Nine new C9 polyketides, named aspiketolactonol (1), aspilactonols A–F (2–7), aspyronol (9) and epiaspinonediol (11), were isolated together with five known polyketides, (S)-2-(2′-hydroxyethyl)-4-methyl-γ-butyrolactone (8), dihydroaspyrone (10), aspinotriol A (12), aspinotriol B (1 3) and chaetoquadrin F (14), from the secondary metabolites of an Aspergillus sp. 16-02-1 that was isolated from a deep-sea sediment sample. Structures of the new compounds, including their absolute configurations, were determined by spectroscopic methods, especially the 2D NMR, circular dichroism (CD), Mo2-induced CD and Mosher’s 1H NMR analyses. Compound 8 was isolated from natural sources for the first time, and the possible biosynthetic pathways for 1–14 were also proposed and discussed. Compounds 1–14 inhibited human cancer cell lines, K562, HL-60, HeLa and BGC-823, to varying extents.
A practical approach to the direct α-methylation of 1,8-naphthyridines under mild reaction conditions has been developed using simple and readily available DMSO as a convenient and environmentally friendly carbon source.
By ruthenium/acid dual catalysis, we present, for the first time, a transfer hydrogenative para-selective aminoalkylation of aniline derivatives with N-heteroarenes. Position-2 of the sterically less-hindered pyridine ring of the N-heteroarenes couples with various aniline derivatives at the site para to the amino group, affording a wide array of structurally modified anilines, a class of highly valuable compounds with the potential for discovery and further creation of functional molecules. The developed chemistry features operational simplicity, a readily available catalyst system, excellent functional group tolerance, and exclusive regioselectivity, which offers a significant basis to access novel aniline derivatives that are currently inaccessible or challenging to prepare with conventional approaches, and design new coupling reactions via a hydrogen transfer strategy.
Semi-hydrogenation of alkynes is one of the most widely used methods for obtaining alkenes in laboratory preparation and in industry. Transition metal catalysts have been extensively studied for this transformation, but the tolerance of functional groups, such as pyridine, –OH, –NH2, –Bpin, and halides, and the toxicity of the trace amount of transition metal catalysts are still highly challenging. In this study, we report a general and robust strategy to achieve the semi-hydrogenation of alkynes using inexpensive and commercially available xanthate as the mediator. Mechanism studies support a non-radical process and H2O acts as the hydrogen donor.