ESI／MS of N-（O, O-Diisopropyl） Phosphoryl Aromatic Amino Acids and their Stability Investigation Using HPLC／UV／ESI／MS

The full scan ESI/MS and ESI/MS^2 of N-(O, O-diisopropyl) phosphoryl aromatic amino acids (DIPPAAAs), N-(O, O-diisopropyl) phosphoryl phenylalanine, N-(O, O-diisopropyl)phosphoryl tryptophan and N-(O, O-diisopropyl) phosphoryl tyrosine, were obtained. The specific ions for them were found. Their stability in the LC mobile phase was investigated using developed HPLC/UV/ESI/MS and the results demonstrated that the DIPPAAAs were stable in the mobile phase (5 mmol/L NH4Ac-MeCN (80:20,v/v, pH7.5) within 48 h.     

Protonation and Dehydrogenation During the Multiphoton Ionization of the Cluster: C_4H_5N(H_2O)_n

Proton transfer process in hydrogen-bonded clusters has attracted great interest of many chemists in physical chemistry and biochemistry1-5. Pyrrole (C4H5N) is one of the building blocks of some important biomolecules6. And pyrrole is a compound of five-membered hetero-cyclic aromatic ring, in which a lone pair of electrons offered by the N atom and the two double bonds form a delocalized big ( bond. In this paper we report on the observations for the cluster system pyrrole-water by use of a…     

Photoaddition of N-substituted piperazines to C60: an efficient approach to the synthesis of water-soluble fullerene derivatives

An oxidative radical photoaddition of mono N-substituted piperazines to [60]fullerene was systematically investigated. Reactions of C60 with piperazines bearing bulky electron-withdrawing groups (2-pyridyl, 2-pyrimidinyl) were found to be the most selective and yielded C60(amine)4O as major products along with small amounts of C60(amine)2. In contrast, interactions of fullerene with N-methylpiperazine and N-(tert-butoxycarbonyl)piperazine were found to have low selectivity due to different side reactions. Tetraaminofullerene derivative C60(N-(2-pyridyl)piperazine)4O was found to react readily with organic and inorganic acids to yield highly water-soluble salts (solubility approximately 150 mg mL(-1)). In contrast, C60(N-(2-pyrimidinyl)piperazine)4O undergoes hydrolysis under the same conditions and results in a complex mixture of compounds with an average composition of C60(N-(2-pyrimidinyl)piperazine)2(OH)2O. Radical photoaddition of N-(2-pyridyl)piperazine to fullerene derivatives can be used as a facile route for their transformation into water-soluble compounds. Two model fullerene cycloadducts (a methanofullerene and a pyrrolidinofullerene) were easily converted into mixtures of regioisomers of A=C60(N-(2-pyridyl)piperazine)4O (A=cyclic addend) that give highly water-soluble salts under acid treatment.     

Energetics of the manganese oxide cluster cations Mn(N)O+ (N = 2-5): role of oxygen in the binding of manganese atoms

The photodissociation of manganese oxide cluster cations Mn(N)O+ (N = 2-5), into Mn(N-1)O+ (one-atom loss) and Mn(N-2)O+ (two-atom), was investigated in the photon-energy range of 1.08-2.76 eV. The bond-dissociation energies D0(Mn(N-1)O+...Mn) for N = 3, 4, and 5 were determined to be 1.84+/-0.03, 0.99+/-0.05, and 1.25+/-0.14 eV, respectively, from the threshold energies for the one- and two-atom losses. As Mn2O+ did not dissociate even at the highest photon energy used, the bond dissociation energy of Mn2O+, D0(Mn+...MnO), was obtained from a density-functional-theory calculation to be 3.04 eV. The present findings imply that the core ion Mn2O+ is bound weakly with the rest of the manganese atoms in Mn(N)O+.     

