Advances and Strategies towards Synthesis of Aspidosperma Indole Alkaloids Goniomitine

Goniomitine is of the aspidosperma alkaloid family, with an angularly fused tetracyclic skeleton housing an all-carbon quaternary carbon chiral center alongside an aminal functional group. This natural product has garnered attention as a synthetic target due to its intriguing molecular architecture and anti-proliferative activity in recent years. Following the first synthesis of (-)-goniomitine by Takano in 1991, synthetic chemists have developed various methods. This review provides an overview of the methodologies used in the synthesis of goniomitine in racemic and enantiopure forms via divergent construction indole framework, indole functionalization, and the integrated oxidation/reduction/cyclization (iORC) sequence from 1991 to 2023.

Solvent-Mediated Tunable Regiodivergent C6- and N1-Alkylations of 2,3-Disubstituted Indoles with p-Quinone Methides

Indium-catalyzed, solvent-enabled regioselective C6- or N1-alkylations of 2,3-disubstituted indoles with para-quinone methides are developed under mild conditions. Notably, highly selective and switchable alkylations were selectively achieved by adjusting the reaction conditions. Moreover, scalability and further transformations of the alkylation products are demonstrated, and this operationally simple methodology is amenable to the late-stage C6-functionalization of the indomethacin drug. The reaction pathways were explained with the support of experimental and density functional theory studies.

Indane-1,3-Dione: From Synthetic Strategies to Applications

Indane-1,3-dione is a versatile building block used in numerous applications ranging from biosensing, bioactivity, bioimaging to electronics or photopolymerization. In this review, an overview of the different chemical reactions enabling access to this scaffold but also to the most common derivatives of indane-1,3-dione are presented. Parallel to this, the different applications in which indane-1,3-dione-based structures have been used are also presented, evidencing the versatility of this structure.

Rapid construction of indole-fused 8-10 membered lactones via a tandem reaction

An intramolecular anaerobic Mukaiyama hydration-initiated tandem reduction/condensation/acyl migration/aromatization reaction was developed, which enabled the rapid construction of indole-fused 8-10 membered lactones starting from cyclic 2-allyl-2-(2-nitrophenyl)-1,3-diketones. A nitro substituent in the substrates acted as both an oxygen source in the Mukaiyama hydration step and a nitrogen source in a tandem indole ring construction step. Our reaction features mild conditions, atom economy, and inexpensive reagents and it can be conveniently scaled up to a gram scale in modest yields. A rational reaction mechanism was also proposed based on previous reports and control experiments.

Facile synthesis of the spiro-pyridoindolone scaffold via a gold-catalysed intramolecular alkynol cyclisation/hydroindolylation

A simple approach for the synthesis of pyridoindolone scaffolds with a spiroannulated tetrahydrofuran ring is described. The overall process comprises intramolecular sequential gold-catalysed 5-endo-dig alkynol cycloisomerization and subsequent addition of indole C2 to the in situ generated oxocarbenium cation.

Transition Metal-Free, Methoxide-Catalyzed Synthesis of Pyridoindolones

A simple transition metal-free strategy for the synthesis of pyrido[1,2-a]indolone derivatives has been devised through sodium methoxide-catalyzed intramolecular cyclization of 2-alkenylated N-pyrimidyl indoles. The reactions involved a Smiles rearrangement/cyclization cascade, which resulted in a new series of N-fused indoles, potentially applicable skeletons in medicinal chemistry. This reaction presents simple eco-friendly reaction conditions, a high atom- and cost-economy, a short reaction time, and a broad range of substrate scope with high reaction efficiency.