Total Synthesis of Lamellarins U and A3 by Interrupting Halogen Dance

A total synthesis of lamellarins U and A3 is described. The synthesis features interruption of a halogen dance reaction of a metalated α,β-dibromopyrrole. The pyrrolylmagnesium reagent, generated by deprotonative metalation using (TMP)MgCl·LiCl (TMP: 2,2,6,6-tetramethylpiperidide) as base, was transmetalated to the corresponding organozinc species without causing the halogen dance reaction, which underwent a Negishi coupling to incorporate an aryl group onto the pyrrole ring. The arylated α,β-dibromopyrrole was then converted into lamellarins U and A3 through an α-selective halogen–magnesium exchange followed by carboxylation and subsequent palladium-mediated cyclization. The late-stage introduction of another aryl group was performed using a Kosugi–Migita–Stille coupling to provide lamellarins U and A3.

Investigation of Leoligin Derivatives as NF-κΒ Inhibitory Agents

The transcription factor NF-κB is an essential mediator of inflammation; thus, the identification of compounds that interfere with the NF-κB signaling pathway is an important topic. The natural products leoligin and 5-methoxyleoligin have served as a starting point for the development of NF-κB inhibitors. Using our modular total synthesis method of leoligin, modifications at two positions were undertaken and the effects of these modifications on the biological activity were investigated. The first modification concerned the ester functionality, where it was found that variations in this position have a significant influence, with bulky esters lacking Michael-acceptor properties being favored. Additionally, the substituents on the aryl group in position 2 of the tetrahydrofuran scaffold can vary to some extent, where it was found that a 3,4-dimethoxy and a 4-fluoro substitution pattern show comparable inhibitory efficiency.

Tethered Aryl Groups Increase the Activity of Anti-Proliferative Thieno[2,3-b]Pyridines by Targeting a Lipophilic Region in the Active Site of PI-PLC

The compounds 2-amino-3-carboxamido-thieno[2,3-b]pyridines have demonstrated excellent anti-proliferative activity against human cancer cell lines, including the triple-negative breast cancer cell line MDA-MB-231. In this study, 81 novel thieno[2,3-b]pyridines were synthesised in four series to further improve their anti-proliferative activity, in particular by targeting an adjacent lipophilic pocket in the putative target enzyme phosphoinositide phospholipase C (PI-PLC). Overall, it was found that appending a propyl-aryl group at C-5 on 2-amino-3-carboxamido-thieno[2,3-b]pyridine resulted in compounds with potent biological activity, exhibiting IC50 values in the nanomolar range. The propyl linker could be an α,β-unsaturated ketone or a saturated propyl ketone, but the highest activity was obtained when allylic alcohols were the tether between thieno[2,3-b]pyridine and the appended aryl group, with compound 21r having IC50 values lower than 50 nM. Compounds with one extra carbon in the tether (i.e., a four-atom chain) were found to be considerably less active. Molecular modelling revealed this propyl tether places the newly introduced aryl ring in an untargeted lipophilic pocket within the active site of the phosphoinositide phospholipase C (PI-PLC) enzyme.

Low-Dimensional Architectures in Isomeric cis-PtCl2{Ph2PCH2N(Ar)CH2PPh2} Complexes Using Regioselective-N(Aryl)-Group Manipulation