Identification of self-assembly products from N-phosphoamino acids by electrospray ionization mass spectrometry

The self-assembly products of N-(O,O'-diisopropyl)-L-alpha-amino acids in aqueous media, N-(O,O'-diisopropyl)phosphoryl dipeptides and tripeptides, were identified by electrospray ionization mass spectrometry. A stepwise fragmentation of the [M + H](+) ions from the C-terminus of N-phosphopeptides was observed. Copyright 2000 John Wiley & Sons, Ltd.     

Interaction between N-Phospho-Amino Acids and Nucleoside in Aqueous Medium

Thebiosynthesisofnucleicacid,oneofthemostimportantbio-macromolecules,isahighlyelegantprocess,whichinvolvestheparticipationofmanyenzymesandenergycarriers,suchasATP',whilechemicalsynthesisofoligonucleotidesgenerallyinvolvescomplicatedprotectinganddeprotectingprocesses'.Inthepreviouswork,nucleotidesandoligonucleotidesweredirectlyformedacthereaction,,-ofN-(O,O-diisopropyl)phosphorylthreonineanduridineinanhydrouspyridine'.SoN-(O,O-diisopropyl)phospho-aminoacid(DIPP-aa)wasproposedasamodelcompou…     

VINYL RADICAL POLYMERIZATION INITIATED WITH CERIC ION AND N-(SUBSTITUTED PHENYL) ACETAMIDE SYSTEMS

The polymerization of acrylamide (AAM)in H_2O/DMF or in H_2O/CH_3CN mixed solvent initiated with ceric ion (Ce~(4+) )/N-(substituted phenyl)-acetamide systems have been studied. The redox polymerization was revealed by the low value of overall activation energy (E_α) of AAM polymerization using ceric ion/N-(substituted phenyl) acetamide system as an initiator. The end group of polymer formed was detected by IR spectrum analysis method, it revealed the presence of N-(m-acetoxy-methylphenyl) acetamide (m-AAe) moiety end group in the polymer obtained with ceric ion/m-AAe initiation system.     

Bioisostere of Sulfonyl Moiety-The Synthesis of New ALS Inhibitors N-(Asymmetry Disubstituted Phosphoryl)-N'-(4,6-dimethoxypyrimidin-2-yl) Ureas

IntroductionAcetolactatesynthase(ALS)isthefirstcommonenzymeinthebiosyntheticpathwayforthebranched-chainaminoacidsvaline,leucineandisoleucine.Itisaveryeffectivetargetsiteforherbicidalaction,whichistheselectedmodeofactionasitisspecificforplantsanddoesnotaffectmammals.Sulfonylureaherbicidesareanewclassofherbicidesdiscoveredinthemid-l97O'sl.ItsmodeofactionhasbeenestablishedtobeinhibitorytowardALS2.Muchattentionhasbeenfocusedonthiskindofcompounds,sincetheyhaveexcellentactivity,ahighdegreeofseIe…     

N-对R苯基氮杂15冠5八钼多酸钠超分子配合物的合成与结构

为研究大环化合物对客体分子的选择性, 合成了通式为[NaL(Et2O)]2Na2Mo8O26的三种新型N-对R苯基氮杂15冠5八钼多酸钠超分子配合物(其中L分别为: N-苯基氮杂15冠5、N-对氯苯基氮杂15冠5和N-对甲苯基氮杂15冠5), 进行了元素分析, 红外光谱与核磁共振等结构参数的表征, 对R基为CH3的标题配合物作了X射线四圆衍射测定, 该晶体属单斜晶系, 空间群为P21/a,a=1.4590(4)nm, b=1.3817(3)nm, c=1.7639(5)nm, β=112.67(2)°, V=3.281(1)nm^3, Mr=2021.3, Dc=2.11g/cm^3,μ=2.37mm^-^1, F(000)=2048, R=0.045和Rw=0.057, 与[Na.(DB18C6)(CH3OH)M6O19和[Na(DB24C8)]2M6O19进行比较,结果表明: 大环化合物不仅对客体金属离子有分子识别性, 而且对与之抗衡的多酸阴离子也具有影响。     

Promoting effect of ethanol on the synthesis of N-（2-methylphenyl）-hydroxylamine from o-nitrotoluene in Zn/H2O/CO2 system

The promoting effect of ethanol on the synthesis of N-（2-methylphenyl）hydroxylamine from o-nitrotoluene in Zn/H₂O/CO₂ system was observed.By adding appropriate amount of ethanol,the selectivity of N-（2-methylphenyl）hydroxylamine increased from 71%to 90%when the reduction was carried out at 25℃under normal pressure of CO₂.     

