Search

Research has been conducted on the allene chemistry. The results of the palladium(0)-catalyzed coupling-cyclization of 2,3-allenamides and organic iodides are presented.

A methodology was presented which offers an efficient general high-yielding route to beta, gamma-unsaturated beta-haloketones with different substitution patterns. It makes use of a finding that 3,4-pentadien-2-one's hydrohalogenation reaction with metal halides in HOAc at room temperature selectively afforded 4-halo-4-penten-2-ones in high yields. It possesses utility in the organic synthesis of coumpounds such as homoallylic alcohols and substituted beta, gamma-unsaturated enones.

Superresolution imaging methods based on sequential imaging of sparse sublets of single molecules require fluorophores whose emission is photoactivated or photoswitched. The design and application of HaloTag-based target-specific azido DCDHFs, a class of photoactivatable push-pull fluorogens that produce bright fluorescent labels suitable for single-molecule superresolution imaging in live bacterial and fixed mammalian cells, is described.

A new amine-catalyzed cascade Michael-alkylation process is described for generating highly functionaluzed chiral cyclopropanes in one-pot transformation. The analysis has shown that both the organocatalyst diphenylprolinol TMS ether and the base NaOA has played essential roles in the formation of the products.

A diarylprolinol silyl ether organocatalyzed tandem Michael-aldol reaction of [alpha],[beta]-unsaturated aldehydes with 2-mercaptobenzaldehydes is discovered which affords chiral thiochromenes. This new methodology serves as a facile approach for the preparation of a range of substituted thiochromanes containing three chiral centres in high enantiomeric excesses and excellent diastereoselectivities.

An efficient and general conjugate addition of a broad spectrum of nucleophilic enol species to enones, catalyzed by a cinchona alkaloid derived thiourea organocatalyst, is reported. The reaction affords excellent enantioselectivity and high yields for a diverse array of nucleophiles, including malonate esters, ketoesters, 1,3-diketones, nitroesters, and 1,3-dinitriles and enones as electrophiles.

Slow growth of Mycobacterium tuberculosis, the causative agent of tuberculosis, hinders advancement in all areas of research toward prevention and treatment. Real-time imaging with reporter enzyme fluorescence (REF) that uses custom fluorogenic substrates for bacterial enzymes allows rapid and specific detection of M. tuberculosis in live animals. We have synthesized a novel REF substrate, CNIR800, that carries a near-infrared (NIR) fluorochrome IRDye 800CW, with a quencher connected through the lactam ring that is hydrolyzed by the enzyme BlaC (ß-lactamase) that is naturally expressed by M. tuberculosis. CNIR800 produces long-wavelength emission at 795 nm upon excitation (745 nm) and exhibits significantly improved signal to noise ratios for detection of M. tuberculosis. The detection threshold with CNIR800 is approximately 100 colony-forming units (CFU) in vitro and <1000 CFU in the lungs of mice. Additionally, fluorescence signal from cleaved CNIR800 reaches maximal levels 4-6 hours after administration in live animals, allowing accurate evaluation of antituberculous drug efficacy. Thus, CNIR800 represents an excellent substrate for accurate detection of M. tuberculosis rapidly and specifically in animals, facilitating research toward understanding pathogenic mechanisms, evaluation of therapeutic outcomes, and screening new vaccines. [ABSTRACT FROM AUTHOR]

An organocatalytic direct inverse electron demand Diels–Alder reaction of ketones with 1,2,4,5-tetrazines has been developed. The process is efficiently catalyzed by proline to give Diels–Alder adducts pyridazines in high yields. [ABSTRACT FROM AUTHOR]

Fluorous (S) pyrrolidine sulfonamide serves as an efficient promoter for highly enantioselective aldol reactions of ketones and aldehydes with aromatic aldehydes on water. A notable feature of the organocatalyst is that it can be recovered from the reaction mixtures by simple fluorous solid-phase extraction and subsequently reused (up to seven cycles) without a significant loss of catalytic activity and stereoselectivity. [ABSTRACT FROM AUTHOR]

The first enantioselective conjugate addition reaction of 1H-benzotriazole with a variety of enones has been developed. The process, catalyzed by a cinchona alkaloid thiourea, affords Michael adducts in good yields and with moderate to good enantioselectivities. [ABSTRACT FROM AUTHOR]

Under the catalysis of 1 mol % Pd(PPh[sub 3])[sub 4], the reaction of 4,4-disubstituted 2,3-allenamides and organic iodides in toluene afforded iminolactones stereospecifically in >90% yields using K[sub 2]CO[sub 3] (2 equiv) 5 mol % TBAB as the base. A similar reaction with 4-monosubstituted 2,3-allenamides afforded γ-hydroxy-γ-lactams in relatively lower yields. The N/O-attack selectivity may be determined by the steric effect at the 4-position of 2,3-allenamides. [ABSTRACT FROM AUTHOR]

This communication reports the use of click chemistry to site-specifically conjugate bioluminescent Renillaluciferase proteins to gold nanoparticles (Au NPs) for sensing protease activity. The bioluminescent emission from luciferase was efficiently quenched by Au NPs, but significantly recovered after the proteolytic cleavage. [ABSTRACT FROM AUTHOR]

An unprecedented highly enantio- and diastereoselective cascade aza-Michael–Michael reaction of α,β-unsaturated aldehydes with trans-γ-Ts protected amino α,β-unsaturated ester has been developed; the simple and practical process, efficiently catalyzed by chiral diphenylprolinol TMS ether, serves as a powerful access to highly functionalized trisubstituted chiral pyrrolidines. [ABSTRACT FROM AUTHOR]

The article presents information on the development of a cinchona thiorea VI-promoted asymmetric conjugate addition of various nucleophilic enol species to enones. The power of conjugate addition reactions, in the study, is fueled by a wide variety of substances that can serve as electrophiles and nucleophiles.