Synthesis and properties of (2-pyridyl)alkylamine- and (2-pyridyl)alkylamine–amide-coordinated copper(II) complexes: Structures and non-covalent interactions

Reaction of the ligand N-methyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylethyl)amine (mpppa) with equimolar amounts of [Cu(H₂O)₆][ClO₄]₂ or CuCl₂ · 2H₂O in MeCN afforded mononuclear copper(II) complexes [Cu(mpppa)][ClO₄]₂ (1) and [Cu(mpppa)Cl₂] (2). Crystal structure analysis reveals CuN₃O (two pyridyl, an aliphatic amine, and an amide oxygen) coordination in 1 and CuN₃Cl₂ (two pyridyl, an aliphatic amine, and two chlorides) coordination in 2. Crystal packing diagram of 1 reveals that one of the perchlorate counteranions provides weak coordination to copper(II) centers and in turn the copper(II) centers assume pseudo-six-coordination, generating 1D chain. Notably, one of the copper(II)-coordinated chloride ions in 2 participates in an intramolecular N–H?Cl interaction. Intermolecular C–H?Cl interactions in the solid state generate helical structure. Spectroscopic (IR, UV–Vis, and EPR) and redox properties of the two complexes have been investigated and compared.     

β-Glucosidase 2 (GBA2) Activity and Imino Sugar Pharmacology

β-Glucosidase 2 (GBA2) is an enzyme that cleaves the membrane lipid glucosylceramide into glucose and ceramide. The GBA2 gene is mutated in genetic neurological diseases (hereditary spastic paraplegia and cerebellar ataxia). Pharmacologically, GBA2 is reversibly inhibited by alkylated imino sugars that are in clinical use or are being developed for this purpose. We have addressed the ambiguity surrounding one of the defining characteristics of GBA2, which is its sensitivity to inhibition by conduritol B epoxide (CBE). We found that CBE inhibited GBA2, in vitro and in live cells, in a time-dependent fashion, which is typical for mechanism-based enzyme inactivators. Compared with the well characterized impact of CBE on the lysosomal glucosylceramide-degrading enzyme (glucocerebrosidase, GBA), CBE inactivated GBA2 less efficiently, due to a lower affinity for this enzyme (higher K_I) and a lower rate of enzyme inactivation (k_inact). In contrast to CBE, N-butyldeoxygalactonojirimycin exclusively inhibited GBA2. Accordingly, we propose to redefine GBA2 activity as the β-glucosidase that is sensitive to inhibition by N-butyldeoxygalactonojirimycin. Revised as such, GBA2 activity 1) was optimal at pH 5.5–6.0; 2) accounted for a much higher proportion of detergent-independent membrane-associated β-glucosidase activity; 3) was more variable among mouse tissues and neuroblastoma and monocyte cell lines; and 4) was more sensitive to inhibition by N-butyldeoxynojirimycin (miglustat, Zavesca®), in comparison with earlier studies. Our evaluation of GBA2 makes it possible to assess its activity more accurately, which will be helpful in analyzing its physiological roles and involvement in disease and in the pharmacological profiling of monosaccharide mimetics.     

Rhodium(III) cis-dihydrido complexes with 3,6-bis(2′-pyridyl)pyridazine (dppn) and bidiazines. Crystal and molecular structure of [Rh(H)2(dppn)(PPh3)2]PF6· CH2Cl2

The acetone complex [Rh(H)₂(acetone)₂(PPh₃)₂]- PF₆ reacts with bidiazines and 3,6-bis(2′-pyridyl)- pyridazine (dppn) giving the air stable cis-dihydrido rhodium(III) [Rh(H)₂(L)(PPh₃)₂]PF₆ complexes. The structure of the dichloromethane solvate of [Rh(H)₂(dppn)(PPh₃)₂]PF₆ has been determined by X-ray crystal structure analysis. Crystals are monoclinic, space group P2₁/a, with a = 18.629(6), b = 15.339(5), c = 17.146(5) Å, β = 101.02(3)° and Z = 4. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by block-matrix least-squares to R = 0.076 for 6225 observed reflections. In the structure discrete [Rh(H)₂(dppn)(PPh₃)₂]⁺ cationic complexes, PF₆⁻ anions and dichloromethane solvent molecules are present. The Rh atom is octahedrally surrounded by two cis hydride ligands and by two cis nitrogen atoms from a dppn molecule acting as a bidentate chelating ligand through two neighbouring pyridyl and pyridazinyl nitrogen atoms. Two P atoms from PPh₃, ligands in trans apical positions complete to octahedral the coordination of Rh.     