Synthesis and structural characterization of 1- and 2-substituted indazoles: ester and carboxylic acid derivatives

A series of indazoles substituted at the N-1 and N-2 positions with ester-containing side chains -(CH2)(n)CO2R of different lengths (n = 0-6, 9, 10) are described.Nucleophilic substitution reactions on halo esters (X(CH2)(n)CO2R) by 1H-indazole inalkaline solution lead to mixtures of N-1 and N-2 isomers, in which the N-1 isomer predominates. Basic hydrolysis of the ester derivatives allowed the synthesis of the corresponding indazole carboxylic acids. All compounds were fully characterised by multinuclear NMR and IR spectroscopies, MS spectrometry and elemental analysis; the NMR spectroscopic data were used for structural assignment of the N-1 and N-2 isomers.The molecular structure of indazol-2-yl-acetic acid (5b) was determined by X-ray diffraction, which shows a supramolecular architecture involving O2-H...N1 intermolecular hydrogen bonds.     

Vibrational relaxation of CN stretch of pseudo-halide anions (OCN-, SCN-, and SeCN-) in polar solvents

The vibrational relaxation dynamics of pseudo-halide anions XCN- (X = O, S, Se) in polar solvents were studied to understand the effect of charge on solute-to-solvent intermolecular energy transfer (IET) and solvent assisted intramolecular vibrational relaxation (IVR) pathways. The T1 relaxation times of the CN stretch in these anions were measured by IR pump/IR probe spectroscopy, in which the 0-1 transition was excited, and the 0-1 and 1-2 transitions were monitored to follow the recovery of the ground state and decay of the excited state. For these anions in five solvents, H2O, D2O, CH3OH, CH3CN, and (CH3)2SO, relaxation rates followed the trend of OCN- > SCN- > SeCN-. For these anions and isotopes of SCN-, the relaxation rate was a factor of a few (2.5-10) higher in H2O than in D2O. To further probe the solvent isotope effect, the relaxation rates of S12C14N-, S13C14N-, and S12C15N- in deuterated methanols (CH3OH, CH3OD, CH3OH, CD3OD) were compared. Relaxation rate was found to be affected by the change of solvent vibrational band at the CN- stretching mode (CD3 symmetric stretch) and lower frequency regions, suggesting the presence of both direct IET and solvent assisted IVR relaxation pathways. The possible relaxation pathways and mechanisms for the observed trends in solute and solvent dependence were discussed.     

Design and preparation of a novel fluorescent naphthalimide derivative supramolecular self-assembly system and its bioimaging application

ABSTRACT

A novel fluorescent naphthalimide derivative gelator (N-18) was designed and characterised which could form a stable gel in 1,4-dioxane/H₂O (2/1, v/v), methyl sulfoxide (DMSO), ethanol/H₂O (4/1, v/v), acetone/H₂O (2/1, v/v) and methanol. The self-assembly process of molecule N-18 in the five solvents was carefully investigated by the field emission scanning electron microscope, UV-vis absorption spectra, fluorescence emission spectra, fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and water contact angle experiments. Different structures from microbelts to helical nanofibers were formed in the self-assembly process. Hydrogen bonding and π–π stacking interaction were the mainly driving forces for the formation of gel. At the same time, the hydrophobic surface with the contact angles of 133°–142° was observed on the xerogel films N-18 from the above five solvents. Interestingly, molecule N-18 could be applied in bioimaging in a living cell.     

