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The dissemination of antimicrobial resistance around the world is one of the biggest threats to global public health. The acquisition and expression of extended-spectrum β-lactamases (ESBLs) in pathogenic bacterial are mainly responsible for bacterial resistance to third-generation cephalosporins. Reported herein is a ratiometric fluorescent probe for the detection of the activity of ESBLs. This imaging reagent adopts the core structure of cefotaxime as an enzymatic recognition moiety, and exhibits excellent selectivity to ESBLs over other β-lactamases. The specific activation of this sensor by ESBLs can lead to over 2500-fold changes in the fluorescent ratio, which is independent of the concentration of the probe and environmental conditions. Further experiments have demonstrated that this ratiometric fluorescent probe can distinguish bacteria with extended-spectrum antibiotic resistance from a group of clinically important pathogens within a short period of time.

Reported herein is a conceptually novel organocatalytic strategy for the formylation of boronic acids. New reactivity is engineered into the α-amino-acid-forming Petasis reaction occurring between aryl boronic acids, amines, and glyoxylic acids to prepare aldehydes. The operational simplicity of the process and its ability to generate structurally diverse and valued aryl, heteroaryl, and α,β-unsaturated aldehydes containing a wide array of functional groups, demonstrates the practical utility of the new synthetic strategy.

The spread of antibiotic resistance in pathogenic bacteria has become one of the major concerns to public health. Improved monitoring of drug resistance is of high importance for infectious disease control. One of the major mechanisms for bacteria to overcome treatment of antibiotics is the production of β-lactamases, which are enzymes that hydrolyze the β-lactam ring of the antibiotic. In this study, we have developed a self-immobilizing and fluorogenic probe for the detection of β-lactamase activity. This fluorogenic reagent, upon activation by β-lactamases, turns on a fluorescence signal and, more importantly, generates a covalent linkage to the target enzymes or the nearby proteins. The covalent labeling of enzymes was confirmed by SDS-PAGE analysis and MALDI-TOF mass spectrometry. The utility of this structurally simple probe was further confirmed by the fluorescent labeling of a range of β-lactamase-expressing bacteria.

Tuberculosis is a pulmonary disease with an especially high mortality rate in immuno-compromised populations, specifically children and HIV positive individuals. The causative agent, Mycobacterium tuberculosis (Mtb), is a very slow growing and difficult organism to work with, making both diagnosis and development of effective treatments cumbersome. We utilize a fiber-optic fluorescence microendoscope integrated with a whole-body imaging system for in vivo Mtb detection. The system exploits an endogenous enzyme of Mtb (β-lactamase, or BlaC) using a BlaC-specific NIR fluorogenic substrate. In the presence of BlaC, this substrate is cleaved and becomes fluorescent. Using intravital illumination of the lung to excite this probe, sensitivity of the optical system increases over trans- and epi-illumination methods of whole-body fluorescence imaging. We demonstrate that integration of these imaging technologies with BlaC-specific fluorescent reporter probe improves the level of detection to ∼100 colony forming units, a 100× increase in sensitivity in comparison to epi-illumination and a 10× increase in sensitivity in comparison to previous work in intravital excitation of tdTomato-expressing Mtb. This lower detection threshold enables the study of early stage bacterial infections with clinical strains of Mtb and longitudinal studies of disease pathogenesis and therapeutic efficacy with multiple time points in a single animal.

Current methods for the detection of Mycobacterium tuberculosis (Mtb) are either time consuming or require expensive instruments and are thus are not suitable for point-of-care diagnosis. The design, synthesis, and evaluation of fluorogenic probes with high specificity for BlaC, a biomarker expressed by Mtb, are described. The fluorogenic probe CDG-3 is based on cephalosporin with substitutions at the 2 and 7 positions and it demonstrates over 120 000-fold selectivity for BlaC over TEM-1 Bla, the most common β-lactamase. CDG-3 can detect 10 colony-forming units of the attenuated Mycobacterium bovis strain BCG in human sputum in the presence of high levels of contaminating β-lactamases expressed by other clinically prevalent bacterial strains. In a trial with 50 clinical samples, CDG-3 detected tuberculosis with 90 % sensitivity and 73 % specificity relative to Mtb culture within one hour, thus demonstrating its potential as a low-cost point-of-care test for use in resource-limited areas.

A ligand-free Cu-catalyzed [3 + 2] cycloaddition of ethyl 2-(quinolin-2-yl)acetates, ethyl 2-(isoquinolin-1-yl)acetates, and ethyl 2-(pyridin-2-yl)acetates with (E)-chalcones for a “one-pot” synthesis of pyrrolo[1,2-a]quinolines, pyrrolo[2,1-a]isoquinolines and indolizines has been developed. The annulation products were isolated in moderate to good yields with air as the sole oxidant under mild conditions.