The solid-state behaviour of two series of isomeric, phenol-substituted, aminomethylphosphines, as the free ligands and bound to PtII, have been extensively studied using single crystal X-ray crystallography. In the first library, isomeric diphosphines of the type Ph2PCH2N(Ar)CH2PPh2 [1a–e; Ar = C6H3(Me)(OH)] and, in the second library, amide-functionalised, isomeric ligands Ph2PCH2N{CH2C(O)NH(Ar)}CH2PPh2 [2a–e; Ar = C6H3(Me)(OH)], were synthesised by reaction of Ph2PCH2OH and the appropriate amine in CH3OH, and isolated as colourless solids or oils in good yield. The non-methyl, substituted diphosphines Ph2PCH2N{CH2C(O)NH(Ar)}CH2PPh2 [2f, Ar = 3-C6H4(OH); 2g, Ar = 4-C6H4(OH)] and Ph2PCH2N(Ar)CH2PPh2 [3, Ar = 3-C6H4(OH)] were also prepared for comparative purposes. Reactions of 1a–e, 2a–g, or 3 with PtCl2(η4-cod) afforded the corresponding square-planar complexes 4a–e, 5a–g, and 6 in good to high isolated yields. All new compounds were characterised using a range of spectroscopic (1H, 31P{1H}, FT–IR) and analytical techniques. Single crystal X-ray structures have been determined for 1a, 1b∙CH3OH, 2f∙CH3OH, 2g, 3, 4b∙(CH3)2SO, 4c∙CHCl3, 4d∙½Et2O, 4e∙½CHCl3∙½CH3OH, 5a∙½Et2O, 5b, 5c∙¼H2O, 5d∙Et2O, and 6∙(CH3)2SO. The free phenolic group in 1b∙CH3OH, 2f∙CH3OH,2g, 4b∙(CH3)2SO, 5a∙½Et2O, 5c∙¼H2O, and 6∙(CH3)2SO exhibits various intra- or intermolecular O–H∙∙∙X (X = O, N, P, Cl) hydrogen contacts leading to different packing arrangements.

Enantioselective Synthesis, Tautomerism, Molecular Docking And Biological Evaluation of 4-Hydroxy-3-(3-Oxo-1-Phenylbutyl)-2H-Chromen-2-One Analogues

Keeping in view the aim of better alternatives of 4-Hydroxy-3-(3-oxo-1-phenylbutyl)-2H-chromen-2-one (warfarin), eleven analogs of warfarin have been synthesized with the goal to increase enantioselectivity of (S) enantiomer by using appropriate catalyst and minimize tautomerism by replacing methyl group of the side chain with aryl group. There are many reports of the serious complications with warfarin use, which are associated with the tautomeric forms of warfarin. The key step was highly enantioselective Michael addition of variously substituted chalcone and 4-hydroxycoumarin by using cinchona based 9-amino-9-deoxyepiquinine as chiral catalyst. Synthesized compounds were characterized by IR, 1HNMR,13CNMR, EIMS and CD studies. Enantiomeric excess (%ee) was determined by chiral HPLC which was upto 98%. Synthesized analogues were screened for anticoagulant, antibacterial and antifungal activities. In-vitro anticoagulant activity was evaluated by plasma recalcification time (PRT) method and out of eleven, ten synthesized compounds showed improved IC50 values as compaired to IC50 values of standard drug warfarin. Compound 4 showed 68.25% inhibation against staphylococcus aureus and compound 7 showed 68% inhibation against bacillus subtillis, gram positive strains of bacteria, compound 6 shows 70% inhibation against fungal strain candida albicans. Furthermore, molecular docking studies were carried out with Vitamin K1 epoxide reductase VKOR1 receptor 3kp9, a potential target of warfarin for anticoagulant activity.

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

In the presence of a suitable acid or base, α-hydroxyaldehydes, ketones, and imines can undergo isomerization that features the 1,2-shift of an alkyl or aryl group. In the process, the hydroxy group is converted to a carbonyl and the aldehyde/ketone or imine is converted to an alcohol or amine. Such α-ketol/α-iminol rearrangements are used in a wide variety of synthetic applications including asymmetric synthesis, tandem reactions, and the total synthesis and biosynthesis of natural products. This review explores the use of α-ketol rearrangements in these contexts over the past two decades.

