Activatable fluorescent probes for real-time imaging-guided tumor therapy.

Surgery and drug therapy are the two principal options for cancer treatment. However, their clinical benefits are hindered by the difficulty of accurate location of the tumors and timely monitoring of the treatment efficacy of drugs, respectively. Rapid development of imaging techniques provides promising tools to address these challenges.

Screening and identification of 3-aryl-quinolin-2-one derivatives as antiviral agents against influenza A.

Quinolin-2-one represents an important and valuable chemical motif that possesses a wide variety of biological activities; however, the anti-influenza activities of quinolin-2-one-containing compounds were rarely reported. Herein, we describe the screening and identification of 3-aryl-quinolin-2-one derivatives as a novel class of antiviral agents. The 3-aryl-quinolinone derivatives were synthesized via an efficient copper-catalyzed reaction cascade that we previously developed.

Modulating Polymerization Thermodynamics of Thiolactones Through Substituent and Heteroatom Incorporation.

A central challenge in the development of next-generation sustainable materials is to design polymers that can easily revert back to their monomeric starting material through chemical recycling to monomer (CRM). An emerging monomer class that displays efficient CRM are thiolactones, which exhibit rapid rates of polymerization and depolymerization. This report details the polymerization thermodynamics for a series of thiolactone monomers through systematic changes to substitution patterns and sulfur heteroatom incorporation.

Alternating Cascade Metathesis Polymerization of Enynes and Cyclic Enol Ethers with Active Ruthenium Fischer Carbenes.

Ruthenium alkoxymethylidene complexes have rarely been demonstrated as active species in metathesis reactions and are frequently regarded as inert. Herein, we highlight the ability of these Fischer-type carbenes to participate in cascade alternating ring-opening metathesis polymerization through their efficient alkyne addition reactions. When enyne monomers are combined with low-strain cyclic vinyl ethers, a controlled chain-growth copolymerization occurs that exhibits high degrees of alternation (>90% alternating diads) and produces degradable poly(vinyl ether) materials with low dispersities and targetable molecular weights.

Efficient Synthesis of Asymmetric Miktoarm Star Polymers.

Asymmetric miktoarm star polymers comprising an unequal number of chemically-distinct blocks connected at a common junction produce unique material properties, yet existing synthetic strategies are beleaguered by complicated reaction schemes that are restricted in both monomer scope and yield. Here, we introduce a new synthetic approach coined "μSTAR" - Miktoarm Synthesis by Termination After Ring-opening metathesis polymerization - that circumvents these traditional synthetic limitations by constructing the block-block junction in a scalable, one-pot process involving (1) grafting-through polymerization of a macromonomer followed by (2) enyne-mediated termination to install a single mikto-arm with exceptional efficiency. This modular μSTAR platform cleanly generates AB and A(BA') miktoarm star polymers with unprecedented versatility in the selection of A and B chemistries as demonstrated using many common polymer building blocks: poly(siloxane), poly(acrylate), poly(methacrylate), poly(ether), poly(ester), and poly(styrene).

Modular Approach to Degradable Acetal Polymers Using Cascade Enyne Metathesis Polymerization.

A modular synthetic approach to degradable metathesis polymers is presented using acetal-containing enyne monomers. The monomers are prepared in a short and divergent synthetic sequence that features two points of modification to tune polymerization behavior and introduce molecular cargo. Steric and stereochemical elements are critical in the monomer design in order to provide rapid and living polymerizations capable of generating block polymers.

Halide-Rebound Polymerization of Twisted Amides.

The first living polymerization of twisted amides is reported, achieved using simple primary alkyl iodides as initiators. Polymerization occurs through a halide-rebound mechanism in which the nucleophilic twisted amide is quaternized and subsequently ring-opened by the iodide counterion. The covalent electrophilic polymerization generates polymers with living chain ends that are both isolable and stable to ambient conditions, enabling the synthesis of block polymers.

Relay Conjugation of Living Metathesis Polymers.

The covalent coupling of complex macromolecules is a modern challenge in both chemistry and biology. The development of efficient and chemoselective methods for polymer coupling and functionalization are increasingly important for designing new advanced materials and interfacing with biochemical systems. Herein, we present a new strategy to directly conjugate living polymers prepared using ring-opening metathesis polymerization (ROMP) to both small molecules and synthetic macromolecules.

