10.1021/jo015791h
The research describes a concise and stereocontrolled total synthesis of epothilone A and a formal synthesis of epothilone B, which are structurally unique polyketide macrolides with significant anticancer activity. The synthesis routes leverage nitrile oxide cycloadditions and a highly diastereoselective convergent aldol coupling, resulting in the expeditious construction of these complex molecules with complete stereocontrol. Key chemicals used in the process include isoxazolines, allylic alcohols, phosphonates, and various reagents for selective oxidations, reductions, and protection/deprotection steps. The study not only achieves the synthesis of epothilones A and B but also contributes to the advancement of novel methodologies for carbon-carbon bond formation and the development of scalable approaches to these important natural products.
10.1055/s-1996-4150
The study focuses on the synthesis of aliphatic 1,3-dinitro compounds, which can serve as precursors for various 1,3-difunctionalized compounds and heterocycles. The researchers developed a method to prepare these compounds by reacting primary aliphatic nitro compounds with primary or secondary α-nitroalkenes in the presence of catalytic amounts of triethylamine or potassium carbonate. The reactions were carried out at room temperature and yielded good results. The study also explored the reaction conditions and the yields and physical constants of the products. Additionally, the researchers investigated the instability of certain 2-aryl-1,3-dinitro compounds and the formation of by-products like isoxazolines and isoxazoles under specific conditions. The synthesized compounds were characterized using various spectroscopic techniques, and the structures of some compounds were confirmed through X-ray crystallography.
10.1021/ol900194v
The study explores an efficient method for converting aldoximes into nitrile oxides using iodobenzenediacetate (DIB) in methanol (MeOH) with a catalytic amount of trifluoroacetic acid (TFA). The nitrile oxides generated can be trapped in situ with olefins, leading to the formation of isoxazolines or isoxazoles, depending on the type of trap used. The study also investigates tandem oxidative processes, such as oxidative methoxylation or amidation of phenols, followed by intramolecular nitrile oxide cycloaddition (INOC), yielding synthetically valuable tricyclic intermediates. The findings demonstrate that DIB is an effective oxidant for aldoximes under these conditions, and the resulting intermediates hold potential for the synthesis of nitrogenous compounds.
10.1016/j.tetlet.2014.02.118
The study presents an environmentally benign method for synthesizing isoxazolines and isoxazoles via a cycloaddition reaction mediated by potassium chloride (KCl) in water. The key chemicals involved are aldoximes, which are oxidized to nitrile oxides by hypochlorous acid generated in situ from KCl and the oxidant Oxone?. These nitrile oxides then undergo a 1,3-dipolar cycloaddition with alkenes or alkynes to form the desired isoxazolines and isoxazoles. The process is optimized to achieve high yields and involves using KCl as a mediator, Oxone? as the oxidant, and water as the solvent, offering a green and efficient alternative to traditional methods.
