Simple, nitrogen-rich, energetic salts of 5-nitrotetrazole

A new family (ammonium, 1, hydrazinium, 2, guanidinium, 3, aminoguanidinium, 4, diamino-guanidinium, 5, and triaminoguanidinium, 6) of simple, nitrogen-rich energetic salts based on 5-nitro-2 H-tetrazole (HNT) were synthesized. In addition, the hemihydrate of 1 (1a) and the hydrate of 6 (6a) were also isolated. In all cases, stable salts were obtained and fully characterized by vibrational (IR, Raman) spectroscopy, multinuclear ((1)H, (13)C and (14)N) NMR spectroscopy, mass spectrometry, elemental analysis, and X-ray structure determination. Compounds 1and 2 crystallize in the monoclinic space group P2 1/c, 1a and 3 crystallize in C/2 c, 4 in P2 1/n, 5 in P2 1, 6 in orthorhombic P2 12 12 1, and 6a in triclinic P1. Initial safety testing (impact, friction, and electrostatic sensitivity) and thermal stability measurements (DSC) were also carried out. The NT salts all exhibit good thermal stabilities (decomposition above 150 degrees C). The constant volume energies of combustion (Delta c U(exp)) of 1-6 were experimentally determined by oxygen bomb calorimetry to be -1860(30) cal/g ( 1), -1770(30) cal/g ( 1a), -2110(150) cal/g (2), -2250(40) cal/g ( 3), -2470(30) cal/g (4), -2630(40) cal/g (5), -2690(50) cal/g (6), and -2520(50) cal/g (6a). Because of the significant experimental uncertainties obtained in these measurements, their validity was checked by way of quantum chemical calculation (MP2) of electronic energies and an approximation of lattice enthalpy. The predicted constant volume energies of combustion (Delta c U(pred)) calculated by this method were -2095.9 cal/g (1), -1975.7 cal/g ( 1a), -2362.4 cal/g (2), -2526.6 cal/g (3), -2654.6 cal/g (4), -2778.6 cal/g ( 5), -2924.0 cal/g (6), and -2741.4 cal/g ( 6a). From the experimentally determined density, chemical composition, and energies of formation (back calculated from the heats of combustion) the detonation pressures and velocities of 1 (7950 m/s, 23.9 GPa), 1a (7740 m/s, 22.5 GPa), 2(8750 m/s, 30.1 GPa), 3 (7500 m/s, 20.1 GPa) 4(8190 m/s, 24.7 GPa), 5(8230 m/s, 24.4 GPa), 6 (8480 m/s, 26.0 GPa) and 6a (7680 m/s, 20.7 GPa) were predicted using the EXPLO5 code.     

The hydrogen bonding and amino-imino tautomerization of the alkoxy-aminopyridines and amino-methoxypyrimidines with acetic acid The effects of the methoxy group

The hydrogen bonding and amino-imino tautomerization of the systems of 2-amino-3-methoxypyridine (2A3MOP), 2-amino-6-methoxypyridine (2A6MOP), 2-amino-6-n-propoxypyridine (2A6NPOP), 2-amino-6-iso-propoxypyridine(2A6IPOP), 2-amino-4-methoxypyrimidine (2A4MOPM), 4-amino-2-methoxypyrimidine (4A2OPM), 4-amino-6-methoxypyrimidine (4A6MOPM), 2-amino-4-methoxy-6-methylpyrimidine (MMPM), and 2-amino-4,6-dimethoxypyrimidine (DMOPM), with acetic acid (AcOH) in n-hexane at room temperature were investigated by means of the UV absorption and fluorescence spectroscopy. From the UV absorption spectra the presence of the dual hydrogen-bonded complexes that linked by a 1:1 molar ratio with AcOH were found, since the enthalpy changes accompanying the hydrogen bond formation between 2A3MOP, 2A4MOPM, 4A2MOPM, 4A6MOPM, or MMPM, and AcOH were ca. 42.8-61.1kJmol(-1) in n-hexane. The fluorescence spectra of the 2A3MOP/AcOH, 2A4MOPM/AcOH, 4A6MOPM/AcOH, and MMPM/ AcOH systems revealed that the imino-tautomers were produced through double proton transfer in the amino hydrogen-bonded 1:1 complexes in the S1 state, but the imino-tautomer formation for the 4A2MOPM/AcOH system was not found on account of the steric hindrance due to the inversion of the methoxy group in the S1 state. The imino-tautomer for the MMPM/AcOH system fluoresces most intensely among these systems investigated. On the other hand, not only the formation of the corresponding amino dual hydrogen-bonded complex and but also that of imino-tautomer were prevented for the 2A6MOP/AcOH, 2A6NPOPM/AcOH, 2A6IPOP/AcOH, and DMOPM/AcOH systems, because of the steric hindrance of the methoxy group in both the S0 and S1 states. The theoretical approaches by an ab initio molecular orbital calculation were in accord with the experimental results.     

