Diastereoselective synthesis of 3,3-disubstituted 3-nitro-4-chromanone derivatives as potential antitumor agents

We report an efficient and highly diastereoselective protocol for the rapid construction of 3-nitro substituted 4-chromanones by an intramolecular Michael-type cyclization of α-nitro aryl ketones bearing unsaturated ester units.

Water-Tolerant Trifloaluminate Ionic Liquids: New and Unique Lewis Acidic Catalysts for the Synthesis of Chromane

The first example of triflometallate ionic liquids, named in analogy to chlorometallate ionic liquids, is reported. Trifloaluminate ionic liquids, synthesized from 1-alkyl-3-methylimidazolium triflates and aluminum triflate, were characterized by multinuclear NMR spectroscopy and FT-IR spectroscopy, revealing the existence of oligonuclear, multiply-charged trifloaluminate anions, with multiple bridging triflate modes. Acceptor numbers were determined to quantify their Lewis acidity, rendering trifloaluminate ionic liquids as medium-strength Lewis acids (AN = ca. 65). Used as acidic catalysts in the cycloaddition of 2,4-dimethylphenol and isoprene (molar ratio 2:1) to prepare chromane, trifloaluminate systems outperformed literature systems, showing high activity (conversions 94-99%, selectivities 80-89%) and at low loadings (0.2 mol%) at 35°C. Using these new systems as supported ionic liquid phase (SILP) on multi-walled carbon nanotubes (ionic liquid loading 16 wt%) delivered a recyclable catalytic system, with activity enhanced with respect to the homogenous regime.

Total synthesis of panicein A2

The first total synthesis of the unusual aromatic sesquiterpene panicein A₂ is reported and the structure of the natural product has been confirmed. When tested by the NCI against a range of human cancer cell lines, it was found that panicein A₂ exhibits very little antiproliferative activity at 10 μM – an observation that is at odds with the earlier report that stated panicein A₂ exhibits in vitro cytotoxicity against a number of tumour cell lines.

First syntheses of 2,2-dimethyl-7-(2'-methylbut-3'-en-2'-yl)-2H-chromen-6-ol and 2-(3'-methylbut-2'-enyl)-5-(2'-methylbut-3'-en-2'-yl)-1,4-benzoquinone, novel prenylated quinone derivatives from the New Zealand brown alga Perithalia capillaris

The first syntheses of 2,2-dimethyl-7-(2'-methylbut-3'-en-2'-yl)-2H-chromen-6-ol (1) and 2-(3'-methylbut-2'-enyl)-5-(2'-methylbut-3'-en-2'-yl)-1,4-benzoquinone (2), novel prenylated quinone derivatives from the New Zealand brown alga Perithalia capillaris, are reported, in which the key steps are consecutive Claisen rearrangements that proceed with both high chemo- and regioselectivity.

Novel Synthesis of Prenylated Phenols and Their Antioxidant Properties

A novel method for the prenylation of phenols has been developed using 2-methyl-but-3-ene-2-ol as the prenylating agent in the presence of Amberlyst 15. The prenylated catechols and quinols showed better antioxidant activity than the corresponding non-prenylated compounds in the in vitro DPPH and lipid peroxidation assay. The resorcinol derivatives did not show significant antioxidant activity.

A convenient and biogenetic type synthesis of few naturally occurring chromeno dihydrochalcones and their in vitro antileishmanial activity

2',2'-Dimethyl chromeno dihydrochalcones are very rare in nature as plant secondary metabolites. Recently we have reported three such compounds from the plant Crotalaria ramosissima. Chromeno dihydrochalcones contain a 2',2'-dimethyl benzopyran system, which are frequently encountered in many natural products and exhibit a variety of biological activities. We here report the strategy to conveniently synthesize naturally occurring chromeno dihydrochalcones by biogenetic type pyridine or Amberlyst-15 catalyzed chromenylation of dihydrochalcones and in vitro antileishmanial activity of chromeno dihydrochalcones and their intermediates.