Vistas in the field of 1,3-oxathiolan-5-ones: Synthesis and chemical reactivity

This review covers many reports of the applications of multicomponent domino reactions (MDRs) in the synthesis of novel stereocontrolled mercapto-heterocycles from the 1972 up to the end of 2016. The reported approaches were employed for modifications of the oxathiolanone core for new construction of a mercapto-heterocycles scaffold from mercaptoacetyl transfer agent with various reagents.     

Synthesis of Some New Fused and Binary 1,3,4‐Thiadiazoles as Potential Antitumor and Antioxidant Agents

Annulations of 2‐amino‐1,3,4‐thiadiazole ( 1 ) with α,β‐unsaturated carbonyl compounds 2 , 5 , and 9 afforded thiadiazolo[3,2‐a]pyrimidin 3 , benzamide 7 , and bis‐pyrazole derivative 11 . Cyclization of benzamide 7 with POCl₃ gave binary imidazole derivative 8 . Moreover, alkylation of 1 with 2‐bromo‐1‐(2H‐chromen‐3‐yl) ethanone ( 9 ) followed by cyclization gave imidazo[2,1‐b]‐1,3,4‐thiadiazole derivative 15 . Multicomponent reaction of 1 with heterocyclic and/or aromatic aldehyde and thioglycolic acid afforded the corresponding thiazolidinones 17 and 19 . Finally, a one‐pot synthesis of 1 with isatin and thiosemicarbazide furnished the spirotriazole 20 . The newly synthesized compounds were evaluated as antitumor agents.     

Role of Phenylpropanoids and Flavonoids in Plant Resistance to Pests and Diseases

Phenylpropanoids and flavonoids are specialized metabolites frequently reported as involved in plant defense to biotic or abiotic stresses. Their biosynthetic accumulation may be constitutive and/or induced in response to external stimuli. They may participate in plant signaling driving plant defense responses, act as a physical or chemical barrier to prevent invasion, or as a direct toxic weapon against microbial or insect targets. Their protective action is described as the combinatory effect of their localization during the host’s interaction with aggressors, their sustained availability, and the predominance of specific compounds or synergy with others. Their biosynthesis and regulation are partly deciphered; however, a lot of gaps in knowledge remain to be filled. Their mode of action on microorganisms and insects probably arises from an interference with important cellular machineries and structures, yet this is not fully understood for all type of pests and pathogens. We present here an overview of advances in the state of the art for both phenylpropanoids and flavonoids with the objective of paving the way for plant breeders looking for natural sources of resistance to improve plant varieties. Examples are provided for all types of microorganisms and insects that are targeted in crop protection. For this purpose, fields of phytopathology, phytochemistry, and human health were explored.     

Synthesis and Characterization via Molecular Quantum Parameters of 2H‐Thiazolo[3,2‐a]pyrimidine‐3,5,7(6H)‐trione

2H‐Thiazolo[3,2‐a]pyrimidine‐3,5,7(6H)‐trione ( 2 ) was synthesized and characterized via molecular quantum parameters using the PM3‐semiempirical MO method. This is considered the only route not previously reported in the literature to synthesize compound 2 from 2‐imino‐4‐thiazolidinone ( 1 ).     

The Performance of an Electrorheological Fluid in Dynamic Squeeze Flow: The Influence of Solid Phase Size

This paper is concerned with an experimental investigation of a comparison of the rheological performance of an ER fluid, consisting of a carrier with a range of solid phase sizes, in oscillatory squeeze-flow under DC conditions. The fluid is sandwiched between two parallel plane electrodes, the upper one stationary and the lower one oscillating normal to its plane. It is seen that the dynamic performance of the fluid, in terms of the capacity for the transmission of imposed forces across the fluid, is highly dependent on the size of the dispersed solid phase and has an optimum value which is dependent on the mean value of the interelectrode gap. In addition the paper includes some measurements of the current through the fluid which may help to shed some further light on the mechanism of the ER effect. Finally the implications of the results to vibration control are discussed. Copyright 1999 Academic Press.     

Chemoselective Synthesis of Enamino‐Coumarin Derivatives Identified as Potent Antitumor Agents

The reaction of 4‐aminocoumarin ( 2 ) with benzaldehyde gave the bisenamino derivatives 4 . Thus, transamination of 2 with o‐phenylenediamine furnished enamino skeleton 3 , which can be obtained from 1 . Reaction of 1 with 5‐aminoisoxazole afforded 5 . While reaction of 2 with benzalaniline, isatinanil and phenyl isothio cyanate afforded the corresponding 7 , 8 and 9 , respectively. Heterocyclic annulations of 2‐phenylthiazolidine‐4‐one 10 2‐phenylthiazolidin‐4‐one 10 and 2‐phenyl‐thiazinan‐4‐one 11 systems were achieved via reaction of 2 with benzaldehyde and rather either 2‐mercaptoacetic acid or 3‐mercaptopropanoic acid respectively. The behavior of 2 towards monochloro acetic acid and 4‐oxo‐4‐phenylbuatonic 4‐Oxo‐4‐phenylbutanoic acid was investigated. All of the newly synthesized compounds were evaluated as antitumor (cytotoxic) agents. Most of these compounds have shown significant antitumor activities.     

Highlights on the synthesis of novel phenothiazine-based azines scaffold as antioxidant agents

Azines derivatives of phenothiazines were synthetically constructed from one-pot multicomponent reactions of 1-(4a,10a-dihydro-10H-phenothiazin-2-yl)ethan-1-one with various reagents. The obtained novel target compounds were evaluated as antioxidant agents using ABTS^+• scavenging assay. Antioxidant results revealed that the incorporation of azines to phenothiazine ring system enhanced the activity. In addition, compound 18 prevent the damage of DNA due to the formation of bleomycin-iron complex more than the standard compound.     

Synthesis,PM3‐Semiempirical,and Biological Evaluation of Pyrazolo[4,3‐c]quinolinones

A series of α,β‐unsaturated ketones containing quinolone moieties 2 , 3 , 4 , 5 , 6 were synthesized by condensation of 7‐methoxyquinoline‐2,4(1H,3H)‐dione ( 1 ) with different aryl aldehydes. Pyrazole derivatives 8 , 9 , 10 , 11 were also synthesized via refluxing of α,β‐unsaturated ketones 2 , 3 , 4 , 5 , 6 with hydrazine derivatives. Newly synthesized compounds were characterized by elemental analyses, spectral data, and screened for their antioxidant and antitumor activities. Geometrical optimizations of the molecular structures for different synthesized compounds were studied.     

Synthesis and In Vitro Antitumor Activity of New Isoxazolo[5,4‐d]Pyrimidine Systems

The reaction of 5‐amino‐3‐methylisoxazole ( 1 ) with aldimines 2 , 3 , 4 , 5 , 6 , 7 gave basic side chain 5‐amino‐3‐methylisoxazole derivatives 8 , 9 , 10 , 11 , 12 , 13 . Annulations of derivatives 8 , 9 , 10 , 11 , 12 , 13 with anisaldehyde afforded the target isoxazolo[5,4‐d]pyrimidines 14 , 15 , 16 , 17 . Treatment of 1 with isatin ketimine anil 18 resulted in the formation of derivative 19 , which further cyclized with anisaldehyde afforded the spirotetracyclic system 20 . Mannich reaction of 1 with primary amine such as methylamine and benzylamine gave the corresponding isoxazolo[5,4‐d]pyrimidine derivatives 21 and 22 , respectively. The newly synthesized compounds were tested for their antitumor activity.