A novel chiral oxazoline copper(II)-based complex inhibits ovarian cancer growth in vitro and in vivo by regulating VEGF/VEGFR2 downstream signaling pathways and apoptosis factors

A novel chiral oxazoline copper(II)-based complex {[Cu(C13H14NO3S)2]}2 (Cu-A) was synthesized by an in situ reaction using L-methioninol, 4-hydroxyisophthalaldehyde, sodium hydroxide and copper(II) nitrate trihydrate as reactants. Its crystal structure was characterized. In vitro, Cu-A was superior to cis-dichlorodiammineplatinum (DDP) in cytotoxicity and angiogenesis inhibition. Cu-A significantly induced apoptosis of ovarian cancer cells (SKOV3) and human umbilical vein endothelial cells (HUVECs), showing significant anti-ovarian cancer and anti-angiogenesis effects. Notably, Cu-A significantly inhibits the growth of ovarian cancer in nude mice xenografted with SKOV3 cells, and it is less renal toxic than DDP. The molecular mechanism of anti-ovarian cancer and anti-angiogenesis is possibly that it down-regulates the expression of the proteins ERK1/2, AKT, FAK, and VEGFR2 and their phosphorylated proteins p-ERK1/2, p-AKT, p-FAK, and p-VEGFR2 in the VEGF/VEGFR2 signal transduction pathway to inhibit SKOV3 cell and HUVEC proliferation, induce apoptosis, suppress migration and metastasis, and inhibit angiogenesis. What's more, Cu-A significantly inhibits ovarian tumor growth in vivo by inhibiting tumor cells from inducing vascular endothelial cells to form their own vasculature and by inhibiting the expression of the anti-apoptotic protein Bcl-2 and up-regulating the expression of the pro-apoptotic proteins Caspase-9 and Bax to induce apoptosis of tumor cells.

Microwave-assisted rapid synthesis of chiral oxazolines

Chiral oxazoline compounds play an extremely important role in asymmetric synthesis and drug discovery. Herein a simpler, greener and more efficient microwave-assisted protocol to rapidly access chiral oxazolines is developed using aryl nitriles or cyano-containing compounds and chiral β-amino alcohols as starting materials. The reaction proceeds smoothly in the presence of a recoverable heterogeneous catalyst in either concentrated solution or under solvent-free conditions. The advantages of this method include rapidness, convenience, environmental protection, high atom economy, and excellent yields. The protocol should find wider application in the community in the future.

Synthesis and crystal structures of tetra-meric [2-(4,4-dimethyl-2-oxazolin-2-yl)anilido]sodium and tris-[2-(4,4-dimethyl-2-oxazolin-2-yl)anilido]ytterbium(III)

Reaction of 2-(4,4-dimethyl-2-oxazolin-2-yl)aniline (H2-L1) with one equivalent of Na[N(SiMe3)2] in toluene afforded pale-yellow crystals of tetra-meric poly[bis-[μ3-2-(4,4-dimethyl-2-oxazolin-2-yl)anilinido][μ2-2-(4,4-dimethyl-2-oxa-zolin-2-yl)aniline]tetra-sodium(I)], [Na4(C11H13N2O)4] n or [Na4(H-L1)4] n (2), in excellent yield. Subsequent reaction of [Na4(H-L1)4] n (2) with 1.33 equivalents of anhydrous YbCl3 in a 50:50 mixture of toluene-THF afforded yellow crystals of tris-[2-(4,4-dimethyl-2-oxazolin-2-yl)anilinido]ytterbium(III), [Yb(C11H13N2O)3] or Yb(H-L1)3 (3) in moderate yield. Direct reaction of three equivalents of 2-(4',4'-dimethyl-2'-oxazolin-yl)aniline (H2-L1) with Yb[N(SiMe3)2]3 in toluene resulted in elimination of hexa-methyl-disilazane, HN(SiMe3)2, and produced Yb(H-L1)3 (3) in excellent yield. The structure of 2 consists of tetra-meric Na4(H-L1)4 subunits in which each Na+ cation is bound to two H-L1 bridging bidentate ligands and these subunits are connected into a polymeric chain by two of the four oxazoline O atoms bridging to Na+ cations in the adjacent tetra-mer. This results in two 4-coordinate and two 5-coordinate Na+ cations within each tetra-meric unit. The structure of 3 consists of a distorted octa-hedron where the bite angle of ligand L1 ranges between 74.72 (11) and 77.79 (11) degrees. The oxazoline (and anilide) N atoms occupy meridional sites such that for one ligand an anilide nitro-gen is trans to an oxazoline nitro-gen while for the other two oxazoline N atoms are trans to each other. This results in a significantly longer Yb-N(oxazoline) distance [2.468 (3) Å] for the bond trans to the anilide compared to those for the oxazoline N atoms trans to one another [2.376 (3), 2.390 (3) Å].

