The Synthesis of Novel Gallium Carbenes, Nitrenes, Phosphinidenes and Alkoxides

<p>In the present study, synthetic routes to formal double bonds between gallium and carbon (fig 1), nitrogen (fig 2), and phosphorus (fig 3) have been investigated. These synthetic routes utilised the monoanionic, four electron donor, β-diketiminate (BDI) ligand to provide both steric and electronic stabilisation to three coordinate gallium complexes. The known di-substituted β-diketiminatogallium complexes: [(BDI)GaMe₂] and [(BDI)Ga(NHPh)₂], as well the new complexes: [(BDI)GaBn₂], [(BDI)Ga(NHDMP)₂] (DMP = 2,6-Me₂C₆H₃), [(BDI)Ga(NHDIPP)₂] (DIPP = 2,6-iPr₂C₆H₃), [(BDI)Ga(PHPh)₂] were examined for their reactivity towards the α-proton elimination mechanism for the formation of multiple bonds that is observed in transition metals. All of these complexes were shown to be unreactive towards α-proton elimination. The di-substituted β-diketiminato-gallium complex [(BDI)GaMe₂] was subjected to various aniline derivatives to investigate if the methyl ligands exhibited the same reactivity as di-methyl transition metal complexes, where the methyl ligands could deprotonate the aniline to form a metal-imido complex. This complex was found to have no reactivity with anilines. The mono-substituted β-diketiminato-gallium complex [(BDI)Ga(NHDMP)Cl] was tested for its reactivity with ⁿBuLi to abstract the amide proton and eliminate LiCl to form a gallium imido complex. While the ¹H NMR spectrum of the reaction mixture showed that a reaction had occurred, the products could not be isolated for characterisation. Another mono-substituted β-diketiminato-gallium complex [(BDI)Ga(PHPh)Cl] was also tested for its reactivity with ⁿBuLi to abstract the phosphide proton and eliminate LiCl to form a gallium phosphinidene complex. The ¹H NMR spectrum and ³¹P NMR spectrum of the isolated complex revealed that it still contained a phosphide proton, however the gallium centre now appeared to be bonded to a former methine carbon of an isopropyl group of the BDI ligand (fig 32). This bond may have formed through metathesis between an intermediate containing a gallium-phosphorus double bond, and the C-H bond of the isopropyl group. Further mechanistic studies could confirm if an intermediate such as [fig 3] is formed, and the synthetic strategy altered to isolate it. The synthesis of β-diketiminato-gallium-alkoxide complexes was also attempted, however the products of these synthesises could not be isolated due to solubility issues, potentially due to polymerisation.</p>