A family of oxorhenium(v) complexes incorporating chelated monoanionic ONN reduced Schiff base and dianionic ONNO tetradentate ligands: synthesis, spectroscopic and electrochemical studies

The green colored complexes of the type Re(V)O(L(SB))Cl(2), 1, have been synthesised by reacting NBu(4)[ReOCl(4)] with HL(SB) in dry ethanol. Here, L(SB)(-) are the deprotonated forms of N-(2-hydroxybenzyl)-2-picolylamine (HL(SB)(1)); N-(2-hydroxybenzyl)-N',N'-dimethylethylenediamine (HL(SB)(2)) and N-(2-hydroxybenzyl)-N',N'-diethylethylenediamine (HL(SB)(3)). Similarly, NBu(4)[ReOCl(4)] reacted with N,N-bis(2-hydroxybenzyl)-2-picolylamine (H(2)L(1)); N,N-bis(2-hydroxybenzyl)-N',N'-dimethylethylenediamine (H(2)L(2)); N,N-bis(2-hydroxybenzyl)-N',N'-diethylethylenediamine (H(2)L(3)); [N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)]-2-aminoethanol (H(2)L(4)); [N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)]-2-methyl-2-amino-1-propanol (H(2)L(5)); N,N-bis(1-hydroxyethyl)-2-picolylamine (H(2)L(6)), to give the monochloro complexes Re(V)O(L)Cl, 2. The X-ray structures of the complexes are reported. The molecular structures observed in the solid state are preserved in solution ((1)H NMR). In acetonitrile solution the Re(V)O(L)Cl, 2, display a one-electron couple, Re(VI)O(L)Cl(+)-Re(V)O(L)Cl, near 1.0 V vs SCE. The electrogenerated hexavalent complexes [Re(VI)O(L)Cl]ClO(4), 3, are paramagnetic and display sextet EPR spectra in solution at room temperature (A(av) approximately 417 (G), g approximately 1.914).     

Theoretical Study of the Sensitivity-Improvement Effect of Phosphoryl Group in Mass Spectrometry of Small Peptides

Mass spectrometry plays an important role in peptide sequencing since the invention of soft ionization techniques, such as fast atom bombardment (FAB), electrospray (ESI) and matrix-assisted laser desorption/ionization (MALDI). In our previous work, it was found that phosphorylation on the N-terminal of small peptides could enormously improve their sensitivity in FAB-MS1.To understand the sensitivity-improvement effect of phosphoryl group, the energies for the protonation of glycylglycin…     

Synthesis and Crystal Structure of (C6N3H18)2Ti4O4(C2O4)7·4H2O

The title compound (C6N3H18)2Ti4O4(C2O4)7(4H2O 1 (C13H22N3O18Ti2, Mr = 604.14) was synthesized by the reaction of Ti(SO4)2, H2C2O4(2H2O and N-(2-ammonioethyl)- piperazinium (AEPP) in aqueous solution. The single-crystal X-ray analysis has revealed that 1 crystallizes in the triclinic system, space group Pī with a = 9.1437(6), b = 11.4991(10), c = 11.6975(8)A, α = 96.2915(18), β = 107.998(3), γ = 104.276(4)°, V = 1110.35(14)A3, Z = 2, Dc = 1.807 g/cm3, F(000) = 618, μ = 0.815 mm－1, the final R = 0.0463 and wR = 0.1264 for 3718 observed reflections with I > 2σ(I). X-ray crystal-structure analysis suggests that compound 1 consists of [Ti4O4(C2O4)7]6－ anion and two protonated N-(2-ammonioethyl)piperazinium cations. The anions are linked into an infinite chain through Ti4O4(C2O4)8 by sharing the oxalates as bridging ligands.     

