Total Synthesis of (±)-Nardoaristolone B and Its Analogues

Diastereoselective synthesis of α-dicarbonyl cyclopropanes via a lanthanide amide-catalysed reaction

Lanthanide bis(trimethylsilyl)amides, [(Me₃Si)₂N]₃Ln(μ-Cl)Li(THF)₃, were used as efficient catalysts for a one-pot reaction of α-ketoesters, dialkyl phosphite, and activated alkenes to produce α-dicarbonyl cyclopropanes in moderate to high yields. The reaction was stereoselective and the two adjacent carbonyls linked to the cyclopropane were in the cis-configuration. The high efficiency of the lanthanide amide in catalysing the reaction is the result of the cooperation between the lanthanide metal centre and the N(SiMe₃)₂ anion.

Access to Fused Tricyclic γ-Butyrolactones, A Natural Product-like Scaffold

Serendipitous findings of an acid mediated skeletal rearrangement of bicyclo-β-ketoester having cyclopropyl ring to access fused tricyclic γ-butyrolactones has been described. This novel transformation has been optimized to 30 mol% p-toluenesulfonic acid (p-TSA) in toluene using Dean-Stark apparatus, where the aldol condensation, cyclopropyl ring opening followed by cyclization took place in a single-pot operation. The resulting tricyclic compounds are interesting chemotype with natural product resemblance and may find useful applications in the future.

Methods Utilizing First-Row Transition Metals in Natural Product Total Synthesis

First-row transition-metal-mediated reactions constitute an important and growing area of research due to the low cost, low toxicity, and exceptional synthetic versatility of these metals. Currently, there is considerable effort to replace existing precious-metal-catalyzed reactions with first-row analogs. More importantly, there are a plethora of unique transformations mediated by first-row metals, which have no classical second- or third-row counterpart. Herein, the application of first-row metal-mediated methods to the total synthesis of natural products is discussed. This Review is intended to highlight strategic uses of these metals to realize efficient syntheses and highlight the future potential of these reagents and catalysts in organic synthesis.

Total Syntheses and Biological Evaluation of (±)-Botryosphaeridione, (±)-Pleodendione, 4-epi-Periconianone B, and Analogues

The total syntheses of (±)-botryosphaeridione, (±)-pleodendione, (±)-hoaensieremodione, 4-epi-periconianone B, and their analogues have been accomplished for the first time. All the synthesized target compounds were screened in neural anti-inflammatory assays using LPS induced microglia cells (N9). Among them, compounds 1 and 21 were identified as potential lead compounds for further profiling.

Enantioselective total synthesis of (-)-nardoaristolone B via a gold(I)-catalyzed oxidative cyclization

The first enantioselective total synthesis of (−)-nardoaristolone B is accomplished by the implementation of an enantio- and diastereoselective copper(I)-catalyzed conjugate addition/enolate trapping sequence and a gold(I)-catalyzed oxidative cyclization (intermolecular oxidant), employed for the first time in total synthesis.