A new glycoside from the leaves of Neoalsomitra integrifoliola

A new ionone glycoside （6R,9R）-blumenyl α-L-rhamnopyranosyl-（1 → 6）-β-D-gluco-pyranoside （1）, together with a new natural product 2-methoxyl-4-trans-pmpenyl-phenol α-L-rhamnopyranosyl-（1 → 6）-β-D-glucopyranoside （2）, was isolated from the leaves ofNeoalsomitra integrifoliola. Their structures were elucidated by chemical and spectral analysis. Compound 1 showed weak anti-inflammatory and low-level antioxidant activities.     

Comparative study of some synthesised and commercial fluorogenic substrates for horseradish peroxidase and its mimetic enzyme hemin by a flow injection method

Four 3,4-dihydroquinoxalin-2(1H)-one derivatives, i.e., 3,4-dihydroquinoxalin-2(lH)-one (DHQ), 3-methyl-3,4-dihydroquinoxalin-2(1H)-one (MDHQ), 3,4-dihydroquinoxalin-2(1H)-one-6-acid (DHQ-6-A) and 3-methyl-3,4-dihydroquinoxalin-2(1H)-one-6-acid (MDHQ-6-A), and N,N′-dicyanomethyl-o-phenylenediamine (DCM-OPA) were synthesised as potential substrates for horseradish peroxidase (HRP). Of these compounds DCM-OPA, DHQ and MDHQ can be prepared by very simple methods in a pure form in large quantities. Their properties for use as fluorogenic substrates for HRP and its mimetic enzyme hemin were compared with commercially available substrates, i.e., p-hydroxyphenylacetic acid (p-HPA), p-hydroxyphenylpropionic acid (p-HPPA), homovanillic acid (HVA) and tyramine, by a flow injection method. The results showed that DCM-OPA and MDHQ were the best among the five synthesised substrates and p-HPPA and p-HPA are better than HVA and tyramine. Substrates p-HPPA, p-HPA, DCM-OPA and MDHQ showed comparable ability for H₂O₂ detection in HRP and hemin catalysed reaction systems, with detection limits in the nmol l⁻¹ region. The stability of DCM-OPA is better than MDHQ, but both are stable for at least a month in a refrigerator.     

The quinones of bicyclo[3.1.0]hexatriene: A computational study of their chemistry and thermochemistry

Quinones of bicyclo[3.1.0]hexa-1,3,5-triene were examined computationally. The six compounds considered were the five possible classical and one non-classical quinone: bicyclo[3.1.0]hexa-1(6),4-diene-2,3-dione (and its monocyclic isomer with a long trans-annular bond), bicyclo[3.1.0]hexa-1(5),3-diene-2,6-dione, bicyclo[3.1.0]hexa-1,4-diene-3,6-dione (and its monocyclic isomer with a long trans-annular bond), and bicyclo[3.1.0]hexa-1(5),4-diene-2,4-dione-3,6-diyl, a non-classical (non-Kekulé) zwitterion. The two long trans-annular bond structures are akin to that found for m-benzyne. Geometries were calculated (BLYP/6-31G¹, CASSCF(2,2)/6-31G¹, MP2/6-31G¹) and electronic structural inferences were made from the geometries. Also calculated were relative energies and heats of formation (CBS-QB3), singlet and triplet energies (BLYP/6-31G¹), and ionization energies and electron affinities (HF/6-311+G⁷//BLYP/6-31G¹). The NICS(1) calculations were performed as a probe of the aromaticity of the diverse quinones.     

