles, widely found in the core structures of many natural products and bioactive compounds. For example (Figure ), erythrivaeine B, one of dimeric Erythrina alkaloids, was isolated from the cultivated plant, E. variegata . LY‐411575 has proved to be an effective g‐secretase inhibitor for the treatment of melanoma and Alzheimer's disease .…”

Highly Regio‐, Diastereo‐, and Enantioselective Synthesis of Tetrahydroazepines and Benzo[b]oxepines through Palladium‐Catalyzed [4+3] Cycloaddition Reactions

“…[1] Among them, sevenmembered ring systems containing heteroatoms are key structural motifs in many natural products and bioactive compounds. [2] Unfavorable entropy effects and transannular interactions make it more challenging to access these ring systems.D espite extensive efforts in the development of various strategies for accessing medium-sized rings,including ring isomerization, ring expansion, and rearrangement, the discovery of more efficient and versatile routes is still highly desired.…”

Selectivity in Ring‐Closing Metathesis: Synthesis of Propellanes and Angular Aza‐tricycles

“…[5] For example, synthesis of cis-syn-cis triquinane [6] over the propellanes, [7] tandem ring-closing metathesis (RCM) [8] followed by aromatization, chemo-selective self-metathesis [9] and crossmetathesis (CM) reactions. The propellanes [11] and angular aza-tricycles are generally found as core structural units in biologically active natural products [12] (Figure 1) such as kopsia indole alkaloids (e. g., fruticosine and kopsanone) [13] and erythrina alkaloids [14] (e. g., isococculidine and b-erythrodine). Fischer indolization and Grignard reactions are used as key steps to prepare the substrates required for RCM.…”

“…Fischer indolization and Grignard reactions are used as key steps to prepare the substrates required for RCM. The propellanes [11] and angular aza-tricycles are generally found as core structural units in biologically active natural products [12] (Figure 1) such as kopsia indole alkaloids (e. g., fruticosine and kopsanone) [13] and erythrina alkaloids [14] (e. g., isococculidine and b-erythrodine). [15] More specifically, this method is applicable for the synthesis of compounds containing quaternary carbon centers, present in several naturally occurring alkaloids ( Figure 1).…”