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Lipopolysaccharides (LPSs) are major virulence determinants in Gram-negative bacteria and are responsible for many pathophysiological processes during bacterial infections. However, the accessibility of LPS-associated oligosaccharides for infectious mechanism study and vaccine development remains challenging. We report an efficient stereocontrolled approach for the synthesis of a common inner-core trisaccharide containing difficult-to-access, rare, higher-carbon sugars: a heptose (Hep) and 3-deoxy-α-d-manno-oct-2-ulosonic acid (Kdo). Key features include comprehensive elaboration of a practical synthesis of versatile Hep and Kdo building blocks, and stereoselective assembly of an inner-core trisaccharide from multiple pathogenic bacteria.

Herein, we report the novel strategy for the synthesis of 4-enamino-5-phenyl-2,3-dihydroisothiazole 1-oxides (in other words α-phenyl β-enamino γ-sultims) based on the CSIC reaction. Particularly, readily available α-amino nitriles (the Strecker products) reacted with benzyl sulfinyl chloride to give the corresponding sulfinamides, which upon treatment with excess of LiHMDS converted into the target α-phenyl β-enamino γ-sultims. The method works well and tolerates strained 3- and 4-membered spirocyclic substituents. A preliminary in silico study indicated that the γ-sultim scaffold can be considered a promising pharmacophore template.

A visible-light-catalyzed arylcarboxylation of allenes with CO₂ was developed using [Ir(ppy)₂(dtbbpy)]PF₆ (ppy = 2-phenylpyridine; dtbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine) as a photocatalyst to synthesis β-aryl β,γ-unsaturated carboxylic acids. This multicomponent protocol proceeds in an atom-economical way with exclusive regioselectivity. Preliminary mechanistic experiments suggested that allylic carbanion species are the key intermediates.

An expedient and easy-to-handle synthetic platform has been established for the constructing of 2H-thiophenes carrying fluorine atoms through [4+1] cyclization of enaminothiones with fluorinated carbene precursors. This simple reaction system is well compatible with a wide range of substrates under completely metal-free conditions. The resulting 2H-thiophenes can undergo further late-stage modifications to yield a wide range of fluorine-substituted heterocycles.

Herein, we present a rapid and efficient method for synthesizing cyclic acetals and ketals utilizing a rotary evaporator. Unlike the conventional Dean–Stark dehydration process, which typically demands extended reaction times and copious amounts of organic solvents, our approach affords the synthesis of cyclic acetals and ketals with varying ring sizes in 30 min while using minimal quantities of dimethyl sulfoxide as the solvent. This innovative protocol features high yields, fast reactions, easy operation, and broad substrate applicability.

We report a unique synthetic route to benzo[7]annulene derivatives. When benzylidene malonates having a 1-(N,N-dialkylamino)alkyl group at the ortho-position are treated with a stoichiometric amount of M(OTf)₃ (M = Sc, Yb, Gd), three transformations ([1,4]-hydride shift/isomerization into an enamine/intramolecular Stork enamine acylation) proceed sequentially to afford various benzo[7]annulene derivatives in moderate chemical yields. To our knowledge, the present reaction is the first example of an internal redox reaction involving a [1,n]-hydride shift/(n+3)-cyclization process.

Palladium-catalyzed asymmetric [3+2] cycloaddition reaction of vinyl cyclopropane and electron-deficient dienes was realized. The cycloaddition reaction proceeded regioselectively on the distant C=C double bond of electron-deficient dienes, and was mainly controlled by the steric hindrance of the 5-substituent of electron-deficient dienes. Chiral multi-substituted cyclopentanes bearing three functional groups (monosubstituted alkene, conjugated ester, and cyano) and three continuous stereocenters were obtained in moderate to high yields, diastereoselectivities, and enantioselectivities.

Heteroatom-based olefinating reagents (e.g., organic phosphonates, sulfonates, etc.) are used to transform carbonyl compounds into alkenes, and their mechanism of action involves aldol-type addition, cyclization, and fragmentation of four-membered ring intermediates. We have developed an analogous process using ethyl 1,1,1,3,3,3-hexafluoroisopropyl methylmalonate, which converts electrophilic aryl aldehydes into α-methylcinnamates in up to 70% yield. The reaction plausibly proceeds through the formation of β-lactone that spontaneously decarboxylates under the reaction conditions. The results shed light on the Knoevenagel–Doebner olefination, for which decarboxylative anti-fragmentation of aldol-type adducts is usually considered.

A diaminocyclopentadienone ruthenium complex allows control of regioselectivity in the ruthenium-catalyzed isomerization of propargyl alcohols through the choice of additive. Thereby, both products of the Meyer–Schuster rearrangement and redox isomerization products are selectively accessible. In the presence of hydroxylamine-O-sulfonic acid, unsaturated nitriles are formed instead. The ruthenium catalyst is readily available and stable to moisture, air, and acidic conditions.