Characterization of the conformational probability of N-acetyl-phenylalanyl-NH2 by RHF, DFT, and MP2 computation and AIM analyses, confirmed by jet-cooled infrared data

Computational and experimental determinations were carried out in parallel on the conformational probability of N-Acetyl-Phenylalanine-NH2 (NAPA). Ab initio computations were completed at the BLYP/6-311G(df,p), B3LYP/6-31G(d), B3LYP/6-31G(d,p), and B3LYP/6-31+G(d) levels of theory, labeled L/61fp, B/6, B/6p, and B/6+, respectively. Three experimentally identified conformers were compared with theoretical data, confirming their identities as the betaLanti, gammaLgauche+, and gammaLgauche- (BACKBONESIDECHAIN) conformers. Evidence comes from matching experimental and theoretical data for all three constituent N-H stretches of NAPA, with a Delta(Experimental-Theoretical) = approximately 1-3 cm(-1), approximately 0-5 cm(-1), and approximately 1-6 cm(-1), at the L/61fp and B/6+ levels, respectively. Corrected-ZPE relative energies were computed to be 0.14, 0.00, 0.26 and 0.00, 0.67, 0.57 (kcal*mol(-1)) for the betaLanti, gammaLgauche+, and gamma(Lgauche- conformers, respectively, at the L/61fp and B/6+ levels, respectively. The MP2/6-31+G(d) level of theory was subsequently found to give similar relative energies. Characterization of the intramolecular interactions responsible for red and blue shifting of the N-H stretches showed the existence of the following intramolecular interactions: C=O[i]- - -HN[i], (Ar[i])-Cgamma- - -HN[i+1], (Ar[i])-Cdelta-H- - -O=C[i-1] for betaLanti; C=O[i-1]- - -HN[i+1], (Ar[i])-Cgamma- - -HN[i+1], (Ar[i])-C-H- - -O=C[i] for gammaLgauche+; and C=O[i-1]- - -HN[i+1] for gammaLgauche-. Each of these interactions were further investigated and subsequently characterized by orbital population and Atoms-In-Molecules (AIM) analyses, with the identity of overlap and bond critical points (BCP) serving as 'scoring criteria', respectively. Experimental and theoretical carbonyl stretches were also compared and showed good agreement, adding further strength to the synergy between experiment and theory.     

Anion-free bambus[6]uril and its supramolecular properties

Methods for the preparation of anion-free bambus[6]uril (BU6) are presented. They are based on the oxidation of iodide anion, which is bound inside the macrocycle, utilizing dark oxidation by hydrogen peroxide or photooxidation in the presence of titanium dioxide. Anion-free BU6 was found to be insoluble in any of the investigated solvents; however, it dissolves in methanol/chloroform (1:1) or acetonitrile/water (1:1) mixtures in the presence of the tetrabutylammonium salt of a suitable anion. The association constants with halide ions, BF(4)(-), NO(3)(-), and CN(-), were measured by (1)H NMR spectroscopy. The highest association constant (8.9×10(5) M(-1)) was found for the 1:1 complex of BU6 with I(-) in acetonitrile/water mixture. A number of crystal structures of BU6 complexes with various anions were obtained. The influence of the anion size on the macrocycle diameter is discussed together with an unusual arrangement of the macrocycles into separate layers.     

