An Approach to the Core of Lactonamycin

Stereoselective Synthesis of Aromatic Polyketide Prealnumycin

Prealnumycin (1), a benzoisochromanequinone compound, produces biologically active exfoliamycin or alnumycin through hybridization with D-ribose or oxidation. We report herein a concise and stereoselective synthesis of 1. The anionic annulation of phthalide 5 with enone 6, prepared via a transition metal-catalyzed enantioselective route, afforded tricyclic lactone 4. This intermediate then underwent a highly diastereoselective introduction of an n-propyl group through nucleophilic addition followed by silane reduction. Subsequent regioselective arene oxidation of 18 using cerium(IV) ammonium nitrate (CAN) afforded naphthoquinone 2. Further manipulations, including acidic deprotection and elimination, yielded prealnumycin in 8 steps.

A Cyclobutanol Ring-Expansion Approach to Oxygenated Carbazoles: Total Synthesis of Glycoborine, Carbazomycin A and Carbazomycin B

The transition-metal-free total syntheses of the oxygenated carbazole natural products glycoborine, carbazomycin A and carbazomycin B are reported. The key step involves an NBS-mediated cyclobutanol ring expansion to 4-tetralones for the preparation of the tricyclic carbazole core.

Synthesis of Functionalized Isoindolinones via Calcium Catalyzed Generation and Trapping of N-Acyliminium Ions

Herein we report our full investigation into the calcium catalyzed generation and trapping of N-acyliminium ions from readily available 3-hydroxyisoindolinones. We have successfully employed a range of traditional nucleophiles including carbon, nitrogen, and sulfur containing reactive partners. The reaction is tolerant to a wide range of functionalities and provides high value scaffolds in good to excellent yields.