Search results for "Aryl"

Strong Influence of the Ancillary Ligand over the Photodynamic Anticancer Properties of Neutral Biscyclometalated IrIII Complexes Bearing 2-Benzoazol…

2018

In this paper, the synthesis, comprehensive characterization and biological and photocatalytic properties of two series of neutral IrIII biscyclometalated complexes of general formula [Ir(C^N)2(N^O)], where the N^O ligands are 2‐(benzimidazolyl)phenolate‐N,O (L1, series a) and 2‐(benzothiazolyl)phenolate‐N,O (L2, series b), and the C^N ligands are 2‐(phenyl)pyridinate or its derivatives, are described,. Complexes of types a and b exhibit dissimilar photophysical and biological properties. In vitro cytotoxicity tests conclusively prove that derivatives of series a are harmless in the dark against SW480 cancer cells (colon adenocarcinoma), but express enhanced cytotoxicity versus the same cel…

Synthesis of 1,3-bis(trimethylcyclam) and 1,3-bis(trimethylcyclen) substituted benzenes

2009

Pd-catalyzed amination of 1,3-dibromobenzene with N,N',N''-trimethylcyclam and N,N',N''-trimethylcyclen provided corresponding 1,3-bis(tetraazamacrocyclic) derivatives of benzene in 25-32% yields. The dependence of the products yields on the phosphine ligand applied (BINAP, DavePHOS) as well as on the stoichiometry of starting compounds was established. Scope and limitations for the synthesis of N-phenyl and N-(3-bromophenyl) derivatives of trimethylcyclam and trimethylcyclen were demonstrated.

Effects of Remote Ligand Substituents on the Structures, Spectroscopic, and Magnetic Properties of Two-Coordinate Transition-Metal Thiolate Complexes

2018

The first-row transition-metal(II) dithiolates M(SAriPr4)2 [AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2; M = Cr (1), Mn (3), Fe (4), Co (5), Ni (6), and Zn (7)] and Cr(SArMe6)2 [2; ArMe6 = C6H3-2,6-(C6H2-2,4,6-Me3)2] and the ligand-transfer reagent (NaSAriPr4)2 (8) are described. In contrast to their M(SAriPr6)2 (M = Cr, Mn, Fe, Co, Ni, and Zn; AriPr6 = C6H3-2,6-(C6H2-2,4,6-iPr3)2) congeners, which differ from 1 and 3-6 in having p-isopropyl groups on the flanking aryl rings of the terphenyl substituents, compounds 1 and 4-6 display highly bent coordination geometries with S-M-S angles of 109.802(2)° (1), 120.2828(3)° (4), 91.730(3)° (5), and 92.68(2)° (6) as well as relatively close metal-flanking …

Total Synthesis of (-)-Oxycodone via Anodic Aryl-Aryl Coupling.

2019

A fully regio- and diastereoselective electrochemical 4a–2′-coupling of a 3′,4′,5′-trioxygenated laudanosine derivative enables the synthesis of the corresponding morphinandienone. This key intermediate is further transformed into (−)-oxycodone through conjugate nucleophilic substitution for E-ring closure and [4 + 2] cycloaddition with photogenerated singlet oxygen to accomplish diastereoselective hydroxylation at C-14. The anodic transformation provides high yields and can be performed under constant current conditions both in a simple undivided cell or in continuous flow.

Unexpected Scholl Reaction of 6,7,13,14-Tetraarylbenzo[k]tetraphene: Selective Formation of Five-Membered Rings in Polycyclic Aromatic Hydrocarbons

2016

Cyclodehydrogenation is a versatile reaction that has enabled the syntheses of numerous polycyclic aromatic hydrocarbons (PAHs). We now describe a unique Scholl reaction of 6,7,13,14-tetraarylbenzo[k]tetraphene, which "unexpectedly" forms five-membered rings accompanying highly selective 1,2-shift of aryl groups. The geometric and optoelectronic nature of the resulting bistetracene analogue with five-membered rings is comprehensively investigated by single-crystal X-ray, NMR, UV-vis absorption, and cyclic voltammetry analyses. Furthermore, a possible mechanism is proposed to account for the selective five-membered-ring formation with the rearrangement of the aryl groups, which can be ration…

Melatonin in the seasonal response of the aphid Acyrthosiphon pisum.

2018

Aphids display life cycles largely determined by the photoperiod. During the warm long-day seasons, most aphid species reproduce by viviparous parthenogenesis. The shortening of the photoperiod in autumn induces a switch to sexual reproduction. Males and sexual females mate to produce overwintering resistant eggs. In addition to this full life cycle (holocycle), there are anholocyclic lineages that do not respond to changes in photoperiod and reproduce continuously by parthenogenesis. The molecular or hormonal events that trigger the seasonal response (i.e., induction of the sexual phenotypes) are still unknown. Although circadian synthesis of melatonin is known to play a key role in verteb…

2021

Although insect herbivores are known to evolve resistance to insecticides through multiple genetic mechanisms, resistance in individual species has been assumed to follow the same mechanism. While both mutations in the target site insensitivity and increased amplification are known to contribute to insecticide resistance, little is known about the degree to which geographic populations of the same species differ at the target site in a response to insecticides. We tested structural (e.g., mutation profiles) and regulatory (e.g., the gene expression of Ldace1 and Ldace2, AChE activity) differences between two populations (Vermont, USA and Belchow, Poland) of the Colorado potato beetle, Lepti…

Ocean Acidification and the Loss of Phenolic Substances in Marine Plants

2012

Rising atmospheric CO(2) often triggers the production of plant phenolics, including many that serve as herbivore deterrents, digestion reducers, antimicrobials, or ultraviolet sunscreens. Such responses are predicted by popular models of plant defense, especially resource availability models which link carbon availability to phenolic biosynthesis. CO(2) availability is also increasing in the oceans, where anthropogenic emissions cause ocean acidification, decreasing seawater pH and shifting the carbonate system towards further CO(2) enrichment. Such conditions tend to increase seagrass productivity but may also increase rates of grazing on these marine plants. Here we show that high CO(2) …

Allium istanbulense, a new autumnal species of A. sect. Codonoprasum (Amaryllidaceae) from Turkey and its taxonomic position among allied species

2018

Allium istanbulense, a new species of Allium sect. Codonoprasum, is described and illustrated from Istanbul surroundings (European Turkey). It is a late-flowering diploid species (2n = 16), occurring in the undergrowth of oak or pine woods mainly on sandy or incoherent soils. Its morphology, karyology, leaf anatomy, seed micromorphology, ecology, conservation status and taxonomic relationships are examined. A taxonomic comparison with the most allied late flowering species of sect. Codonoprasum and identification keys of the group are also provided.

Arabidopsis thaliana nicotianamine synthase 4 is required for proper response to iron deficiency and to cadmium exposure.

2013

International audience; The nicotianamine synthase (NAS) enzymes catalyze the formation of nicotianamine (NA), a non-proteinogenic amino acid involved in iron homeostasis. We undertook the functional characterization of AtNAS4, the fourth member of the Arabidopsis thaliana NAS gene family. A mutant carrying a T-DNA insertion in AtNAS4 (atnas4), as well as lines overexpressing AtNAS4 both in the atnas4 and the wild-type genetic backgrounds, were used to decipher the role of AtNAS4 in NA synthesis, iron homeostasis and the plant response to iron deficiency or cadmium supply. We showed that AtNAS4 is an important source for NA. Whereas atnas4 had normal growth in iron-sufficient medium, it dis…