New Half-sandwich Zirconium（IV） Complexes Containing Salicylaldimine Ligands： Synthesis,Characterizations and Catalytic Properties

Two new half-sandwich zirconium（IV） complexes bearing salicylaldimine ligands of the type Cp＊Zr[2-tBu-4-R-6-（CH=NiPr）C6H2O]C12[R=H（1）, tBu（2）] were prepared by the reaction of Cp＊ZrC13 with the corresponding lithium of salicylaldimine ligands 2-tBu-4-R-6-（CH=NiPr）C6H2OLi[R=H（LiLa）, tBu（LiLb）]. Com- plexes 1 and 2 were characterized by 1H NMR, BC NMR spectroscopy and elemental analysis. When activated with AliBu3 and Ph3CB（C6F5）4, both complexes 1 and 2 exhibited reasonable catalytic activities for ethylene polymeriza- tion, producing polyethylenes with moderate molecular weight. Complexes 1 and 2 also exhibited reasonable catalyt- ic activities for ethylene copolymerization with 1-hexene, producing poly（ethylene-co-l-hexene）s with moderate molecular weight and reasonable 1-hexene content.     

Quantitative determination of marine toxins associated with diarrhetic shellfish poisoning by liquid chromatography coupled with mass spectrometry

Quantitative determination by liquid chromatography (LC) coupled with mass spectrometry (MS) was achieved for the following 10 toxins found in association with diarrhetic shellfish poisoning: okadaic acid (OA), dinophysistoxin-1 (DTX1), 7-O-palmitoylokadaic acid (palOA), 7-O-palmitoyldinophysistoxin-1 (pa1DTX1), pectenotoxin-1 (PTX1), pectenotoxin-2 (PTX2), pectenotoxin-2 seco acid (PTX2SA), pectenotoxin-6 (PTX6), yessotoxin (YTX), and 45-hydroxyyessotoxin (YTXOH). Toxins in 2 g of the adductor muscle or the digestive glands of scallops, Patinopecten yessoensis, were extracted with 18 ml of methanol-water (9:1, v/v), freed of polar contaminants by partition between chloroform and water, and treated by solid-phase extraction on a silica cartridge column. Samples containing YTXOH were purified separately on a buffered reversed-phase column. Chromatographic separation was achieved by the following combinations of columns and mobile phases: a Symmetry C18 column with acetonitrile-0.05% acetic acid (7:3, v/v) for OA, DTX1, PTX6 and PTX2SA; a Develosil ODS column with the same mobile phase for PTX1 and PTX2; a Capcellpak column with methanol-2.5% acetic acid (98:2, v/v) for palOA and palDTX1; and an Inertsil ODS column with methanol-0.2 M ammonium acetate (8:2, v/v) for YTX and YTXOH. Carboxylic acid toxins were selectively monitored on [M-H]- ions, sulfated toxins on [M-Na]-ions, and neutral toxins on [M+NH4]+ ions. Average recoveries of the toxins spiked to tissue homogenates ranged from 70 to 134%. Detection limits in the muscle ranged from 5 to 40 ng/g and those in the digestive glands from 10 to 80 ng/g.     

N-nitroso- and N-nitraminotetrazoles

N-Nitroso- (5a,c) and N-nitraminotetrazoles (6a-c) were synthesized from the corresponding aminotetrazoles (3a-c) either by the direct nitration with acetic anhydride/HNO3 or by dehydration of the corresponding nitrates (4a-c) with concentrated sulfuric acid. The conversion of the N-nitrosoaminotetrazoles (5a,c) with peroxytrifluoroacetic acid (CF3CO3H) yielded the corresponding nitramines in high yield (6a (82%), 6c (80%)). The N-nitroso- (5a,c) and N-nitraminotetrazoles (6a-c) have been fully characterized by vibrational (IR, Raman) and multinuclear NMR spectroscopy (14N/15N, 1H, 13C), mass spectrometry, and elemental analysis. A detailed discussion of the 15N chemical shifts and 1H-15N coupling constants is given. The molecular structures in the solid state were determined by single-crystal X-ray diffraction (3a,c; 5a,c; 6a-c) and a detailed discussion of the molecular structures will be presented. Furthermore, the structure and bonding as well as N,N rotational barriers are discussed on the basis of theoretically obtained data (B3LYP/6-31G(d,p), NBO analysis). In the case of two N-nitraminotetrazoles (6a,c) the physicochemical properties (e.g., D, P, delta(f)H degrees) were evaluated. The heat of formation was calculated to be positive for 6a and 6c (+2.8 and +85.2 kcal mol(-1), respectively) and the calculated detonation velocity with 5988 (6a) and 7181 (6c) m s(-1) reaches values of TNT and nitroglycerin.     