Enantiospecific inclusion of chiral 1,2-dichloroethane rotamers in the crystal lattice of chiral square-pyramidal Cu(II) complexes with perfectly polar alignment of guest and host molecules

The inclusion compounds, [CuL(1)2(H2O)].(P)-C2H4Cl2 and [CuL(2)2(H2O)].(M)-C2H4Cl2(HL1 = N-(2-hydroxy-5-nitrobenzyl)-(R)-alpha-methylbenzylamine and HL2 = N-(2-hydroxy-5-nitrobenzyl)-(S)-alpha-methylbenzylamine), crystallise in the non-centrosymmetric space group C2; intermolecular hydrogen bonding leads to a perfectly polar alignment of both host and guest molecules with enantioselectivity.     

Synthesis and Crystal Structure of (C_6N_3H_(18))_2Ti_4O_4(C_2O_4)_7·4H_2O

1 INTRODUCTION The open-framework inorganic materials have been synthesized before the early 1980s[1]. Parti- cularly, metal phosphates have been investigated widely during the past few years[2, 3]. In recent years, considerable efforts have been devote…     

Lithium complexes supported by amine bis-phenolate ligands as efficient catalysts for ring-opening polymerization of L-lactide

Lithium complexes bearing dianionic amine bis(phenolate) ligands are described. Reactions of ligand precursors H(2)O(2)NN(Me), H(2)O(2)NN(Py) or H(2)O(2)NO(Me) [H(2)O(2)NN(Me)=Me(2)NCH(2)CH(2)N-(CH(2)-2-HO-3,5-C(6)H(2)((t)Bu)(2))(2); H(2)O(2)NN(Py)=(2-C(5)H(4)N)CH(2)N-(CH(2)-2-HO-3,5-C(6)H(2)((t)Bu)(2))(2); H(2)O(2)NO(Me)=MeOCH(2)CH(2)N-(CH(2)-2-HO-3,5-C(6)H(2)((t)Bu)(2))(2)] with 2.2 molar equivalents of (n)BuLi in diethylether afford (Li(2)O(2)NN(Me))(2) (1), (Li(2)O(2)NN(Py))(2) (2) and (Li(2)O(2)NO(Me))(2) (3) as tetra-nuclear lithium complexes. The crystalline solids of partially hydrolyzed product, (LiO(HO)NN(Py)) (4), were obtained from recrystallization of 2 in diethylether solution for three months. The synthesis of (LiO(HO)NO(Me))(2) (5) was carried out at ambient temperature by carefully layering a solution of water in hexane on top of a solution of 3 in Et(2)O. Crystalline solids of were obtained after two months. Molecular structures are reported for compounds 1, 3, 4 and 5. Compounds 1-3 show excellent catalytic activities toward the ring-opening polymerization of L-lactide in the presence of benzyl alcohol.     

A convenient route to N-[2-(Fmoc)aminoethyl]glycine esters and PNA oligomerization using a Bis-N-Boc nucleobase protecting group strategy

A simple and practical synthesis of the benzyl, allyl, and 4-nitrobenzyl esters of N-[2-(Fmoc)aminoethyl]glycine is described starting from the known N-(2-aminoethyl)glycine. These esters are stored as stable hydrochloride salts and were used in the synthesis of peptide nucleic acid monomers possessing bis-N-Boc-protected nucleobase moieties on the exocyclic amino groups of ethyl cytosin-1-ylacetate, ethyl adenin-9-ylacetate and ethyl (O(6)-benzylguanin-9-yl)acetate. Upon ester hydrolysis, the corresponding nucleobase acetic acids were coupled to N-[2-(Fmoc)aminoethyl]glycine benzyl ester or to N-[2-(Fmoc)aminoethyl]glycine allyl ester in order to retain the O(6) benzyl ether protecting group of guanine. The Fmoc/bis-N-Boc-protected monomers were successfully used in the Fmoc-mediated solid-phase peptide synthesis of mixed sequence 10-mer PNA oligomers and are shown to be a viable alternative to the currently most widely used Fmoc/Bhoc-protected peptide nucleic acid monomers.