Preparation of (±)-2-(2,3-2H2)Jasmonic Acid and Its Methyl Ester,Methyl (±)-2-(2,3-2H2)Jasmonate

For use as the internal standards in a quantitative analysis of natural jasmonic acid (JA) and methyl jasmonate (JAMe) by gas chromatography-mass spectrometry-selected ion monitoring, (±)-2-(2,3–²H₂)JA and its methyl ester, (±)-2-(2,3–²H₂)JAMe, were efficiently prepared from 2-(2–pentyl)-2-cyclopentenone through catalytic semi-deuteriogenation of acetylenic intermediates with deuterium gas in pyridine.     

Synthesis of (2′S)-1-(2-C-Azidomethyl-2-deoxy and 2-C-Cyanomethyl-2-deoxy-β-D-arabinofuranosyl)cytosines

Abstract

2′-C-Cyanomethyl-2′-deoxy-arabinosylcytosine 3 and 2′-C-azidomethyl-2′-deoxy-arabinosylcytosine 4 were synthesized from uridine. The antineoplastic activities of these compounds were evaluated.     

Physicochemical and biological properties of 2-O-α-D-galactosyl-cyclomaltohexaose (α-cyclodexterin) and -cyclomaltoheptaose (β-cyclodextrin)

The physicochemical and biological properties of the new branched cyclomaltooligosaccharides (cyclodextrins; CDs), 2-O-α-D-galactosyl-cyclomaltohexaose (2-O-α-D-galactosyl-α-cyclodextrin, 2-Gal-αCD) and 2-O-α-D-galactosyl-cyclomaltoheptaose (2-O-α-D-galactosyl-β-cyclodextrin, 2-Gal-βCD), were investigated. The formation of inclusion complexes of 2-Gal-CDs with various kinds of guest compounds (clofibrate, cholesterol, cholecalciferol, digitoxin, digitoxigenin, and prostaglandin A(1)) was examined by a solubility method, and the results were compared with those of non-branched CDs and other 6-O-glycosyl-CDs such as 6-O-α-D-galactosyl-CDs, 6-O-α-D-glucosyl-CDs, and 6-O-α-maltosyl-CDs. The inclusion abilities of 2-Gal-αCD for clofibrate and prostaglandin A(1), and 2-Gal-βCD for clofibrate, cholecalciferol, cholesterol, and digitoxigenin were markedly weaker than those of non-branched CD and other 6-O-glycosyl-CDs in each series, probably because of a steric hindrance caused by the α-(1→2)-galactoside linkage. The hemolytic activities of 2-Gal-CDs on human erythrocytes were the lowest among each CD series, and the compounds showed negligible cytotoxicity towards Caco-2 cells up to at least 100mM.     

5-(2-Pyrrolidinyl)oxazolidinones and 2-(2-pyrrolidinyl)benzodioxanes: Synthesis of all the stereoisomers and α4β2 nicotinic affinity

The four stereoisomers of 2-oxazolidinone 5-substituted with 1-methyl-2-pyrrolidinyl (1), of 1,4-benzodioxane 2-substituted with the same residue (2) and of the nor-methyl analogue of this latter (2a) were synthesized as candidate nicotinoids. Of the 12 compounds, two N-methylated pyrrolidinyl-benzodioxane stereoisomers, namely those with the same relative configuration at the pyrrolidine stereocentre as (S)-nicotine, bind at α4β2 nicotinic acetylcholine receptor with submicromolar affinity. Consistently with the biological data, docking analysis enlightens significant differences in binding site interactions not only between 1 and 2, but also between 2 and 2a and between the stereoisomers of 2 accounting for the critical role played, in the case of the pyrrolidinyl-benzodioxanes, by the chirality of both the stereolabile and stereostable stereogenic atoms, namely the protonated tertiary nitrogen and the two asymmetric carbons.     