柄型金属有机化合物(Ⅳ)——四甲基二硅桥连取代环戊二烯基钛和锆化合物的合成及催化乙烯聚合

四甲基二硅桥连取代环戊二烯基配体相继与丁基锂及MCl₄·2THF作用,生成四甲基二硅桥连取代环戊二烯基钛和锆化合物(Me₂SiSiMe₂)(C₅H₄R)(C₅H₄R')MCl₂[R=H,R'=t-Bu,M=Ti(1),Zr(2),Hf(3);R=H,R'=Me,M=Ti(4);R=R'=Me,M=Ti(5),Zr(6)].通过元素分析、MS和¹HNMR谱表征了化合物的分子结构,并通过X射线衍射分析测定了化合物1的晶体结构.研究了在甲基铝氧烷(MAO)的助催化下,化合物1-3和6对乙烯聚合的催化性能。     

A new eremophilanolide from Senecio sinuatus Gilib

From the hexane extracts of Senecio sinuatus roots, the new 3beta-angeloyloxy-6beta-hydroxyeremophil-1(10)-en-8beta,12-olide (3), along with the known compounds 3beta-angeloyloxy-6beta-hydroxyeremophil-1(10)-ene (1), 3beta-senecioyloxy-6beta-hydroxyeremophil-1(10)-ene (2), and 3beta-angeloyloxy-6beta,8alpha-dihydroxyeremophil-1(10)-en-8beta,12-olide (4), were isolated. Complete 1H and 13C NMR chemical shift assignments of 1-4 were achieved using one- and two-dimensional NMR techniques, including gHMQC and gHMBC experiments. A Monte Carlo search, followed by B3LYP/6-31G*DFT calculation, provided the theoretical conformations of the eremophilane rings, which were in agreement with results derived from 1H-1H NMR coupling constant analysis, and confirmed by NOESY experiments.     

Detecting pM concentrations of prostaglandins in cell culture supernatants by capillary SCX-LC-MS/MS

A highly sensitive, improved online strong cation exchange (SCX)--RP capillary liquid chromatographic (cLC) method with IT mass spectrometric (IT-MS/MS) detection for the simultaneous determination of prostaglandin (PG)A(1), PGD(2), PGE(1), PGE(2), PGF(2alpha), 8-iso-(8i)PGF(2alpha), 6-keto-(6k)PGF(1alpha), and 15-Delta(12, 14)-deoxy-PGJ(2) (15dPGJ(2)) in cell culture supernatants was developed and validated. Pretreatment of the cell culture supernatants included only dilution and filtration, and the analysis time including all sample preparation steps was 60 min per sample. Peptides/proteins contained in the matrix were removed by the SCX column. LODs in the range of 8-44 pg/mL (25-120 pM) cell culture supernatant were obtained. Excellent linearity (R(2) > 0.99) and satisfactory recoveries and within- and between-day precisions were obtained. Human mesenchymal stem cells (hMSCs) were stimulated with tumor necrosis factor alpha (TNFalpha) or TNFalpha/IL-17, and PG production was analyzed using the developed method. The four PGs, 6kPGF(1a), PGF(1a), PGE(2), and PGE(1 )were detected both in nonstimulated and stimulated cells. The amount of PG produced by the cell increased when the cell was stimulated.     

Synthesis, characterization, and reactivity of [Li(N6,N9-Me2Ade(-H))]: a structurally characterized lithiated adenine

