The emergence of terpene cyclization was critical to the evolutionary expansion of chemical diversity yet remains unexplored. Here we report the first discovery of an epistatic network of residues that controls the onset of terpene cyclization in Artemisia annua. We begin with amorpha-4,11-diene synthase (ADS) and (E)-β-farnesene synthase (BFS), a pair of terpene synthases that produce cyclic o...

The synthesis and cyclization of acyclic quinoxaline, pyridine, and pyrimidine enediynes (1-3) are described. These compounds were prepared using palladium(0) coupling of trimethylsilyl acetylene to o-dihaloor o-halotriflic heteroarenes. All compounds were prepared in modest to good yields. The enediynes prepared were shown to undergo Bergman cyclization. Kinetics over a minimum of 3 half-lives...

Peptides can serve as versatile cancer-targeting ligands and have been used for clinically relevant applications such as cancer imaging and therapy. A current and long-standing focus within peptide research is the creation of structurally constrained peptides generated through cyclization. Cyclization is envisioned to enhance the selective binding, uptake, potency and stability of linear precur...

In this work, an efficient synthesis of 3-hydroxy chromones was accomplished through oxidative cyclization mediated by lipase. This enzymatic process has salient features environmental friendliness, mild reaction condition, satisfactory yield, green reusable biocatalyst, and short time. The proposed method expands the application lipase in organic synthesis.

a general, simple, practical and convenient method has been described for the synthesis of anesthetic drug thiopental using thiourea in the presence of sodium ethoxide. anesthetic drug of thiopental was prepared in two stages; during the first stage, the alkylation of mthyl cyanoacetate was performed which was then to be followed by cyclization. alkylation of methyl cyanoacetate which was perfo...

Intramolecular nucleophilic and electrophilic cyclization of N-alkyne-substituted pyrrole esters is described. Efficient routes towards the synthesis of pyrrolopyrazinone, pyrrolotriazinone and pyrrolooxazinone have been developed. First, N-alkyne-substituted pyrrole ester derivatives were synthesized. Introduction of various substituents into the alkyne functionality was accomplished by a copp...

The cyclizations of two structurally similar 2-oxo-5-hexenyl-type radicals have been investigated by ab initio and density functional (UB3LYP/6-31+G**//UHF/6-31G* and UB3LYP/6-31G*//UB3LYP/6-31G*) calculations. The origin of apparently contradictory reports of 6-endo and 5-exo cyclizations is determined. Kinetic control favors 6-endo cyclization, while thermodynamic control gives 5-exo cyclizat...

1,2-Dialkynylimidazoles have been reported to undergo thermal cyclization/rearrangement to diradical and carbene intermediates. Optimization of the synthesis of the 1,2-dialkynylimidazole has provided sufficient material for kinetic and biological studies. The 1,2-dialkynylimidazole is cytotoxic against a wide range of cancer cells and induces apoptosis in A549 cells. Experimentally-determined ...

Radical cyclization reactions were performed by 5-exo-dig mode to yield cis-fused bicyclic systems, leading to the synthesis of bis-butyrolactone class of natural products. The study was aimed at understanding the impact of alkyl side chains of furanoside ring systems in L-ara configuration on the radical cyclization. It was amply demonstrated by experimental studies that the increase in the le...