Carbene Character in a Series of Neutral PCcarbeneP Cobalt(I) Complexes – Radical Carbenes Versus Nucleophilic Carbenes

Cobalt(I) complexes supported by a series of PCcarbeneP pincer ligands of varying donicity, differing in the aryl group linking the phosphine arms with the anchoring carbon donor, are described. Addition of the proligands to cobalt bromide results in the formation of a series of cobalt(II) tetrahedral complexes, Ln-1, which serve as excellent precur-sors to the corresponding PCalkylP and PCcarbeneP complexes. Square planar cobalt PCcarbeneP complexes, L2R-3-X (X = Cl, Br), are readily synthesized by addition of a bulky aryloxide radical to the corresponding PCalkylP complex, L1-2-Br or via addition of L2R to ClCo(PPh3)3 in the presence of trityl radical or by addition of NaHBEt3 and trityl radical to iso-lated L2R-1. For the L2NMe2 PCcarbeneP complexes, salt metathesis reactions with either CsOH·H2O, LiCH2TMS, or LiNH2 result in the corresponding hydroxo, alkyl, and amine complexes, L2NMe2-3-R (R = OH, CH2TMS, NH2). Reaction of L2NMe2-3-OH with benzoic acid affords the 2-O2CPh derivative The nature of the carbene bond in either ligand plat-form as well as the effects of the X-type capping ligand on the Co=C bond are explored computationally and show that triplet structures are relatively more stable in for the less electron donating ligand L1 while singlet Co(I) carbenes dominate for the more electron rich L2 derivatives. For L2NMe2 complexes, the effect of the trans ligand X was also probed. Pi donors imbue the carbene with singlet character while the strongly  donating alkyl derivative exhibits significant triplet character.

An engineered, orthogonal auxin analog/AtTIR1(F79G) pairing improves both specificity and efficacy of the auxin degradation system in Caenorhabditis elegans

The auxin-inducible degradation system in C. elegans allows for spatial and temporal control of protein degradation via heterologous expression of a single Arabidopsis thaliana F-box protein, transport inhibitor response 1 (AtTIR1). In this system, exogenous auxin (Indole-3-acetic acid; IAA) enhances the ability of AtTIR1 to function as a substrate recognition component that adapts engineered degron-tagged proteins to the endogenous C. elegans E3 ubiquitin ligases complex (SKR-1/2-CUL-1-F-box (SCF)), targeting them for degradation by the proteosome. While this system has been employed to dissect the developmental functions of many C. elegans proteins, we have found that several auxin-inducible degron (AID)-tagged proteins are constitutively degraded by AtTIR1 in the absence of auxin, leading to undesired loss-of-function phenotypes. In this manuscript, we adapt an orthogonal auxin-derivative/mutant AtTIR1 pair (C. elegans AID version 2 (C.e.AIDv2)) that transforms the specificity of allosteric regulation of TIR1 from IAA to one that is dependent on an auxin derivative harboring a bulky aryl group (5-Ph-IAA). We find that a mutant AtTIR1(F79G) allele that alters the ligand binding interface of TIR1 dramatically reduces ligand-independent degradation of multiple AID*-tagged proteins. In addition to solving the ectopic degradation problem for some AID targets, addition of 5-Ph-IAA to culture media of animals expressing AtTIR1(F79G) leads to more penetrant loss-of-function phenotypes for AID*-tagged proteins than those elicited by the AtTIR1-IAA pairing at similar auxin analog concentrations. The improved specificity and efficacy afforded by the mutant AtTIR1(F79G) allele expands the utility of the AID system and broadens the number of proteins that can be effectively targeted with it.

An Insight into 4-Thiazolidinones

Aims: This assessment is all about to get imminent into 4-thiazolidinones and comprehensively reviewing this molecule. 4-Thiazolidinones are known for their wide-ranging biological activities. 4 - Thiazolidinones contains thiazolidine ring having carbonyl group in the 4-position. The chemistry of thiazolidinones has drawn scientific interest through the years because this particular ring system is the core structure in a variety of synthetic compounds with a broad spectrum of biological activities such as anti-bacterial, anti-fungal, insecticidal, anti-epileptic, anti-mycobacterial, anti- inflammatory, anti-parasitic, hypnotic and anti-cancer. Structural modifications on the 4-thiazolidinone moiety, either by replacing the aryl group with the heteroaryl scaffold or by incorporating different groups and moieties (A&B) on –CH– group of nucleus paving a new pathway for the future research. It necessitates to widely reviewing the structure, chemistry and pharmacological aspects of 4-thiazolidinones.