Asymmetric Synthesis of α,β-Epoxy-γ-lactams through Tandem Darzens/Hemiaminalization Reaction

Enantioselective total synthesis of (+)-rubrobramide, (+)-talaramide A, and (-)-berkeleyamide D by a skeletal diversification strategy

A unified synthesis of (+)-rubrobramide, (+)-talaramide A, and (-)-berkeleyamide D was achieved from the vinylogous esters by a skeletal diversification strategy based on regioselective 5-exo or 6-endo cyclization. This report describes the first enantioselective total synthesis of (+)-rubrobramide and (+)-talaramide A. Additionally, synthetic spirocyclic lactam compounds, including (-)-berkeleyamide D, showed moderate inhibitory activity against amyloid-β aggregation for the potential treatment of Alzheimer's disease.

Chiral Lewis acid-bonded picolinaldehyde enables enantiodivergent carbonyl catalysis in the Mannich/condensation reaction of glycine ester

A new strategy of asymmetric carbonyl catalysis via a chiral Lewis acid-bonded aldehyde has been developed for the direct Mannich/condensation cascade reaction of glycine ester with aromatic aldimines. The co-catalytic system of 2-picolinaldehyde and chiral YbIII-N,N'-dioxides was identified to be efficient under mild conditions, providing a series of trisubstituted imidazolidines in moderate to good yields with high diastereo- and enantioselectivities. Enantiodivergent synthesis was achieved via changing the sub-structures of the chiral ligands. The reaction could be carried out in a three-component version involving glycine ester, aldehydes, and anilines with equally good results. Based on control experiments, the X-ray crystal structure study and theoretical calculations, a possible dual-activation mechanism and stereo-control modes were provided to elucidate carbonyl catalysis and enantiodivergence.

Pd-catalyzed amidation of 1,3-diketones with CO and azides via a nitrene intermediate

An efficient Pd-catalyzed amidation of 1,3-diketones has been developed using carbon monoxide and organic azides. This reaction provides a step-economic approach to produce β-ketoamides from readily available compounds under mild ligand-, oxidant-, and base-free conditions. The mechanistic studies showed that the reaction occurred through an in situ generated isocyanate intermediate.

Axially chiral hemiaminals from nonracemic α-amino acid derivatives (thiohydantoins): Synthesis and isomer identification

Stable, nonracemic axially chiral hemiaminals (O,N-hemiacetals) have been synthesized stereoselectively from lithium aluminum hydride (LiAlH₄ ) reductions of nonracemic 5-methyl- and 5-isopropyl-3-(o-aryl)-2-thioydantoins in tetrahydrofuran (THF) at room temperature in 10 min. Predominantly S-configured hemiaminals at C-4 of the heterocyclic ring were produced from the S-configured thiohydantoins at C-5 (by 80% when the C5 substituent is methyl and by 97% when it is isopropyl). The configuration at C-5 was retained during the reduction reaction. The stereochemical outcome of the axially chiral hemiaminals resulted from their conformational preferences.

Stereoselective assembly of 3,4-epoxypyrrolines via nucleophilic addition induced domino cyclization of 6-halo-1-oxa-4-azahexatrienes

A highly convergent assembly of 3,4-epoxypyrroline derivatives from azirines, diazo compounds and amines is developed based on the domino cyclization of 6-halo-1-oxa-4-azahexatrienes.

Total Synthesis of (-)-FD-838 and (-)-Cephalimysin A

We completed a nine-step total synthesis of (-)-FD-838 and (-)-cephalimysin A. Our synthesis features a biogenetically guided assembly of the highly oxidized spirocyclic core by Snider-type tandem epoxidations of the chiral substrate derived from an amino acid derivative. Our synthetic approach provides a general and versatile solution to access spirocyclic PKS-NRPS-based secondary fungal metabolites.