A highly enantioselective addition of alcohols to cyclic trifluoromethyl ketimines is developed catalyzed by quinine-thiourea, giving biologically interesting N,O-ketals in up to 99% yield and 96% ee.

The procedure allows the access to biologically important chiral dihydroquinazolinones bearing a -CF3 function at the quaternary carbon.

An entirely metal-free catalyst system consisting of an easily prepared recyclable new TEMPO derived sulfonic salt catalyst, and mineral acids (NaNO2 and HCl) has been developed for selective aerobic oxidation of structurally diverse benzylic sp3 C–H bonds of ethers and alkylarenes. The mild reaction conditions allow for the generation of synthetically and biologically valued isochromanones and xanthones from readily accessible alkyl aromatic precursors in good yields.

The reaction of 1-naphthol (I) and substituted analogues (VI) with various unsaturated aldehydes under conditions A) in the presence of piperidine affords exclusively C-4 substituted, highly functionalized derivatives as (E) isomers (E:Z < 95:5).

This communication describes a novel protein labeling method that uses a single amino-acid tag — N-terminal cysteine residue — and small-molecule probes carrying the cyanobenzothiazole unit for specific labeling of proteins in vitro and at the surface of live cells. This simple ligation reaction proceeds with a high degree of specificity in physiological conditions, and should offer an important alternative to currently available protein labeling methods.

A direct preparation of synthetically useful α,β-unsaturated aldehydes from readily available aldehydes has been developed. The process is effectively cocatalyzed by an amine-palladium acetate to give rise to α,β-unsaturated aldehydes in moderate to good yields (41―62%). The reaction features the use of unmodified aldehydes rather than enol silyl ethers, which are used in a typical Saegusa oxidation reaction.

An efficient, organocatalytic, highly enantioselective, conjugate addition reaction of nitromethane with α,β-unsaturated aldehydes has been developed. The process serves as the key step for a practical 3-step synthesis of chiral baclofen, an anti-spastic drug.

A quinine-promoted, enantioselective Michael addition reaction of diphenyl phosphite with nitroalkenes has been developed. This methodology affords a facile access to enantiomerically enriched p-nitrophosphates, precursors for the preparation of synthetically and biologically useful β-amino-phosphonates.

A Pd(OAc)2-catalyzed divergent synthesis of multisubstituted imidazoles and quinazolines from N-allylamidines has been developed. In the presence of oxidant O2 from air and/or a ligand and Pd(OAc)2, imidazoles were obtained. Nonetheless, under microwave (MW) irradiation in a sealed system, quinazolines as major products were produced.

A chiral amine catalyzed enantioselective α-functionalization of α-substituted β-ketocarbonyls with electron-deficient vinylarenes has been developed to construct the dicarbonyl products with the formation of a chiral all-carbon quaternary stereocenter. The products can be used for the efficient synthesis of useful but challenging chiral quaternary centered pyrazolones.

High yields and enantioselectivities are obtained for substrates bearing a -CF3 function at C-4.

Enantioenriched α-aminophosphate analogues (III) of the non-nucleoside reverse transcriptase inhibitor DPC-083 are readily obtained by an asymmetric hydrophosphonylation of quinazolinones (I).

A direct preparation of synthetically useful α,β-unsaturated aldehydes from readily available aldehydes has been developed. The process is effectively cocatalyzed by an amine-palladium acetate to give rise to α,β-unsaturated aldehydes in moderate to good yields (41―62%). The reaction features the use of unmodified aldehydes rather than enol silyl ethers, which are used in a typical Saegusa oxidation reaction.

An unprecedented highly enantioselective cascade oxa-Michael−Michael reaction has been developed. The simple and practical process, efficiently catalyzed by chiral diphenylprolinol TMS ether, affor...

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.

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.

The first enantioselective conjugate addition reaction of 1 H-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.

[reaction: see text] A novel organocatalytic, enantioselective domino double Michael addition reaction of alpha,beta-unsaturated aldehydes with ethyl 4-mercapto-2-butenoate has been developed. The process is promoted by chiral diphenylprolinol TMS ether to give chiral tetrahydrothiophenes in high to excellent levels of enantioselectivities.

Highly enantio- and diastereoselective tandem Michael−aldol reactions, efficiently catalyzed by a cinchona alkaloid thiourea via synergistic noncovalent hydrogen-bonding activation of both the Michael donor and acceptor, have been developed. The process affords a powerful means for the construction of versatile chiral thiochromanes with the formation of three stereogenic centers in a one-pot synthesis from simple achiral compounds.