The Synthesis of Novel Gallium Carbenes, Nitrenes, Phosphinidenes and Alkoxides

<p>In the present study, synthetic routes to formal double bonds between gallium and carbon (fig 1), nitrogen (fig 2), and phosphorus (fig 3) have been investigated. These synthetic routes utilised the monoanionic, four electron donor, β-diketiminate (BDI) ligand to provide both steric and electronic stabilisation to three coordinate gallium complexes. The known di-substituted β-diketiminatogallium complexes: [(BDI)GaMe₂] and [(BDI)Ga(NHPh)₂], as well the new complexes: [(BDI)GaBn₂], [(BDI)Ga(NHDMP)₂] (DMP = 2,6-Me₂C₆H₃), [(BDI)Ga(NHDIPP)₂] (DIPP = 2,6-iPr₂C₆H₃), [(BDI)Ga(PHPh)₂] were examined for their reactivity towards the α-proton elimination mechanism for the formation of multiple bonds that is observed in transition metals. All of these complexes were shown to be unreactive towards α-proton elimination. The di-substituted β-diketiminato-gallium complex [(BDI)GaMe₂] was subjected to various aniline derivatives to investigate if the methyl ligands exhibited the same reactivity as di-methyl transition metal complexes, where the methyl ligands could deprotonate the aniline to form a metal-imido complex. This complex was found to have no reactivity with anilines. The mono-substituted β-diketiminato-gallium complex [(BDI)Ga(NHDMP)Cl] was tested for its reactivity with ⁿBuLi to abstract the amide proton and eliminate LiCl to form a gallium imido complex. While the ¹H NMR spectrum of the reaction mixture showed that a reaction had occurred, the products could not be isolated for characterisation. Another mono-substituted β-diketiminato-gallium complex [(BDI)Ga(PHPh)Cl] was also tested for its reactivity with ⁿBuLi to abstract the phosphide proton and eliminate LiCl to form a gallium phosphinidene complex. The ¹H NMR spectrum and ³¹P NMR spectrum of the isolated complex revealed that it still contained a phosphide proton, however the gallium centre now appeared to be bonded to a former methine carbon of an isopropyl group of the BDI ligand (fig 32). This bond may have formed through metathesis between an intermediate containing a gallium-phosphorus double bond, and the C-H bond of the isopropyl group. Further mechanistic studies could confirm if an intermediate such as [fig 3] is formed, and the synthetic strategy altered to isolate it. The synthesis of β-diketiminato-gallium-alkoxide complexes was also attempted, however the products of these synthesises could not be isolated due to solubility issues, potentially due to polymerisation.</p>

Rubesanolides F and G: Two Novel Lactone-Type Norditerpenoids from Isodon rubescens

A phytochemical investigation of the leaves of the medicinal plant Isodon rubescens led to the isolation of the two new degraded abietane lactone diterpenoids rubesanolides F (1) and G (2). Their structures were elucidated based on the analyses of the HRESIMS and 1D/2D NMR spectral data, and their absolute configurations were determined by ECD spectrum calculations and X-ray single crystal diffraction methods. Compounds 1 and 2, with a unique γ-lactone subgroup between C-8 and C-20, were found to form a carbonyl carbon at C-13 by removal of the isopropyl group in an abietane diterpene skeleton. Rubesanolide G (2) is a rare case of abietane that possesses a cis-fused configuration between rings B and C. The two isolates were evaluated for their biological activities against two cancer cell lines (A549 and HL60), three fungal strains (Candida alba, Aspergillus niger and Rhizopus nigricans) and three bacterial strains (Escherichia coli, Staphylococcus aureus and Bacillus subtilis).

Organic synthesis and anti-influenza A virus activity of cyclobakuchiols A, B, C, and D

Novel antiviral agents for influenza, which poses a substantial threat to humans, are required. Cyclobakuchiols A and B have been isolated from Psoralea glandulosa, and cyclobakuchiol C has been isolated from P. corylifolia. The structural differences between cyclobakuchiol A and C arise due to the oxidation state of isopropyl group, and these compounds can be derived from (+)-(S)-bakuchiol, a phenolic isoprenoid compound present in P. corylifolia seeds. We previously reported that bakuchiol induces enantiospecific anti-influenza A virus activity involving nuclear factor erythroid 2-related factor 2 (Nrf2) activation. However, it remains unclear whether cyclobakuchiols A–C induce anti-influenza A virus activity. In this study, cyclobakuchiols A, B, and C along with cyclobakuchiol D, a new artificial compound derived from cyclobakuchiol B, were synthesized and examined for their anti-influenza A virus activities using Madin-Darby canine kidney cells. As a result, cyclobakuchiols A–D were found to inhibit influenza A viral infection, growth, and the reduction of expression of viral mRNAs and proteins in influenza A virus-infected cells. Additionally, these compounds markedly reduced the mRNA expression of the host cell influenza A virus-induced immune response genes, interferon-β and myxovirus-resistant protein 1. In addition, cyclobakuchiols A–D upregulated the mRNA levels of NAD(P)H quinone oxidoreductase 1, an Nrf2-induced gene, in influenza A virus-infected cells. Notably, cyclobakuchiols A, B, and C, but not D, induced the Nrf2 activation pathway. These findings demonstrate that cyclobakuchiols have anti-influenza viral activity involving host cell oxidative stress response. In addition, our results suggest that the suitably spatial configuration between oxidized isopropyl group and phenol moiety in the structure of cyclobakuchiols is required for their effect.

