Carbocycloaddition Strategies for Troponoid Synthesis

Tropone is the prototypical aromatic 7-membered ring, and can be found in virtually any undergraduate textbook as a key example of non-benzenoid aromaticity. Aside from this important historical role, tropone is also of high interest as a uniquely reactive synthon in complex chemical synthesis as well as a valuable chemotype in drug design. More recently, there has been growing interest in the utility of tropones for catalysis and material science. Thus, synthetic strategies capable of synthesizing functional tropones are key to fully exploiting the potential of this aromatic ring system. Cycloaddition reactions are particularly powerful methods for constructing carbocycles, and these strategies in turn have proven to be powerful for generating troponoids. The following review article provides an overview of strategies for troponoids wherein the 7-membered carbocycle is generated through a cycloaddition reaction. Representative examples of each strategy are also provided.

Dihydroxyquingdainone Induces Apoptosis in Leukaemia and Lymphoma Cells via the Mitochondrial Pathway in a Bcl-2- and Caspase-3-Dependent Manner and Overcomes Resistance to Cytostatic Drugs In Vitro

Isatis tinctoria and its indigo dyes have already provided highly active anti-leukaemic lead compounds, with the focus mainly being on indirubin, whereas indigo itself is inactive. There are many more indigoids to find in this plant extract, for example, quingdainone, an indigoid derived from tryptanthrin. We present here a new synthesis of hitherto neglected substituted quingdainones, which is very necessary due to their poor solubility behaviour, and a structure-dependent anti-leukaemic activity study of a number of compounds. Substituted α-phenylaminoacrylic acid was synthesised by hydrogen sulfide extrusion from an analogue mercaptoacetic acid, available from the condensation of rhodanin and a substituted tryptanthrin. It is shown that just improving water solubility does not increase anti-leukaemic activity, since a quingdainone carboxylic acid is inactive compared to dihydroxyquingdainone. The most effective compound, dihydroxyquingdainone with an AC₅₀ of 7.5 µmole, is further characterised, revealing its ability to overcome multidrug resistance in leukaemia cells (Nalm-6/BeKa) with p-glycoprotein expression.

Colchicine Alkaloids and Synthetic Analogues: Current Progress and Perspectives

Colchicine, the main alkaloid of Colchicum autumnale, is one of the most famous natural molecules. Although colchicine belongs to the oldest drugs (in use since 1500 BC), its pharmacological potential as a lead structure is not yet fully exploited. This review is devoted to the synthesis and structure-activity relationships (SAR) of colchicine alkaloids and their analogues with modified A, B, and C rings, as well as hybrid compounds derived from colchicinoids including prodrugs, conjugates, and delivery systems. The systematization of a vast amount of information presented to date will create a paradigm for future studies of colchicinoids for neoplastic and various other diseases.

Progress and developments in the turbo Grignard reagent i-PrMgCl·LiCl: a ten-year journey

The structural and kinetic perspectives of i-PrMgCl·LiCl help to rationalize the trends of its unique reactivity and selectivity.