The reaction of N6,N9-dimethyladenine (N6,N9-Me2Ade, 1) with methyllithium in aprotic solvents such as tetrahydrofuran and pyridine resulted in the formation of the lithiated adenine [Li(N6,N9-Me2Ade-H)] (2) that was isolated as highly air and moisture sensitive tetrahydrofuran (2.(1/4)THF) and pyridine (2.py) adducts in excellent yields (>90%). The identities of 2.(1/4)THF and 2.py were confirmed by 1H and 13C NMR spectroscopy. In crystals of 2.(3/2)py, the dimethyladeninato ligand exhibited a chelating and bridging coordination mode (kappa2N6,N7:kappaN3) resulting in a 1-D polymeric chain-like structure in which the tetrahedral coordination sphere of the lithium atoms was completed by a pyridine molecule. Reactions of 2.(1/4)THF with electrophiles such as MeI, Me3SiCl, and Me3SnCl resulted in high yields (88-98%) of the formation of the adenine deriatives N6,N6,N9-Me3Ade-H (3), N6-(SiMe3)-N6,N9-Me2Ade(-H) (4), and N6-(SnMe3)-N6,N9-Me2Ade-H (5), respectively. Compounds 3-5 were characterized by 1H, 13C, 29Si (4), and 119Sn (5) NMR spectroscopy and MS investigations, and the stannylated derivative 5 also was characterized by single-crystal diffraction analysis exhibiting a mononuclear structure. The reaction of the stannylated adenine 5 with n-BuLi in n-hexane proceeded in the sense of a tin-lithium transmetalation reaction yielding the solvent-free lithium adeninate [Li(N6,N9-Me2Ade-H)] (2) in 90% yield.     

1,4-二锂四苯基-1,3-丁二烯与卤代烃反应的研究(Ⅱ)——与溴甲烷的反应

1,4-二锂四苯基-1,3-丁二烯与溴甲烷反应生成顺,顺-和顺,反-2,3,4,5-四苯基-2,4-己二烯。其分子结构和比例由MS、NMR及X射线单晶分析所确定。讨论了产物的生成途径。     

Asperflavipine A: A Cytochalasan Heterotetramer Uniquely Defined by a Highly Complex Tetradecacyclic Ring System from Aspergillus flavipes QCS12

Asperflavipines A ( 1 ) and B ( 2 ), two structurally complex merocytochalasans, were isolated from Aspergillus flavipes . Asperflavipine A ( 1 ), which contains two cytochalasan moieties and two epicoccine moieties, is the first cytochalasan heterotetramer to be discovered. It is uniquely defined by 5/6/11/5/6/5/6/5/6/5/5/11/6/5 fused tetradecacyclic rings with three continuous bridged ring systems. Asperflavipine B ( 2 ) is a cytochalasan heterotrimer containing a cytochalasan and two epicoccine moieties with a 5/6/11/5/5/6/5/6/5 nonacyclic ring system. The hypothetical biosynthesis of 1 and 2 is proposed to involve Diels–Alder and [3+2] cycloaddition reactions as key steps and reveals unparalleled plasticity in the biosynthesis of merocytochalasans. The existence of 1 adds a new dimension to the diversity of the cytochalasan family. Compound 1 showed moderate cytotoxicity and induced apoptosis in Jurkat, NB4, and HL60 cells through the activation of caspase‐3 and degradation of poly(ADP‐ribose) polymerase (PARP).     

Hexacyanometalate molecular chemistry: heptanuclear heterobimetallic complexes; control of the ground spin state

Following a bottom-up approach to nanomaterials, we present a rational synthetic route from hexacyanometalates [M(CN)(6)](3-) (M=Cr(III), Co(III)) cores to well-defined heptanuclear complexes. By changing the nature of the metallic cations and using a localised orbital model it is possible to control and to tune the ground state spin value. Thus, with M=Cr(III), d(3), S=3/2, three heptanuclear species were built and characterised by mass spectrometry in solution, by single-crystal X-ray diffraction and by powder magnetic susceptibility measurements, [Cr(III)(CNbondM'L(n))(6)](9+) (M'=Cu(II), Ni(II), Mn(II), L(n)=polydentate ligand), showing spin ground states S(G)=9/2 [Cu(II)], with ferromagnetic interactions J(Cr,Cu)=+45 cm(-1), S(G)=15/2 [Ni(II)] and J(Cr,Ni)=+17.3 cm(-1), S(G)=27/2 [Mn(II)], with an antiferromagnetic interaction J(Cr,Mn)=-9 cm(-1), (interaction Hamiltonian H=-J(Cr,M) [S(Cr)Sigma(i)S(M)(i)], i=1-6). With M=Co(III), d(6), S=0, the heptanuclear analogues [Co(III)(CN-M'L(n))(6)](9+) (M'=Cu(II), Ni(II), Mn(II)) were similarly synthesised and studied. They present a singlet ground state and allow us to evaluate the weak antiferromagnetic coupling constant between two next-nearest neighbours M'-Co-M'.     

