Clinical Efficacy of Belotecan (CKD-602), Newly Developed Camptothecin Analog, in the 2nd Line Treatment of Relapsed Small Cell Lung Cancer

Novel Approach to the Construction of Fused Indolizine Scaffolds: Synthesis of Rosettacin and the Aromathecin Family of Compounds

Camptothecin-like compounds are actively employed as anticancer drugs in clinical treatments. The aromathecin family of compounds, which contains the same indazolidine core structure as the camptothecin family of compounds, is also expected to display promising anticancer activity. Therefore, the development of a suitable and scalable synthetic method of aromathecin synthesis is of great research interest. In this study, we report the development of a new synthetic approach for constructing the pentacyclic scaffold of the aromathecin family by forming the indolizidine moiety after synthesizing the isoquinolone moiety. Thermal cyclization of 2-alkynylbenzaldehyde oxime to the isoquinoline N-oxide, followed by a Reissert-Henze-type reaction, forms the key strategy in this isoquinolone synthesis. Under the optimum reaction conditions for the Reissert-Henze-type reaction step, microwave irradiation-assisted heating of the purified N-oxide in acetic anhydride at 50 °C reduced the formation of the 4-acetoxyisoquinoline byproduct to deliver the desired isoquinolone at a 73% yield after just 3.5 h. The eight-step sequence employed afforded rosettacin (simplest member of the aromathecin family) at a 23.8% overall yield. The synthesis of rosettacin analogs was achieved by applying the developed strategy and may be generally applicable to the production of other fused indolizidine compounds.

Transition Metal-Catalyzed C-H Activation/Annulation Approaches to Isoindolo[2,1-b]isoquinolin-5(7H)-ones

The isoindolo[2,1-b]isoquinolin-5(7H)-one scaffold is widely present in lots of bioactive natural products. Diverse types of strategies have been developed to construct this scaffold. Recently, transition metal-catalyzed C-H activation/annulation is emerging as a powerful and straightforward method to construct diverse polyheterocycles with high atom- and step-economy. It also has been employed for the synthesis of the isoindolo[2,1-b]isoquinolin-5(7H)-one scaffold. This review provides an introduction to recent advances for the preparation of isoindolo[2,1-b]isoquinolin-5(7H)-ones by using transition metal-catalyzed C-H activation/annulation. It will help researchers to find hidden opportunities and accelerate the discovery of novel transformations based on C-H activation/annulation.

Enantioselective rhodium-catalyzed addition of arylboronic acids to N-heteroaryl ketones: synthesis of α-hydroxy acids

The enantioselective addition of arylboronic acids to N-heteroaryl ketones provides a convenient access to chiral α-heteroaryl tertiary alcohols, yet addition reactions of this type have been challenging due to catalyst deactivation. In this report, an efficient rhodium-catalyzed addition of arylboronic acids to N-heteroaryl ketones is established, affording a variety of valuable α-heteroaryl alcohols with excellent functional group compatibility. The employment of the WingPhos ligand containing two anthryl groups is crucial for this transformation. In particular, a range of chiral benzoxazolyl-substituted tertiary alcohols were formed with excellent ee values and yields by employing a Rh loading as low as 0.3 mol%, which can serve as a practical protocol to furnish a series of chiral α-hydroxy acids after hydrolysis.

Maximizing Step-Normalized Increases in Molecular Complexity: Formal [4+2+2+2] Photoinduced Cyclization Cascade to Access Polyheterocycles Possessing Privileged Substructures

A new complexity building photoinduced cascade which amounts to an unprecedented formal [4+2+2+2] cycloaddition topology is developed to access complex nitrogen polyheterocycles. This photocascade is initiated by the excited state intramolecular proton transfer (ESIPT) in aromatic amino ketones with tethered dual unsaturated pendants, i.e. pyrrole and alkenic moieties, resulting in the formation of four σ-bonds and setting six new stereogenic centers in a single experimentally simple photochemical step with up to 220 mcbit complexity increases.

Recent advances in the chemistry of 2-chloroquinoline-3-carbaldehyde and related analogs

This review highlights the recently cited research data in the literature on the chemistry of 2-chloroquinoline-3-carbaldehyde and related analogs and their applications over the period from 2013 to 2017. It covers: synthesis of quinoline ring systems and reactions adopted to construct fused or binary quinoline-cord heterocyclic systems. The biological evaluation and the synthetic applications of the target compounds were illustrated.

Total Synthesis of Camptothecin and Related Natural Products by a Flexible Strategy

A flexible strategy for constructing natural products containing indolizinone or quinolizinone scaffolds and their analogues was developed, which was based on a cascade exo hydroamination followed by spontaneous lactamization. This method was applied in the total synthesis of camptothecin in nine steps in a new ring-forming approach. It was also used to efficiently prepare five biogenetically or structurally related natural alkaloids, including 22-hydroxyacuminatine, oxypalmatine, norketoyobyrine, naucleficine, and nauclefine, as well as 35 natural-product-like molecules. We believe that this method and the small-molecule library prepared with it can open new avenues for studying the bioactivity of camptothecin and Nauclea natural products.