Total Synthesis of Racemic Benzomalvin E, a Quinazolinone Isolated from Pencilium sp. FN070315 and Exploration to the Direct Synthesis of (E)-Benzomalvin B.

We present the first total synthesis of (±) benzomalvin E, featuring a quinazolino moiety with a 6-6-6-7-fused tetracyclic skeleton containing three nitrogen atoms. The key transformation involves Cu-catalyzed intramolecular C-N arylation of quinazolinone, leading to a sclerotigenin analogue that undergoes nucleophilic addition with benzaldehyde, enabling the synthesis of (±) benzomalvin E in six linear steps with a 33% overall yield. The (±) benzomalvin E's structure was validated by 2-D NMR and single crystal XRD analysis and was further transformed into (E)-benzomalvin B.

Potassium tert-Butoxide-Mediated Cascade Synthesis of Rutaecarpine Alkaloid Analogues: Access to Molecular Complexity on Multigram Scales.

In this study, we present a novel and cost-effective approach for synthesizing biologically significant analogues of rutaecarpine alkaloid through a one-step cascade reaction. The pentacyclic core of rutaecarpine alkaloid analogues is efficiently constructed using 2-aminobenzonitriles and substituted indole-2-carbaldehydes in the presence of the affordable base KOtBu. The salient feature of this approach is the promotion of a sequential cascade process within a single reaction vessel including the formation of a dihydroquinazolinone ring, oxidation, and cyclization. This method can be successfully applied on a larger scale, making it economically viable.

Diastereoselective reversible C-C bond exchange of oxindole-thiazolidienediones for dynamic combinatorial chemistry.

We herein describe a diastereoselective aldol exchange involving isatins and thiazolidinediones, providing oxindolyl-thiazolidienediones in aqueous media at pH 6. This equilibrium can also be achieved with oxindole exchange as well as cross-exchange within reasonable timescales. These metal and organic catalyst free reversible reactions provide a unique opportunity for the evolution of dynamic combinatorial libraries (DCLs) for target directed dynamic combinatorial chemistry (DCC) and system chemistry.

Potassium tert-Butoxide Promoted Synthesis of Dihydroquinazolinones.

We herein report an efficient synthetic protocol to access heterocyclic dihydroquinazolinones by a transition-metal-free process, involving the reaction of 2-aminobenzonitriles with aldehydes in the presence of KOtBu. The method is compatible with aromatic ketones providing 2,2-disubstituted dihydroquinazolinones in high yields. This reaction proceeds feasibly at room temperature and features a broad substrate scope and tolerance to a range of functional groups. The mechanism follows a radical pathway.