Herein, we report on the chemical synthesis of a tetrasaccharide precursor of the Treponema medium ATCC 700293. When the [2+2] glycosylation strategy could not be carried out due to the mismatch of donor-acceptor reactivities, we successfully completed the synthesis of the target tetrasaccharide precursor using a [3+1] glycosylation strategy.

Comprehensive Summary

Treponema is a Gram-negative anaerobic bacterium, among which the pathogenic Treponema can cause various diseases, such as venereal syphilis (Treponema pallidum), yaws (Treponema carateum), and oral diseases (Treponema denticola and Treponema medium). Although different from conventional lipopolysaccharides, the extracellular glycoconjugate of Treponema may still be a potential antigen and provide a candidate for vaccine development. Hence, we completed the first chemical synthesis of Treponema medium ATCC 700293 tetrasaccharide precursor containing L-ornithine (L-Orn) and D-aspartic acid (D-Asp) derivatives. The efficiency of non-reducing end disaccharide formation has been improved by optimizing the assembly of the protecting groups in the donors and acceptors. Our [3+1] glycosylation strategy attempted to reduce the length of the acceptor to increase the nucleophilicity of the hydroxyl group, thereby improving the efficiency of synthesizing the target tetrasaccharide. The L-Orn derivative was introduced at the final stage due to its influence on the glycosylation stereospecificity and efficiency. Therefore, the successful introduction of two amino acid derivatives and the synthesis of a tetrasaccharide precursor with complex functional-group modifications have provided valuable insights for synthesizing other complex bacterial glycans.

A convenient approach for the construction of 2-aminobenzothiazoles via I₂-catalyzed tandem cyclization reaction of amines and carbon disulfide has been developed.

Comprehensive Summary

A convenient approach for the construction of 2-aminobenzothiazoles via I₂-catalyzed tandem cyclization reaction of amines and carbon disulfide has been developed. The present approach starts from simple and readily available starting materials, affording a series of 2-aminobenzothiazoles in up to 89% yields under metal-free conditions. In this work, C—H/N—H functionalization was achieved and multiple C-hetero bonds were successfully constructed in one pot.

An asymmetric hydrosilylation of 2,2-difluoro-1,3-diketones was successfully realized by using a frustrated Lewis pair of chiral borane and tricyclohexylphosphine as a catalyst to give a variety of α,α-difluoro-β-hydroxyketones in high yields with up to 99% ee.

Comprehensive Summary

The asymmetric partial reduction of 1,3-diketones stands as a straightforward pathway to access optically active β-hydroxyketones. In this paper, an asymmetric Piers-type hydrosilylation of 2,2-difluoro-1,3-diketones was successfully realized by using a frustrated Lewis pair of chiral borane and tricyclohexylphosphine as a catalyst, delivering a variety of α,α-difluoro-β-hydroxyketones in high yields with up to 99% ee. Significantly, no over-reduced diol products were observed even with an excess amount of silanes. The product can be conveniently converted to α,α-difluoro-β-hydroxyester or 1,3-anti-diol via an oxidation with m-CPBA or a reduction with DIBAL-H without obvious loss of ee.

2-Aminobenzothiazoles derivatives have revealed a broad spectrum of biological activities, such as anti-HIV, anti-inflammatory, antioxidant, anti-microbial, anti-tumour, anti-infective, and anti-convulsant activities. A great amount of 2-aminobenzothiazole derivatives have been applied in drugs for the treatment of human diseases. A convenient approach for the construction of 2-aminobenzothiazoles via I₂-catalyzed tandem cyclization reaction of amines and carbon disulfide has been developed. More details are discussed in the article by Deng et al. on page 846—852.

2-Aminobenzothiazoles derivatives have revealed a broad spectrum of biological activities, such as anti-HIV, anti-inflammatory, antioxidant, anti-microbial, anti-tumour, anti-infective, and anti-convulsant activities. A great amount of 2-aminobenzothiazole derivatives have been applied in drugs for the treatment of human diseases. A convenient approach for the construction of 2-aminobenzothiazoles via I₂-catalyzed tandem cyclization reaction of amines and carbon disulfide has been developed. More details are discussed in the article by Deng et al. on page 846—852.

