Ipso substitution as a route to benzo[c]quinolizines and 4-hydroxycoumarins

Diastereoselective and E/Z-Selective Synthesis of Functionalized Quinolizine Scaffolds via the Dearomative Annulation of 2-Pyridylacetates with Nitroenynes

An organocatalytic Michael/aza-Michael cascade reaction was developed to build the functionalized quinolizine scaffolds in 60-82% yields, excellent diastereoselectivities, and E/Z selectivities. This protocol involves the [3 + 3] annulations of 2-pyridylacetates with nitroenynes through the dearomative strategy in the presence of an organic base under mild conditions. The versatile late-stage derivatizations further demonstrated the synthetic utility of this methodology.

Tandem aza-Michael addition-vinylogous aldol condensation: synthesis of N-bridged pyridine fused quinolones

Herein, we present a tandem aza-Michael addition-vinylogous aldol condensation strategy for the synthesis of N-bridged pyridine fused quinolone derivatives from quinolones and ynones. The presented tandem transformation features the construction of C-N and CC bonds in a single operation, under transition metal-free conditions. The wide substrate scope and gram scale synthesis of pyridine fused quinolone derivatives expand the synthetic value of the presented protocol.

Functionalized 4-hydroxy coumarins: novel synthesis, crystal structure and DFT calculations

A novel short-step methodology for the synthesis in good yields of functionalized coumarins has been developed starting from an activated precursor, the N-hydroxysuccinimide ester of O-acetylsalicylic acid. The procedure is based on a tandem C-acylation-cyclization process under mild reaction conditions. The structure of 3-methoxycarbonyl-4-hydroxy coumarin has been established by X-ray diffraction analysis and its geometry was compared with optimized parameters by means of DFT calculations.

IDENTIFICATION OF A NOVEL GLUTATHIONE ADDUCT OF DICLOFENAC, 4′-HYDROXY-2′-GLUTATHION-DESCHLORO-DICLOFENAC, UPON INCUBATION WITH HUMAN LIVER MICROSOMES

Clinical use of the nonsteroidal anti-inflammatory drug diclofenac (DF) is associated with an incidence of idiosyncratic hepatoxicity. The formation of reactive metabolites of DF in vivo has been proposed to be responsible for such toxicity. One type of reactive metabolite, a benzoquinone imine of DF formed through oxidation by cytochromes P450, can be trapped by glutathione in vitro in liver microsomes to form glutathione (GS) adducts. Three GS adducts from DF were reported in the literature, namely, 5-hydroxy (OH)-4-glutathione-DF, 4'-OH-3'-glutathione-DF and 5-OH-6-glutathione-DF, and they all have the same molecular weight of 616. Recently, we developed a sensitive and high throughput method for the detection of GS adducts from liver microsome incubation. This method uses a constant neutral loss scan of m/z 129, a "structure-characteristic" fragment for GS adduct, on an automated chip-based nanoelectrospray (Advion NanoMate 100) attached to a tandem mass spectrometer (Sciex API 3000). The analysis of GS adducts from human liver microsome incubation with DF by the NanoMate 100-API 3000 method unambiguously revealed a new adduct ion with m/z 583 (MH+), in addition to the known adduct peak with m/z 617 (MH+). This new adduct was further confirmed to be 4'-OH-2'-glutathion-deschloro-diclofenac by liquid chromatography (LC) tandem mass spectrometry (MS), LC/MS-NMR, and comparison to a synthetic standard.