Reported herein is a chiral Brønsted acid-catalyzed asymmetric intramolecular allylic amination reaction, allowing facile access to a range of biologically interesting chiral 2-substituted ...hydroquinolines in up to 90% yield and with up to 93% ee. Furthermore, a significant effect of an N-protecting group was observed in this asymmetric process.
Highly efficient: The title reaction provides biologically interesting chiral trifluoromethyl dihydroquinazolinone frameworks in high yields (up to 97 %) and with high enantioselectivities (up to 98 ...% ee), using as low as 1 mol % of catalyst (see scheme). Moreover, anti‐HIV drug candidate DPC 083 was efficiently synthesized using the highly enantioselective aza‐Henry reaction as a key step.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Reported herein is a self-immobilizing near-infrared fluorogenic probe that can be used to image extracellular enzyme activity
. Using a fluorophore as a quinone methide precursor, this probe ...covalently anchors at sites of activation and greatly enhances the fluorescence intensity at 710 nm upon enzymatic stimulus, significantly boosting detection sensitivity in a highly dynamic
system.
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An unprecedented highly enantioselective cascade oxa-Michael−Michael reaction has been developed. The simple and practical process, efficiently catalyzed by chiral diphenylprolinol TMS ether, affords ...a powerful access to highly functionalized synthetically useful chiral chromans. Moreover, notably a new activation mode involving an aminal is disclosed for the first time.
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The development of efficient methods for the facile construction of important molecular architectures is a central goal in organic synthesis. An unprecedented organocatalytic asymmetric cascade ...Michael-alkylation reaction of α,β-unsaturated aldehydes with bromomalonates has been developed. The process, efficiently catalyzed by chiral diphenylprolinol TMS ether in the presence of base 2,6-lutidine, serves as a powerful approach to the preparation of synthetically and biologically important cyclopropanes in high levels of enantio- and diastereoselectivities. Remarkably, the power of the cascade process is fueled by its high efficiency of the production of two new C−C bonds, two new stereogenic centers, and one quaternary carbon center in one single operation, which otherwise is difficult to achieve by traditional strategies. Moreover, the beauty of the cascade process is further underscored by the nature of the product formation depending on the reaction conditions. With the alternation of base from 2,6-lutidine (1.1 equiv), which is effective for the cyclopropanations, to NaOAc (4.0 equiv), the spontaneous ring-opening of cyclopropanes takes place to lead to stereoselective (E) α-substituted malonate α,β-unsaturated aldehydes. A possible reaction mechanism, which involves a Michael-alkylation−retro-Michael pathway, is proposed and verified by experimental studies. This investigation represents the first example of an organocatalyst-promoted ring opening of the cyclopropanes, whereas such reactions have been intensively explored by Lewis acid-based catalysis.
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Going live: A protein‐labeling method based on the use of a single amino acid tag—an N‐terminal cysteine residue—and small‐molecule probes containing a cyanobenzothiazole (CBT) unit has been used for ...the specific fluorescence labeling of proteins in vitro and at the surface of live cells (see scheme). This simple ligation reaction proceeds with a high degree of specificity under physiological conditions. Rd: a rhodamine dye; TEV: tobacco etch virus.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Early diagnosis of tuberculosis can dramatically reduce both its transmission and the associated death rate. The extremely slow growth rate of the causative pathogen, Mycobacterium tuberculosis ...(Mtb), however, makes this challenging at the point of care, particularly in resource-limited settings. Here we report the use of BlaC (an enzyme naturally expressed/secreted by tubercle bacilli) as a marker and the design of BlaC-specific fluorogenic substrates as probes for Mtb detection. These probes showed an enhancement by 100-200 times in fluorescence emission on BlaC activation and a greater than 1,000-fold selectivity for BlaC over TEM-1 β-lactamase, an important factor in reducing false-positive diagnoses. Insight into the BlaC specificity was revealed by successful co-crystallization of the probe/enzyme mutant complex. A refined green fluorescent probe (CDG-OMe) enabled the successful detection of live pathogen in less than ten minutes, even in unprocessed human sputum. This system offers the opportunity for the rapid, accurate detection of very low numbers of Mtb for the clinical diagnosis of tuberculosis in sputum and other specimens.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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.
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An organocatalytic enantioselective addition reaction of cyclic ketoimines with phosphites has been developed for the first time. The process, catalyzed by Soós' quinine thiourea, affords ...synthetically and medicinally interesting enantioenriched trifluoromethyl dihydroquinazolinones in high yields and with high enantioselectivities.
Conjugate addition reactions of a wide range of nucleophilic enol species with enones, catalyzed by a cinchona alkaloid derived thiourea organocatalyst, have been developed with attending good yields ...and high enantioselectivities under a mild reaction condition. The general method provides an efficient approach to the preparation of versatile building blocks possessing various functional groups.
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