9-(2-Deoxy-ß-D-xylofuranosyl)adenine and 1-(2-Deoxy-ß-D-xylofuranosyl)thymine: Phosphorylation and Stability

Abstract

Phosphorylation of 1-(2-deoxy-β-D-xylofuranosyl)thymine (1) or 9-(2-deoxy-β-D-xylofuranosyl)adenine (3) with phosphoryl chloride gives the cyclic 3′,5′-phosphates (2 and 4a) but not the 5′-monophosphates 8a or 8b. The latter are obtained by phosphorylation of the 3′-0-benzoylated 2′-deoxy-β-D-xylonucleosides (7a, b) and subsequent base-catalyzed removal of the benzoyl groups. Compound 3, as the parent dA, depurinates in acidic medium, a reaction which is facilitated in the case of the N⁶-benzoyl derivative 9b and reduced after the introduction of an amidine protecting group. N-Glycosylic bond hydrolysis of 2′-deoxy-β-D-xylofuranosyl nucleosides is enhanced by a factor of two compared to 2′-deoxy-β-D-ribofuranosyl nucleosides.     

Resonance Raman studies of the peroxotitanate(IV) complexes K2(Ti(O2)(SO4)2)·5H2O and K2(Ti(O2)(C2O4)2)·3H2O

The resonance Raman spectra of K₂(Ti(O₂)(SO₄)₂)·5H₂O and K₂(Ti(O₂)(C₂O₄)₂)·3H₂O are recorded. The results are consistent with the triangular structure of the peroxotitanium unit, Ti(O₂), with C_2ν symmetry. The ν(OO), ν_s(TiO) and ν_as(TiO) are observed around 890, 610 and 535 cm⁻¹, respectively. The resonance effects are shown to be associated with the 425 nm absorption band. This band is assigned to the O₂²⁻ → Ti(IV) charge-transfer transition. The calculated force constant values for the O₂²⁻ and TiO bonds are 320 and 275 N m⁻¹, respectively.     

Stereoselective Synthesis of 1- and 2-O-α-d-Cellotriosyl-3-deoxy-2(R)- and 2(S)-glycerols Related to Rhynchosporoside

The stereoselective synthesis of 1- and 2-O-α-d-cellotriosyl-3-deoxy-2(R)- and 2(S)-glycerols, which determined the structure of rhynchosporoside produced by Rhynchosporium secalis, and their phytotoxicity toward the host plant (Hordeum vulgare) are described in detail.     

Combination of Azidothymidine (AZT) and (E)-5-(2-Bromovinyl)-2′-deoxyuridine (BVDU) Inhibits the Replication of Herpes Simplex Virus Type 1 (HSV-1) and Type 2 (HSV-2) and Varicella Zoster Virus (VZV) Strains That Are Deficient in the Expression of the Viral Thymidine Kinase (tk)

Abstract

Combinations of high concentrations of AZT with BVDU, acyclovir (ACV) or ganciclovir (GCV) show antagonism against TK⁺ HSV-1, but not TK⁺ VZV strains, in cell cultures. When BVDU and AZT were used in combination against TK^? HSV-1, TK^? HSV-2 and TK^? VZV strains, a pronounced inhibition of viral replication was observed. This potentiating effect was not seen if AZT was combined with ACV or GCV.     

Niemann–Pick C2 (NPC2) and intracellular cholesterol trafficking

Cholesterol is an important precursor for numerous biologically active molecules, and it plays a major role in membrane structure and function. Cholesterol can be endogenously synthesized or exogenously taken up via the endocytic vesicle system and subsequently delivered to post-endo/lysosomal sites including the plasma membrane and the endoplasmic reticulum. Niemann–Pick C (NPC) disease results in the accumulation of exogenously-derived cholesterol, as well as other lipids, in late endosomes and lysosomes (LE/LY). Identification of the two genes that underlie NPC disease, NPC1 and NPC2, has focused attention on the mechanisms by which lipids, in particular cholesterol, are transported out of the LE/LY compartment. This review discusses the role of the NPC2 protein in cholesterol transport, and the potential for concerted action of NPC1 and NPC2 in regulating normal intracellular cholesterol homeostasis.     