Unusual rearrangement of an N-heterocyclic carbeneviaa ring-opening and ring-closing process

The reaction of a pentadentate NHC ligand precursor with Ni(OAc)₂·4H₂O or Pd(OAc)₂in the presence of a base yields four-coordinate square-planar Ni(ii) and Pd(ii) complexes with an unusual ligand generatedin situ.

Chiral oxazoline ligands with two different six-membered azaheteroaromatic rings – synthesis and application in the Cu-catalyzed nitroaldol reaction

Synthesis and catalytic activity of chiral ligands 5,6-diphenyl-3-{3-[(4S/R)-4-R/Ar-4,5-dihydro-1,3-oxazol-2-yl]pyridin-2-yl}amino-1,2,4-triazines 2 and their analogs 3 possessing an N-oxide function in the pyridine ring are described. The pivotal step in the synthesis of ligands 2 is the Buchwald-Hartwig Pd-catalyzed cross-coupling reaction between 3-bromo-5,6-diphenyl-1,2,4-triazine (7a) and enantiopure 3-(4,5-dihydro-1,3-oxazol-2-yl)pyridin-2-amines 6a–d. Aromatic nucleophilic substitution of chlorine in 3-chloro-5,6-diphenyl-1,2,4-triazine (7b) with 3-(4,5-dihydro-1,3-oxazol-2-yl)pyridin-2-amine 1-oxides 12 was investigated as the key reaction in the synthesis of ligands 3. Two undesired derivatives 13 or 14, resulting from unexpected reactions of 3, were isolated depending on reaction conditions. Compounds 2 and 3 as well as the side products 13 and 14 were screened as chiral ligands in the copper catalyzed enatioselective nitroaldol reaction.

Structural characterization of copper complexes with chiral 1,2,4-triazine-oxazoline ligands

The crystal structure determination of oxazoline-1,2,4-triazine ligand

Regioselective Pd-Catalyzed Synthesis of 2,3,6-Trisubstituted Pyridines from Isoxazolinones

Substituted pyridines are prevalent heterocycles of fundamental importance. Their efficient regioselective preparation is often still a challenge despite a large number of reported synthetic methodologies. In this letter we report an operationally simple approach that makes use of readily accessible isoxazolinones. The protocol involves a Pd(II)-catalyzed C-regioselective 1,4-addition to vinylketones, followed by a Pd(0)-catalyzed transformation, which is assumed to proceed via vinylnitrene-Pd intermediates. Both hydrogen and air are necessary for the pyridine formation step and could be employed at ratios above the upper explosive limit thus avoiding a safety issue. This new strategy allows an effective, scalable and practical access to various previously unknown 2,3,6-trisubstituted pyridines.

N-{2-[(4S)-4-tert-Butyl-4,5-dihydro-1,3-oxazol-2-yl]phen-yl}-5,6-diphenyl-1,2,4-triazin-3-amine

The title compound, C(28)H(27)N(5)O, was synthesized using palladium cross-coupling amination of 3-bromo-5,6-diphenyl-1,2,4-triazine with 2-[(4S)-4-tert-butyl-4,5-dihydro-1,3-oxazol-2-yl]aniline. The oxazoline ring is almost planar, with a maximum atomic deviation of 0.023 (5) Å. The phenyl rings make dihedral angles of 29.0 (1) and 54.6 (1)° with the triazine ring while the benzene ring makes a dihedral angle of 0.6 (1)° with the oxazoline ring. The conformation of the mol-ecule is influenced by strong intra-molecular N-H⋯N and weak C-H⋯N hydrogen bonds. In the crystal, screw-axis related mol-ecules are linked into supra-molecular chains by inter-molecular C-H⋯O hydrogen bonds. π-π stacking is observed between the oxazoline and triazine rings of adjacent mol-ecules, with a centroid-centroid distance of 3.749 (2) Å.