Concise Total Synthesis of (−)-Mersicarpine

A concise total synthesis of (−)-mersicarpine from a known cyclohexanone was accomplished. The azepinoindole core was constructed by a DIBAL-H-mediated reductive ring-expansion reaction of oxime

Three-Component Domino Process for the Pyrrolizine Skeleton via [3 + 2]-Cycloaddition–Enamine Cyclization Triggered by a Gold Catalyst

Pyrrolizines are bicyclic fused azaheterocycles with a bridgehead nitrogen contained in a core skeleton and are often found in biologically active compounds. Despite their importance, there have been few reports on concise and flexible syntheses of pyrrolizines. A novel one-pot, convergent method is described for pyrrolizines by simple mixing of iminoesters, acetylenes, and dipolarophiles in the presence of a cationic gold catalyst and an acid additive. This domino process affords multisubstituted pyrrolizines without handling unstable intermediates

Efficient Approach to 1,2-Diazepines via Formal Diazomethylene Insertion into the C–C bond of Cyclobutenones

Efficient monocyclic 1,2-diazepine formation via a tandem electrocyclization reaction of cyclobutenones with lithiodiazoacetate is demonstrated. The reaction proceeds through an oxy anion-accelerated 4π-ring opening of cyclobutene followed by an 8π-ring closure of the resultant oxy anion-substituted diazo-diene under mild conditions to furnish a 1,2-diazepine via formal diazomethylene insertion into the C–C bond of cyclobutenone

Autotandem Catalysis: Synthesis of Pyrroles by Gold-Catalyzed Cascade Reaction

A novel synthesis of substituted pyrroles by a gold­(I)-catalyzed cascade reaction has been developed. The reaction proceeded with an autotandem catalysis consisting of an initial addition of gold–acetylide to an acetal moiety and was followed by gold-catalyzed 5-<i>endo-dig</i> cyclization and aromatization. Gold catalysts play a dual role in activating nucleophilicity or electrophilicity of terminal acetylenes by forming gold–acetylides or by π-coordination. The formal (3 + 2) annulation of two components provided a variety of substituted pyrroles in a modular fashion

Synthesis of Denosomin–Vitamin D₃ Hybrids and Evaluation of Their Anti-Alzheimer’s Disease Activities

As an extension of previously conducted studies on developing an anti-Alzheimer’s disease agent, denosomin (1-deoxy-24-norsominone, an artificial inducer of neurite elongation), derivatives were designed and synthesized based on the hypothesis that our denosomin would exhibit axonal extension activity via a 1,25D₃-membrane-associated, rapid response steroid-binding protein (1,25D₃-MARRS) pathway. The biological assay revealed that the hybridization of characteristic δ-lactone in denosomin and the triene moiety in VD₃ was effective to enhance the nerve re-extension activity in amyloid β (Aβ)-damaged neurons