Formation of Tertiary Alcohols from the Rhodium-Catalyzed Reactions of Donor/Acceptor Carbenes with Esters.

Rhodium(II)-catalyzed reactions between isopropyl acetate and trichloroethyl aryldiazoacetates result in the formation of oxirane intermediates that ring open under the reaction conditions to form tertiary alcohols. When the reaction is catalyzed by the dirhodium tetrakis(triarylcyclopropanecarboxylate) complex, Rh( S-2-Cl,4-BrTPCP), the tertiary alcohols are formed with good asymmetric induction (80-88% ee).

Scope of the Reactions of Indolyl- and Pyrrolyl-Tethered N-Sulfonyl-1,2,3-triazoles: Rhodium(II)-Catalyzed Synthesis of Indole- and Pyrrole-Fused Polycyclic Compounds.

An efficient synthesis of tetrahydrocarboline-type products and polycyclic spiroindolines has been achieved. The transformation proceeds via rhodium(II)-catalyzed intramolecular annulations of indolyl- and pyrrolyl-tethered N-sulfonyl-1,2,3-triazoles. The reaction could be tuned toward either the formal [3 + 2] cycloaddition or the C-H functionalization reaction depending on the electronic and structural features of the substrates, leading to the production of a variety of structurally related heterocyclic compounds.

Synthesis of 2,2,2,-Trichloroethyl Aryl- and Vinyldiazoacetates by Palladium-Catalyzed Cross-Coupling.

An efficient and convenient synthesis of 2,2,2-trichloroethyl (TCE) aryl- and vinyldiazoacetates was achieved by palladium-catalyzed cross-coupling reactions between TCE diazoacetates and aryl or vinyl iodides. The broad substrate scope allows for rapid and facile formation of TCE aryl- and vinyldiazoacetates, which recently have emerged as versatile reagents for rhodium-carbene chemistry.

Rhodium(II)-Catalyzed C-H Functionalization of Electron-Deficient Methyl Groups.

Enantioselective C-H functionalization of relatively electron-deficient methyl sites was achieved with the combination of 2,2,2-trichloroethyl aryldiazoacetates and tetrakis(triarylcyclopropanecarboxylate) dirhodium catalysts. The substrate scope of the transformation was relatively broad, and C-H functionalization products were furnished with excellent levels of enantioselectivity. As a strategic reaction, crotonate derivatives give 1,6-dicarbonyl compounds, which are useful for further diversification.

One-Step Semisynthesis of a Segetane Diterpenoid from a Jatrophane Precursor via a Diels-Alder Reaction.

A novel segetane diterpenoid (1) and four jatrophane diterpenoids (2-5) were isolated from an acetone extract of Euphorbia peplus. Due to quantity limitations, we prepared 1 via a Diels-Alder reaction, an approach motivated by this compound's biosynthetic pathway and successfully performed X-ray analysis of 1. Furthermore, in an in vitro activity test, 1 exhibited moderate anti-inflammatory activity, whereas both its precursor (2) and the relevant intermediate (2a, IC50 = 1.

Role of ortho-substituents on rhodium-catalyzed asymmetric synthesis of β-lactones by intramolecular C-H insertions of aryldiazoacetates.

A rhodium-catalyzed asymmetric synthesis of β-lactones via intramolecular C-H insertion into the ester group of aryldiazoacetates has been developed. The β-lactones were synthesized in high yields and with high levels of diastereo- and enantioselectivity. Halo and trifluoromethyl substituents at the ortho position of the aryldiazoacetates enhance intramolecular C-H insertions over intermolecular reactions, allowing C-H insertion of even methyl C-H bonds.

Copper-catalyzed tandem reactions of 1-(2-iodoary)-2-yn-1-ones with isocyanides for the synthesis of 4-oxo-indeno[1,2-b]pyrroles.

A novel copper-catalyzed tandem reaction of 1-(2-iodoaryl)-2-yn-1-ones with isocyanides is described. The reaction is through a formal [3 + 2] cycloaddition/coupling tandem process and leads to efficient formation of 4-oxo-indeno[1,2-b]pyrroles.