A Ni(II)-catalyzed asymmetric difunctionalization of alkynes is reported. This method involves intermolecular regioselective arylation of the alkynes and intramolecular desymmetrization of dinitriles, enabling the synthesis of enantioenriched azepine derivatives. The reaction exhibits good tolerance toward various functional groups, resulting in high yields and enantioselectivities.

Comprehensive Summary

The azepine ring is a prominent structural scaffold in biologically significant molecules. In this study, we present a Ni(II)-catalyzed asymmetric difunctionalization of alkynes, involving intermolecular regioselective arylation and intramolecular nitrile addition, enabling the synthesis of enantioenriched azepine derivatives. This reaction simultaneously installs an all-carbon quaternary stereocenter and introduces an unprotected imine functionality, showing great promise for subsequent transformations. The reaction exhibits good tolerance toward various functional groups, resulting in high yields and enantioselectivities. The synthetic utility of this methodology is further demonstrated through gram-scale synthesis and product derivatization. This research offers an efficient approach to the synthesis of seven-membered nitrogen heterocycles.

Palladium-catalyzed dipolar [4+2] and [6+2] cycloaddition reactions of benzo[d]isothiazole 1,1-dioxides (BDs) have been developed for the construction of of BD-fused 1,3-oxazinanes and 1,3-oxazocanes derivatives, respectively.

Comprehensive Summary

The Pd-catalyzed dipolar cycloaddition represents a significant synthetic strategy for the construction of useful heterocyclic compounds. This study developed the dipolar [4+2] and [6+2] cycloaddition reactions of benzo[d]isothiazole 1,1-dioxides (BDs) leading to the synthesis of BD-fused 1,3-oxazinane and 1,3-oxazocane derivatives, respectively. In particular, the synthesis of BD-fused 1,3-oxazinanes demonstrated regio- and enantioselective characteristics, resulting in products with good yields, enantioselectivity and regioselectivity (if applicable). Furthermore, the [6+2] cycloaddition reaction developed in this work represented the first strategy for the synthesis of medium-sized ring compounds based on BDs.

Azepine ring is a prominent structural scaffold in biologically significant molecules. This study demonstrates a Ni(II)-catalyzed alkyne functionalization/cyclization cascade reaction of alkyne-tethered malononitriles, involving intermolecular regioselective arylation of the alkynes and desymmetrizing addition onto the nitrile group, to access azepine derivatives. This strategy introduces an all-carbon quaternary stereocenter and an unprotected imine functionality simultaneously to the azepine scaffold, showing great promise for subsequent transformations. More details are discussed in the article by Liu et al. on page 873—878.

Azepine ring is a prominent structural scaffold in biologically significant molecules. This study demonstrates a Ni(II)-catalyzed alkyne functionalization/cyclization cascade reaction of alkyne-tethered malononitriles, involving intermolecular regioselective arylation of the alkynes and desymmetrizing addition onto the nitrile group, to access azepine derivatives. This strategy introduces an all-carbon quaternary stereocenter and an unprotected imine functionality simultaneously to the azepine scaffold, showing great promise for subsequent transformations. More details are discussed in the article by Liu et al. on page 873—878.

Comprehensive Summary

Eight rare capnosane-type cembranoids, sarcocinerenoids A—H (1—8) and two new cage-type cembranoids sarcocinerenoids I—J (9—10) were isolated from the soft coral Sarcophyton cinereum. The 5/11 bicyclic carbon skeleton is the same in Sarcocinerenoids A—H (1—8), and they collocate distinctive oxygen rings. Sarcocinerenoids I—J (9—10) with a cage-type structure have been discovered to have an oxygen bridge and an uncommon seven-membered ring. Extensive spectroscopic investigation, X-ray diffraction analysis, estimated ECD, and DP4+ probability assessments were used to ascertain the structures of the two types of diterpenoids. Moreover, compounds 1, 4 showed promoting angiogenesis activity in zebrafish assays.