Synlett

Photoinduced carbamoylation of ethers using isocyanates as amide sources was accomplished under mild and environmentally friendly reaction conditions. A series of isocyanates were tolerated in this protocol to construct α-amide-substituted ether derivatives with desired yields. The method featured broad substrate scope and good functional group tolerance, which could play an important role in the construction of biological molecules with ethers.

A simple approach for the synthesis of the alkaloid racemosin B has been developed through a photochemical cyclization reaction with a 33% overall yield without any reagents. This method is sustainable and environmentally friendly because no reagents are required to effect the transformation.

We have established an innovative protective approach that disrupts intermolecular interactions to enhance substrate reactivity. Specifically, diacetylimide protection of acetamide prevents the formation of hydrogen bonds, while the incorporation of tert-butyl groups on the aromatic protecting group disrupts π-stacking interactions, both of which culminate in heightened reactivity in glycosylations. We explored the synergistic implementation of these protective measures and applied them to the synthesis of 6-sulfo sialyl Lewis X.

Presented here is a detailed account of the development and implementation of macrocyclic cobaloxime complexes as sulfur-free, catalytic chain transfer agents (CTAs) in crosslinking photopolymerizations. Although much of this review is dedicated to understanding the fundamentals of catalytic chain transfer (CCT) in photopolymerizations, its impact on network topology and resultant mechanical properties, future goals of applying this technology to multimaterial 3D printing are also discussed. It is our long-term ambition for catalytic, sulfur-free CTAs to supplant existing consumptive, sulfur-based agents to provide new, unexplored, and not currently possible to fabricate photopolymeric materials with a specific eye towards application in dentistry, additive manufacturing, and responsive materials.1 Introduction2 History of Catalytic Chain Transfer (CCT)3 Understanding Catalyst Purity and Chain Transfer Activity4 Evidencing CCT in a Crosslinking Photopolymerization5 Comparing Cobalt(II)-Catalysts to Other Relevant CTAs6 Performance of Cobalt(II)-Catalysts in Commercial Resins7 Limitations of Approach and Looking Forward

Acinetobacter baumannii can cause many diseases including septicemia, pneumonia, meningitis, soft tissue, and urinary tract infections. Herein, we described the synthesis of one trisaccharide and two tetrasaccharide fragments derived from A. baumannii ATCC 17961 O-antigen that can be used for screening novel glyco-epitopes and for developing a synthetic carbohydrate-based vaccine against A. baumannii infection. The overall yields for the synthesis of the desired trisaccharide 1, tetrasaccharide 2, and tetrasaccharide 3 are 26.8% (8 steps), 21.6% (9 steps), and 24.5% (6 steps), respectively.

A new nickel-catalyzed electrochemical, reductive cross-coupling for the trideuteromethylation of alkyl and aryl bromides is reported in which CD3 arenesulfonate derivatives were used as effective and readily available CD3 sources. The CD3-labeled products were obtained with good yields. It was demonstrated that this methodology is scalable and can be efficiently used for various methylations, including 13CH3 and 13CD3 labeling.

The transfer hydrogenation of alkenes was realized by using a simple transition-metal compound (FeBr3) and 1,4-cyclohexadiene (1,4-CHD) as the hydrogen donor. The conversion of a number of di- and trisubstituted alkenes was investigated, and even a tetrasubstituted alkene was successfully converted. Compared with previously published work with the more expensive InBr3, the reaction times were considerably reduced and significantly milder reaction conditions could be applied. Interestingly, a transformation that was catalytic in 1,4-CHD, with molecular hydrogen as a stoichiometric reducing agent at 1 bar, was also accomplished.

Hydroxycinnamic acid amides are believed to have antioxidant, antidiabetic, cytotoxic, anticancer, neuroprotective, and antiinflammatory properties, making them interesting target molecules for potential applications in the food, cosmetics, and pharmaceutical industries. Here, we describe the synthesis of hydroxycinnamic acid amides starting from hydroxycinnamic acid esters and the corresponding amines by using variants of the promiscuous hydrolase/acyltransferase from Pyrobaculum calidifontis VA1 (PestE) in water as a solvent. Up to 97% conversion within two hours at 60 °C was achieved with methyl ferulate and tyramine as substrates. This is a promising, environmentally friendly alternative strategy to established chemical synthesis routes or enzymatic methods using lipases in nonaqueous organic solvents.

Due to their strong nucleophilicities, nucleophilic lysine and cysteine residues can be easily recognized and modified by electrophilic groups, thus, acting as the targets for covalent ligands or drugs. Therefore, the development of site-specific protein-modification chemistry for various nucleophilic residues has been explored to label proteins selectively for many biological and therapeutic applications. In this study, we constructed a series of sulfonium-based small molecules to react with the amine group of lysine residues by utilizing the strong electrophilicity of sulfonium, resulting in lysine-selective labeling via the formation of classical amide bonds under alkaline conditions (pH 9.0–11.0). After systematic optimization of the labeling conditions, this strategy was utilized for protein labeling across various bacteria’s lysates. Finally, combined with the activity-based protein profiling (ABPP) strategy, we successfully identified and analyzed hundreds of labeled lysine residues in the bacterial proteome.

The modular synthesis of diverse carbonyl compounds is at the heart of organic synthesis. An optimized protocol for photoredox carbonylation was developed that operates under milder conditions with mesitylacridinium as a photocatalyst. Arenediazonium salts were converted into benzoates (with alcohols), benzoic acids (with water), benzamides (with amines), and chlorides (with 1-butyl-3-methylimidazolium chloride) at 20 bar CO and 20 °C.