Stereospecific Synthesis and Anti-HIV Activity of (Z)2′- and (E)3′-Deoxy-2′(3′)-C-(chloromethylene) Pyrimidine Nucleosides

Abstract

Reaction of 1-[2,5(and 3,5)-di-O-trityl-β-D-erythro-pentofuran-3 (and 2)-ulosyl]uracil derivatives 5 and 6 with (chloromethyl)triphenylphosphorane resulted in the stereoselective formation of (E)-3′- and (Z)-2′-chloromethylene derivatives 7 (69%) and 8 (53%), respectively, deprotection of which gave 9 and 10. Transformation of the uracil nucleoside 7 into cytosine one followed by deprotection yielded 12. The latter was converted into the arabinoside 14. The fully deprotected chloromethylene nucleosides were tested for their activity against HIV-1 and HIV-2.     

2′-(E)-O-p-coumaroylgalactaric acid and 2′-(E)-O-feruloylgalactaric acid in citrus

2′-(E)-O-p-Coumaroyl- and 2′-(E)-O-feruloylgalactaric acids, hitherto unknown in nature, have been isolated and identified from orange peel.     

Synthesis of 7-(tetrahydropyran-2-yl)- and 7-(4-acetoxytetrahydropyran-2-yl)-ε-rhodomycinone and 7-(tetrahydropyran-2-yl)-ε-pyrromycinone

The ¹³C.n.m.r spectra of water-soluble and -insoluble glucans synthesized by enzymes isolated from six strains of Streptococcus mutans are interpreted. The glucans are shown to be composed primarily of α(1→3)- and α-(1→6)-linked glucosyl residues, and the relative abundance of each linkage is estimated from peak areas. Treatment of water-insoluble glucans with dextranase is found to result in water-soluble and -insoluble products, the former enriched in α-(1→6)-linkages and the latter in α-(1→3)-linkages. The structural conclusions arrived at by ¹³C-n.m.r. spectroscopy are consistent with data from methylation analysis and ¹H-n.m.r. spectroscopy.     

Disturbed brain phospholipid and docosahexaenoic acid metabolism in calcium-independent phospholipase A(2)-VIA (iPLA(2)β)-knockout mice

Calcium-independent phospholipase A(2) group VIA (iPLA(2)β) releases docosahexaenoic acid (DHA) from phospholipids in vitro. Mutations in the iPLA(2)β gene, PLA2G6, are associated with dystonia-parkinsonism and infantile neuroaxonal dystrophy. To understand the role of iPLA(2)β in brain, we applied our in vivo kinetic method using radiolabeled DHA in 4 to 5-month-old wild type (iPLA(2)β(+/+)) and knockout (iPLA(2)β(-/-)) mice, and measured brain DHA kinetics, lipid concentrations, and expression of PLA(2), cyclooxygenase (COX), and lipoxygenase (LOX) enzymes. Compared to iPLA(2)β(+/+) mice, iPLA(2)β(-/-) mice showed decreased rates of incorporation of unesterified DHA from plasma into brain phospholipids, reduced concentrations of several fatty acids (including DHA) esterified in ethanolamine- and serine-glycerophospholipids, and increased lysophospholipid fatty acid concentrations. DHA turnover in brain phospholipids did not differ between genotypes. In iPLA(2)β(-/-) mice, brain levels of iPLA(2)β mRNA, protein, and activity were decreased, as was the iPLA(2)γ (Group VIB PLA(2)) mRNA level, while levels of secretory sPLA(2)-V mRNA, protein, and activity and cytosolic cPLA(2)-IVA mRNA were increased. Levels of COX-1 protein were decreased in brain, while COX-2 protein and mRNA were increased. Levels of 5-, 12-, and 15-LOX proteins did not differ significantly between genotypes. Thus, a genetic iPLA(2)β deficiency in mice is associated with reduced DHA metabolism, profound changes in lipid-metabolizing enzyme expression (demonstrating lack of redundancy) and of phospholipid fatty acid content of brain (particularly of DHA), which may be relevant to neurologic abnormalities in humans with PLA2G6 mutations.