Studies Directed towards the Synthesis of the Acridone Family of Natural Products: Total Synthesis of Acronycines and Atalaphyllidines

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.

K2CO3-Catalyzed Dual C-C-Coupled Cyclization to 3-Amino-4-benzoylbiphenyls and In Situ I2-Catalyzed C-N Bond Forming Annulation: A Metal-Free Synthesis of Arylacridones

Unprecedented metal-free cyclization catalysis reactions are developed in a highly regioselective fashion to synthesize 3-amino-4-benzoyl biphenyls and arylacridones with high atom economy. Catalytic K2CO3 is utilized as the only reagent for the unusual rapid dual C-C-coupled cyclization between β-keto enamines and cinnamaldehydes to furnish the functionalized biphenyls. Its C(sp2)-H functionalized C-N bond-forming cyclization was performed in situ using molecular I2 as a catalyst to furnish valuable arylacridones. Plausible mechanisms for the new cyclization reactions are predicted by conducting various control experiments and ESI-MS analyses.

Synthesis and characterization of alkaloid derived hydrazones and their metal (II) complexes

Alkaloids have been known overtime to have medicinal uses. Exploring alkaloid derived hydrazones and their complexes as potential therapeutic agents with a view to improving the medicinal uses of alkaloids are imperative. 1,8-dichloroacridone hydrazone hydrochloride, 1-chloro pilocarpine nitrate-3-chlorophenyl hydrazone and 1-phenethyl-4-piperidone formyl hydrazone ligands were synthesized via Wolff–Kishner condensation reaction. Five metal (II) complexes of cobalt, nickel and manganese were prepared by stirring the ligands with the respective metal salts. The ligands and complexes were characterized using elemental analyses, molar conductivity, FTIR, 1H and 13C nmr, UV–Vis spectra, melting point and solubility. Antimicrobial activities of the ligands and their complexes were tested against four bacteria (Staphylococcus aureus, Streptococcus faecalis Escherichia coli, Salmonella paratyphimurium) and a fungus (Candida albican). The molar conductance values indicate that they are 1:1 and 1:2 type electrolytes while the elemental analyses of the complexes reveals a 1:1 metal to ligand stoichiometry. The relevant IR bands suggest coordination is through the C=N, C=O, N=C–O and C–N groups. Both 1H and 13C nmr corroborated the elemental analysis while the UV–Vis reveals intra-ligand charge transfer while the complexes exhibited the expected metal transitions bands. A proposed octahedral geometry is supported by spectral data. Only 1, 8-dichloroacridonehydrazone hydrochloride ligand was found to be active against all the organisms. Cobalt and nickel complexes of 1,8-dichloroacridonehydrazone hydrochloride were active against S. paratyphimurium and S. aureus, respectively, while cobalt complex of 1-chloropilocarpinenitrate-3-chlorophenylhydrazone was active against S. faecalis and S. paratyphimurium. The minimum inhibitory concentrations (MIC) were also recorded.