Hybridization of the Pharmacophoric Features of Discoipyrrole C and Combretastatin A-4 toward New Anticancer Leads

Pharmacophore hybridization is an attractive strategy to identify new leads against multifactorial diseases such as cancer. Based on literature analysis of compounds possessing 'vicinal diaryl' fragment in their structure, we considered Discoipyrroles A-D and Combretastatin A-4 (CA-4) as possible components in hybrid design. Discoipyrrole C (Dis C) and CA-4 were used as reference compounds in these studies and their hybrids, in the form of 4,5-diaryl-1H-pyrrol-3(2H)-ones, were synthesized from suitable amino acid precursors though their ynone intermediates. Of these, the hybrid having exact substitution pattern as that of CA-4 showed better potency and selectivity than Dis C, but its activity was less compared to CA-4. This new analog disrupted interphase microtubules by inhibiting tubulin assembly by binding to the colchicine site, induced multipolar spindles, caused cell cycle block and apoptosis in HeLa cells. It also inhibited colony formation and migration of breast cancer cell lines.

A dual mode 'turn-on' fluorescence-Raman (SERS) response probe based on a 1H-pyrrol-3(2H)-one scaffold for monitoring H2S levels in biological samples

Discovery of the biological signaling roles of H2S has spurred great interest in developing reliable methods for its accurate detection and quantification. As considerable variation in its levels is seen during pathological conditions such as sepsis, real-time quantification methods have relevance in diagnosis as well. Of various approaches, reaction-based probes which respond through 'off-on' fluorescence emission remain the most studied. Since the intensity of emission is related to the analyte concentration in these measurements, the presence of built-in features which provide an opportunity for internal referencing will be advantageous. In view of this, a dual mode response system that senses H2S through characteristic fluorescence and Raman (SERS) signals based on a 1H-pyrrol-3(2H)-one scaffold was developed and is the main highlight of this report. This probe offers several advantages such as fast response (<1 min), and high selectivity and sensitivity with a detection limit of ∼7 nM. Imaging of H2S in HepG2 cells, making use of the SERS signal from the thiolysis product is also demonstrated.

A micro-flow rapid dual activation approach for urethane-protected α-amino acid N-carboxyanhydride synthesis

This study demonstrated the rapid dual activation (10 s, 20 °C) of a combination of an α-amino acid N-carboxyanhydride and alkyl chloroformate in the synthesis of a urethane-protected α-amino acid N-carboxyanhydride in a micro-flow reactor. The key to success was the combined use of two amines that activated both substrates with proper timing. Three amines, i-Pr₂NEt, Me₂NBn, or N-ethylmorpholine, were used with pyridine in accordance with the steric bulkiness of a side chain in the α-amino acid N-carboxyanhydride. A variety of 16 urethane-protected α-amino acid N-carboxyanhydrides were synthesized in high yields. The role of amines was investigated based on the measurement of the time-dependent (0.5 to 10 s) decrease of α-amino acid N-carboxyanhydrides and alkyl chloroformates in the presence of amines via flash mixing technology using a micro-flow reactor. It was suggested that the in situ generated acylpyridinium cation was highly active and less prone to causing undesired decomposition compared with the acylammonium cation examined in this study. Thus, even at a very low concentration, the acylpyridinium cation facilitated the desired coupling reaction.

Sc(OTf)3-Catalyzed Iodocyclization/Ritter-Type Amidation of N-Alkoxypropiolamides: A Synthetic Strategy for Isoxazol-3(2H)-ones

A Sc(OTf)₃-catalyzed iodocyclization/Ritter-type amidation of N-alkoxypropiolamides for the synthesis of 4-iodoisoxazol-3(2H)-ones bearing an amide group has been developed. This domino protocol allows the construction of a valuable heterocycle, isoxazol-3(2H)-one, as well as the introduction of two functional groups. The reaction has a broad substrate scope and can be carried out on a large scale. Control experiments suggest that Sc(OTf)₃ acts as a dual activator for both the iodocyclization and amidation steps. In addition, the N-alkoxy group in the substrate suppresses some of the side reactions.

Synthesis of 1 H-Pyrrol-3(2 H)-ones via Three-Component Reactions of 2,3-Diketo Esters, Amines, and Ketones

An efficient one-pot, three-component reaction of 2,3-diketo esters with amines and ketones has been developed for the synthesis of 1 H-pyrrol-3(2 H)-ones. By using trifluoroacetic acid (TFA) as the additive and acetonitrile (MeCN) as the solvent, this convenient method provides a library of 1 H-pyrrol-3(2 H)-ones in moderate to good yields. The simple protocol features readily available starting materials, a straightforward process, good functional group tolerance, and broad substrate scope.

Switching the regioselectivity in the copper-catalyzed synthesis of iodoimidazo[1,2-a]pyridines

A unique copper-catalyzed binucleophilic switching of 2-aminopyridine has been developed for the regioselective synthesis of 2- and 3-iodoimidazo[1,2-a]pyridines using alkenes/alkynes as coupling partners in the presence of molecular iodine under aerobic reaction conditions. This method was also applied to the synthesis of 2-iodo-3-phenylbenzo[d]imidazo[2,1-b]thiazoles. This protocol offers an easy route towards the synthesis of 2,3-diarylimidazo[1,2-a]pyridines.

Halogenoheterocyclization of 2-(allylthio)quinolin-3-carbaldehyde and 2-(propargylthio)quinolin-3-carbaldehyde

The reaction of 2-allyl(propargyl)thioquinolin-3-carbaldehyde with halogens (Br or I) results in formation of 1-halogenomethyl(halogenomethylidene)-4-formyl-1,2-dihydrothiazolo[3,2-

Synthesis of [1,3]thiazolo[3,2-b][1,2,4]triazol-7-ium and [1,2,4]triazolo[5,1-b][1,3]thiazin-4-ium salts via regioselective electrophilic cyclization of 3-[(2-alken-1-yl)sulfanyl]-4H-1,2,4-triazoles

A convenient procedure for the regioselective preparation of [1,3]thiazolo[3,2-b][1,2,4]triazol-7-ium 10 and [1,2,4]triazolo[5,1-b][1,3]thiazin-4-ium salts 9 via regioselective electrophilic cyclization of 3-[(2-alken-1-yl)sulfanyl]-4H-1,2,4-triazoles 3 is reported. Direction of electrophilic heterocyclization strongly depends on nature of the alkenyl substitutent.