一种含假芪型偶氮生色团两亲性嵌段共聚物的合成与表征

利用原子转移自由基聚合（ATRP）合成了一种新型的含假芪型偶氮生色团的两亲性嵌段共聚物P（HEMA-b-6CNAzo）。首先,采用ATRP引发剂引发三甲基硅保护的羟乙基甲基丙烯酸酯（HEMA—TMS）聚合,得到大分子引发剂P（HEMA—TMS）;接着进一步引发单体甲基丙烯酸6-（N_甲基苯胺基）己酯进行ATRP反应,得...     

Structural effects on interconversion of oxygen-substituted bisketenes and cyclobutenediones

Cyclobutenediones 5 disubstituted with HO (a), MeO (b), EtO (c), i-PrO (d), t-BuO (e), PhO (f), 4-MeOC6H4O (g), 4-O2NC6H4O (h), and 3,4-bridging OCH2CH2O (i) substituents upon laser flash photolysis gave the corresponding bisketenes 6a-i, as detected by their distinctive doublet IR absorptions between 2075 and 2106 and 2116 and 2140 cm-1. The reactivities in ring closure back to the cyclobutenediones were greatest for the group 6b-e, with the highest rate constant of 2.95 x 10(7) s-1 at 25 degrees C for 6e (RO = t-BuO) in isooctane, were less for 6a (RO = OH, k = 2.57 x 10(6) s-1 in CH3CN), while 6f-i were the least reactive, with the lowest rate constant of 3.8 x 10(4) s-1 in CH3CN for 6h (RO = 4-O2NC6H4O). The significantly reduced rate constants for 6f-i are attributed to diminution of the electron-donating ability of oxygen to the cyclobutenediones 5f-h by the ArO substituents compared to alkoxy groups and to angle strain in the bridged product cyclobutenedione 5i. The reactivities of the ArO-substituted bisketenes 6f-h in CH3CN varied by a factor of 50 and gave an excellent correlation of the observed rate constants log k with the sigma p constants of the aryl substituents. Computational studies at the B3LYP/6-31G(d) level of ring-closure barriers are consistent with the measured reactivities. Photolysis of squaric acid (5a) in solution provides a convenient preparation of deltic acid (7).     

Camptothecinoids from the seeds of Taiwanese Nothapodytes foetida

Two new alkaloids, 9-methoxy-18,19-dehydrocamptothecin (1) and 5- hydroxymappicine-20-O-beta-glucopyranoside (2a/2b as a racemic mixture), together with nine known compounds: camptothecin (3), 9-methoxy-camptothecin (4), 5-hydroxycamptothecin (5a/5b racemic mixture), 5-hydroxy-9-methoxycamptothecin (6a/6b racemic mixture), diosmetin (7), apigenin (8), apigenin-7-O-glucopyranoside (9), rosin (cinnamyl-O-beta-D-glucopyranoside) (10) and amarantholidoside IV (11) were isolated from the immature seeds of Nothapodytes foetida (Wight) Sleumer. The structures were elucidated by spectroscopic analyses. In the present research, compounds 1, 3, 4, 5a/5b and 6a/6b, also showed in vitro cytotoxicity against six cancer cell lines (HepG2, Hep3B, MDA-MB- 231, MCF-7, A549, and Ca9-22). Among them, compound 1 exhibited significant cytotoxicity against these cancer cell lines, with IC(50) of 0.24-6.57 microM. Furthermore, HPLC profiles were developed for qualitative and quantitative analysis of these active constituents in different parts of this plant, including mature and immature seeds, leaves, stems and roots. The results revealed that compounds 3 and 4 have the highest concentrations, which are found in the roots part of the plant.