Antiproliferative, Antimicrobial and Antiviral Activity of β-Aryl-δ-iodo-γ-lactones, Their Effect on Cellular Oxidative Stress Markers and Biological Membranes

The aim of this work was the examination of biological activity of three selected racemic cis-β-aryl-δ-iodo-γ-lactones. Tested iodolactones differed in the structure of the aromatic fragment of molecule, bearing isopropyl (1), methyl (2), or no substituent (3) on the para position of the benzene ring. A broad spectrum of biological activity as antimicrobial, antiviral, antitumor, cytotoxic, antioxidant, and hemolytic activity was examined. All iodolactones showed bactericidal activity against Proteus mirabilis, and lactones 1,2 were active against Bacillus cereus. The highest cytotoxic activity towards HeLa and MCF7 cancer cell lines and NHDF normal cell line was found for lactone 1. All assessed lactones significantly disrupted antioxidative/oxidative balance of the NHDF, and the most harmful effect was determined by lactone 1. Contrary to lactone 1, lactones 2 and 3 did not induce the hemolysis of erythrocytes after 48 h of incubation. The differences in activity of iodolactones 1–3 in biological tests may be explained by their different impact on physicochemical properties of membrane as the packing order in the hydrophilic area and fluidity of hydrocarbon chains. This was dependent on the presence and type of alkyl substituent. The highest effect on the membrane organization was observed for lactone 1 due to the presence of bulky isopropyl group on the benzene ring.

Crystal structure of N,N-diisopropyl-4-methylbenzenesulfonamide

The synthesis of the title compound, C13H21NO2S, is reported here along with its crystal structure. This compound crystallizes with two molecules in the asymmetric unit. The sulfonamide functional group of this structure features S=O bond lengths ranging from 1.433 (3) to 1.439 (3) Å, S—C bond lengths of 1.777 (3) and 1.773 (4) Å, and S—N bond lengths of 1.622 (3) and 1.624 (3) Å. When viewing the molecules down the S—N bond, the isopropyl groups are gauche to the aromatic ring. On each molecule, two methyl hydrogen atoms of one isopropyl group are engaged in intramolecular C—H...O hydrogen bonds with a nearby sulfonamide oxygen atom. Intermolecular C—H...O hydrogen bonds and C—H...π interactions link molecules of the title compound in the solid state.

Fast photothermal poly(NIPAM-co-β-cyclodextrin) supramolecular hydrogel with self-healing through host–guest interaction for intelligent light-controlled switches

A graphene oxide/poly(N-isopropylacrylamide-co-β-cyclodextrin) (GO/poly(NIPAM-co-β-CD)) hydrogel has been synthesized through host–guest interaction between β-cyclodextrin (β-CD) and the isopropyl group of N-isopropylacrylamide (NIPAM).

Study of Intermolecular Interactions of Binary Mixture of sec- and tert-Amines with Alkanols (C1-C3): Refractive Indices

In this work, the refractive indices (nD) of binary mixture of diisopropylamine (DIPA) and tributylamine (TBA) (as sec- and tert-amines) with alkanol (methanol, ethanol, 1-propanol, 2-propanol) were measured from 298.15 K to 318.15 K. The sec- and tert-amines were selected to study the effect of branching at N-atom of amine on intermolecular interactions with alkanols having different chain length. It was found that the TBA interacts strongly with alkanol in comparison to DIPA due to steric hindrance offered by isopropyl group at N-atom. Various mixing rules were applied to evaluate the refractive index compared well with the experimental refractive indices data for the present binary mixtures. The experimental refractive indices was also fitted to Redlich-Kister polynomial.