Tabernaesine J, a Novel Vincamine‐Type Indole Alkaloid with 6/5/6/6/6/5/5 Heptacyclic‐Ring System Scaffold from Tabernaemontana pachysiphon

Abstract

Tabernaesine J (1), an unprecedented vincamine-type indole alkaloid with 6/5/6/6/6/5/5 heptacyclic-ring system, as well as one new biogenetically related vincamine-type indole alkaloid (2), were isolated from leaves of Tabernaemontana pachysiphon. Their structures were established by a combination of HRESIMS, NMR, single crystal X-ray diffraction, and ECD calculation. The unprecedented penta-lactone ring in tabernaesine J (1) was postulated to be derived from acetyl-CoA enolate anion. Alkaloid 2 combined with fluconazole has the potential to overcome fluconazole resistance in Candida albicans.

Recent Advances in Domino Synthesis of Fused Polycyclic N‐Heterocycles Based on Intramolecular Alkyne Hydroamination under Copper Catalysis

“…Besides above methods, several other types of copper-catalyzed domino reactions based on intramolecular alkyne hydroamination have also been explored for the facile synthesis of fused polycyclic N-heterocycles. [61][62][64][65]67,69] In 2016, the Li and Liu group developed a domino cyclization of homopropargylic amines with imines for the preparation of fused pyrroloquinolines under Cu(II) catalysis (Scheme 30). [61] In the presence of Cu(OTf) 2 (5 mol%), the intramolecular hydroamination/Povarov reactions of N-aryl homo-propargylic amines with N-aryl imines furnished corresponding pyrroloquinoline derivatives in moderate to excellent yields.…”

“…In 2017, Zhan and coworkers developed an expeditious method for the synthesis of pyrazolo[5, 1-a]isoquinolines. [62] A broad spectrum of tricyclic N-heterocycles was generated via Cu(OTf) 2 -catalyzed four-step cascade bicycliazation reactions of N-propargylic sulfonylhydrazones (Scheme 31). The reactions proceeded smoothly under aerobic atmosphere and constructed tricyclic scaffolds from linear substrates through a four-step cascade sequence.…”

“…Numerous fused polycyclic indole alkaloids exhibit significant biological activities. [ 63 ] In 2017, Lu and Xiao et al . disclosed a domino divergent synthesis of a variety of polycyclic indole derivatives, including quinoline‐fused indolines and C(3a)‐indolyl furo/ pyrrolo indolines, by using two different classes of copper‐catalyzed cascade reactions between propargylic carbamates and indoles (Scheme 32).…”