Synlett

Straightforward synthesis of quinazolinones having N-fused medium-sized ring urea was accomplished. Key intermediates were tert-butyl {2-[4-oxo-2-(4-oxopentyl)quinazolin-3(4H)-yl]ethyl}carbamates derived from copper-catalyzed domino reaction of tert-butyl [2-(2-iodobenzamido)ethyl]carbamates and cyclic enaminones. Steric hindrance of cyclic enaminones played an important role in the formation of quinazolinone ring. The eleven-membered ring urea moiety was readily achieved by direct cyclization using 1,1′-carbonyldiimidazole (CDI) of diamino intermediate generated by readily reductive amination and deprotection of tert-butyl {2-[4-oxo-2-(4-oxopentyl)quinazolin-3(4H)-yl]ethyl}carbamates.

A convergent total synthesis of 7-O-methylnigrosporolide and pestalotioprolide D has been accomplished in 17 linear steps and overall yields of 1.7% and 2.6%, respectively, starting from (S)-propylene oxide and (S)-benzyl glycidyl ether. Our synthesis exploited an acetylide addition and a Shiina macrolactonization to assemble the macrocycle, a Lindlar reduction, and Wittig and Still–Gennari olefinations to construct the three alkene groups, as well as a Jacobsen hydrolytic kinetic resolution to install the stereogenic center. The selection of the silyl protecting group of the C-4 alcohol was crucial for the final deprotection step. Our synthesis also led to a hypothesis that pestalotioprolide D might be an artifact of 7-O-methylnigrosporolide. The cytotoxic activities of the two synthetic compounds against six human cancer cell lines were evaluated. Synthetic pestalotioprolide D showed more potent cytotoxic activity than 7-O-methylnigrosporolide against all the cancer cell lines tested, and the SiHa cervical cancer cell line was the most sensitive to both synthetic compounds.

Decarboxylative transformations of paraconic acids, a class of γ-butyrolactones containing a carboxylic acid group at the β-position as their characteristic functionality, by using a combination of AgNO3/K2S2O8 were investigated. The dual function of AgNO3 as an initiator of the decarboxylation process and as a source of nitrogen dioxide radicals that react with aliphatic carboxylic substrates is reported for the first time. Starting from paraconic acids, β-nitro- and β-hydroxy γ-butyrolactones were obtained in good combined yields (41–85%) with moderate selectivity in a one-pot operation. The reactions were completed within an acceptable reaction time (two hours) under mild conditions that were tolerated by the γ-butyrolactone core. This study provides a direct and site-specific entry to β-nitro- and β-hydroxy γ-butyrolactones, which are important precursors in organic transformations.

A photoredox one-pot strategy for efficient accessing 3,4-dihydroquinolin-2(1H)-ones from anilines, oxalyl chloride, and electron-deficient alkenes is disclosed. The new approach features excellent synthetic efficiency, readily available starting materials, and simple operations. It is compatible with a variety of anilines and electron-deficient alkenes. A broad array of 3,4-dihydroquinolin-2(1H)-ones were prepared.

This paper describes the total syntheses of spirooliganones A and B, which provides control over the stereochemistry of the spiro center via a cascade reaction involving the in situ formation of an o-quinone methide and a hetero-Diels–Alder reaction.

An Ir/Ag dual-catalysis method has been developed for the synthesis of β-anti-substituted α-amino acids in high yields and with good enantioselectivities through a ligand/chelation-control strategy. By using this chiral-ligand-control strategy, a natural product for the regulation of a plant-growth hormone was synthesized on a gram scale in three steps.

Optically active amines represent critically important subunits in bioactive natural products and pharmaceuticals, as well as key scaffolds in chiral catalysts and ligands. Kinetic resolution of racemic amines and enantioselective desymmetrization of prochiral amines have proved to be efficient methods to access enantioenriched amines, especially when the racemic or prochiral amines were easy to prepare while the chiral ones are difficult to be accessed directly. In this Account, we systematically summarized the development of kinetic resolution and desymmetrization of amines through nonenzymatic asymmetric catalytic approaches in the last two decades.1 Introduction2 Kinetic Resolution of Amines2.1 Kinetic Resolution of Amines via Asymmetric Transformations of the Amino Group2.1.1 Asymmetric N-Acylations2.1.2 Asymmetric N-Alkylation2.1.3 Asymmetric N-Arylation2.1.4 Other Asymmetric N-Functionalizations2.1.5 Asymmetric Dehydrogenation of Amines2.1.6 Selective C–N Bond Cleavage of Amines2.2 Kinetic Resolution of Amines via Asymmetric Transformations without Amino Group Participating3 Enantioselective Desymmetrization of Amines3.1 Desymmetrization of Diamines3.2 Desymmetrization of Prochiral Monoamines4 Conclusion and Outlooks

We recently discovered a functional group tolerant and transition-metal-free conjunctive olefination reaction with applications in late-stage functionalization chemistry. In this Synpacts contribution, we analyze the conceptual background that has stimulated the discovery of this reactivity and reflect on the key aspects of its development.1 Introduction2 Conceptual Background2.1 Photoredox-Mediated Giese Reaction2.2 Photoredox Radical-Polar Reactivity3 The Development of the Process4 Conclusion

Synlett 2022; 33: 502-502DOI: 10.1055/s-0041-1737398Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents  |  Full text

Synlett 2022; 33: V-DOI: 10.1055/s-0041-1737399Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents