Three new oxazoline alkaloids from Gymnotheca chinensis

Microwave-assisted rapid synthesis of chiral oxazolines

Chiral oxazoline compounds play an extremely important role in asymmetric synthesis and drug discovery. Herein a simpler, greener and more efficient microwave-assisted protocol to rapidly access chiral oxazolines is developed using aryl nitriles or cyano-containing compounds and chiral β-amino alcohols as starting materials. The reaction proceeds smoothly in the presence of a recoverable heterogeneous catalyst in either concentrated solution or under solvent-free conditions. The advantages of this method include rapidness, convenience, environmental protection, high atom economy, and excellent yields. The protocol should find wider application in the community in the future.

Application of chiral triazole-substituted iodoarenes in the enantioselective construction of spirooxazolines

A catalytic highly enantioselective synthesis of spirooxazolines is presented. Starting from readily available 2-naphthol-substituted benzamides and using catalytic amounts of a chiral triazole-substituted iodoarene catalyst, a variety of spirooxazolines can be isolated through an enantioselective oxidative dearomatization in up to 92% yield and 97% ee. The further synthetic utility of the optically enriched spirooxazolines was examined providing a corresponding 2-naphthalenole and an oxepin.

Synthesis of 2-Oxazolines from Ring Opening Isomerization of 3-Amido-2-Phenyl Azetidines

Chiral 2-oxazolines are valuable building blocks and famous ligands for asymmetric catalysis. The most common synthesis involves the reaction of an amino alcohol with a carboxylic acid. In this paper, an efficient synthesis of 2-oxazolines has been achieved via the stereospecific isomerization of 3-amido-2-phenyl azetidines. The reactions were studied in the presence of both Brønsted and Lewis acids, and Cu(OTf)₂ was found to be the most effective.

New pyrazinoquinazoline alkaloids Isolated from a culture of Stenotrophomonas maltophilia QB-77

Two new pyrazinoquinazoline alkaloids, epi-fiscalin D (1) and epi-fiscalin E (2), as well as three known analogues, norquinadoline A (3), quinadoline A (4), and fiscalin C (5), were isolated from ethyl acetate extract of the fermentation broth of Stentrophomonas maltophilia QB-77. The structures of new compounds were elucidated on the basis of extensive spectroscopic data analysis including UV, HRESIMS, and 1D and 2D NMR experiments. All the isolated compounds were tested for their in vitro cytotoxicity against five human cancer cell lines (SMMC-7721, MCF-7, HL-60, SW480, and A-549) and antibacterial activities against Bacillus subtilis, Escherichia coli, and Staphylococcus aureus.