Synthesis and anticancer studies of Michael adducts and Heck arylation products of sesquiterpene lactones, zaluzanin D and zaluzanin C from Vernonia arborea

Abstract

Sesquiterpene lactones containing α-methylene-γ-lactones, zaluzanin D 1 and zaluzanin C 2 were isolated from the leaves of Vernonia arborea.

Synthesis of Arylidene-β-lactams via exo-Selective Matsuda-Heck Arylation of Methylene-β-lactams

“…Under conditions that have previously been successfully applied to Heck reactions of electron-rich aryl iodides and αmethylene-γ-butyrolactones 35 or α-methylenesuccinimides, 22 we observed full conversion of 5a but very low yields of coupling product 7aa (entry 1). Presumably, heating the reaction mixtures at high temperatures over longer periods of time causes extensive decomposition of the β-lactam starting materials due to their high ring strain.…”

“…Aryl iodides, bromides, and triflates are the most commonly used electrophilic coupling partners in Mizoroki-Heck reactions. 34 Conditions that have been successfully used for the arylation of electron-deficient exomethylene heterocycles, e.g., α-methylene-γ-butyrolactones, involve Pd(OAc) 2 as a precatalyst, DMF as a solvent, and heating at elevated temperatures for up to 24 h. 35 In particular, electron-rich aryl halides often react slowly in Heck reactions and do not give the desired coupling products in acceptable yields. It has been shown that in these cases the addition of triortho-tolyl phosphine in a precatalyst-to-ligand ratio of 1:2 reliably accelerates the reaction and that the coupling products can be obtained in synthetically useful yields.…”

Iterative Arylation of Itaconimides with Diazonium Salts through Electrophilic Palladium Catalysis: Divergent β-H-Elimination Pathways in Repetitive Matsuda–Heck Reactions

“…Optimal reaction conditions for the coupling of these reagents with electrondeficient alkenes are known to differ significantly from the preferred conditions for arene diazonium salts, as can be seen from a recent comprehensive literature survey. 48 For these reasons, we did not include the optimized conditions for the Matsuda−Heck coupling of 5a and 6a (Table 1, entry 7) in this comparative investigation but chose previously established reaction conditions for the coupling of acyclic electrondeficient alkenes 48 and exo-methylene γ-lactones 49 with aryl halides and triflates as general guidance. Such conditions normally involve the use of dimethylformamide (DMF) as a solvent at elevated reaction temperatures, reaction times of several hours, triethylamine as a base, an excess of the electrophilic coupling partner, and very often activating phosphine ligands.…”

Botanical Exploration and Conservation in Pasir Banteng and Pasir Pogor, Gunung Gede Pangrango National Park

“…These flowers also have been utilized for aromatic therapy (Sujarwo and Arinasa 2014). Strobocalyx arborea or Vernonia arborea (synonym) is a potential plant used as an anti-inflammatory and anticancer (Sridharan et al 2016;Valkute et al 2018). Turpinia montana is a common plant used in Thailand as an anti-diarrheal medication (Grosvenor et al 1995).…”