Further Daphniphyllum Alkaloids from the Leaves of Daphniphyllum macropodum Miq.

Five new polycyclic Daphniphyllum alkaloids, macropodumines F ( 1 ) and G ( 2 ), 17‐oxoyuzurimine ( 3 ), and macropodumines H ( 4 ) and I ( 5 ), were isolated from the leaves of D. macropodum Miq ., collected in Sichuan Province, China. The structures and relative configurations of the new compounds – as well as of four known, related alkaloids – were elucidated on the basis of in‐depth spectroscopic and mass‐spectrometric analyses, by chemical derivatization, and by comparison of spectroscopic data with those of known compounds.     

Proton transfer dynamics of the reaction H3O(+)(NH3,H2O)NH4+ studied using the crossed molecular beam technique

The proton transfer reaction of H3O+ and NH3 was studied using the crossed molecular beam technique at relative energies of 0.41, 0.81, and 1.27 eV. At all three energies, the center-of-mass flux distribution of the product ion NH4+ exhibits sharply asymmetry, and the maximum is close to the velocity and direction of the precursor ammonia beam. The reaction transforms almost all of the 1.69 eV exothermicity into internal excitation of the products at all three collision energies. At the lowest collision energy of 0.41 eV, nearly 77% of the total energy appears in NH4+ internal excitation. However, almost 100% of the incremental translational energy in the two higher-energy experiments appears in the product translational energy. Such an observation provides a classic example of the "induced repulsive energy release" mechanism that is expected to be operative on the highly skewed potential energy surfaces characteristic of the heavy+light-heavy mass combination. These results indicate that the proton transfer proceeds through a direct reaction mechanism; a Rice-Ramsperger-Kassel-Marcus theory calculation shows that the lifetime of the intermediate complex [NH3-H-H2O]+ is about 100 fs. Proton transfer occurs early on the reaction coordinate, when the incipient N-H bond is extended, and results in highly vibrationally excited NH4+ products, with excitation primarily in N-H stretching modes.     

“NMR invisible” aluminum species in dealuminated mordenite zeolite: a1H/27 AI TRAPDOR NMR study

Various kinds of aluminum species in dealuminated mordenite were investigated in detail, and the quadrupole coupling constants (QCCs) for aluminum atoms associated with these species were obtained by means of the newly introduced¹H/²⁷ AI TRAPWR method as well as²⁷Al magic angle spinning (MAS) nuclear magnetic resonance (NMR). QCC values of 11.3, 15.3, 13.3 and (14.0± 0.6) MHz were determined from the TRAPDOR profiles for Lewis acid sites, Bronsted acid sites (SiOHAl) and two kinds of non-framework aluminum species Al(OH) _n , respectively. The source of the “invisible Al” is discussed on the basis of the NMR experimental results.     

Isolation and purification of the bioactive carotenoid zeaxanthin from the microalga Microcystis aeruginosa by high-speed counter-current chromatography

High-speed counter-current chromatography was successfully applied for the first time to the isolation and purification of the bioactive carotenoid zeaxanthin from the cyanobacterium Microcystis aeruginosa. The crude zeaxanthin was obtained by extraction with organic solvents after the microalgal sample had been saponified. Preparative high-speed counter-current chromatography with a two-phase solvent system composed of n-hexane-ethyl acetate-ethanol-water (8:2:7:3, v/v/v/v) was successfully performed yielding zeaxanthin at 96.2% purity from 150 mg of the crude extract in a one-step separation. The recovery of zeaxanthin was 91.4%. This was also the first report that zeaxanthin was successfully separated and purified from microalgae.     

纳米管束的合成及结构

用电弧法制备出纳米管及纳米管束，并用高分辨电镜观察其结构．观察到的纳米管管子中空，管壁平行，间距0．34nm，端部封闭；还观察到单层纳米管，洋葱球以及内包晶核的洋葱球结构，纳米管束微结构为纳米管．用扫描电镜观察，为明显的针状晶须，定向排列，晶须互相平行，平行于电场方向生长，晶须直径0．2～0．6mm，长度3～8mm．生成纳米管束的原因可能是由于掺杂碳棒中的杂质提供了晶须生长的晶核．     

New Nitrogenous Bisabolene‐Type Sesquiterpenes from a Hainan Sponge Axinyssa aff. variabilis

Two new uncommon nitrogenous sesquiterpenes, 11‐ethoxy‐3‐formamidotheonellin ( 1 ) and 7‐ethoxy‐3‐formamidobisabolane‐8,10‐diene ( 2 ), together with two known related sesquiterpenes, 3‐formamidotheonellin (=theonellin formamide; 3 ) and theonellin isothiocyanate ( 4 ), were isolated from the Hainan sponge Axinyssa aff. variabilis. Their structures were determined on the basis of extensive spectroscopic analysis and by comparison of their NMR data with those of known compounds.     

Streamlined construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation in solution and on DNA

A highly efficient and versatile method for construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation of alkyl and aryl thiols with aryl iodides under mild conditions is developed. The method exhibits a broad substrate scope for thiols, aryl iodides and amino acid units. Peptide macrocycles of a wide range of size and composition can be readily assembled in high yield from various easily accessible building blocks. This method has been successfully employed to prepare an 8-million-membered tetrameric cyclic peptide DNA-encoded library (DEL). Preliminary screening of the DEL library against protein p300 identified compounds with single digit micromolar inhibition activity.

A highly efficient and versatile method for construction of peptide macrocycles via palladium-catalyzed intramolecular S-arylation of alkyl and aryl thiols with aryl iodides under mild conditions is developed.     

Synthesis of chiral γ-lactones via a RuPHOX-Ru catalyzed asymmetric hydrogenation of aroylacrylic acids

An asymmetric hydrogenation of aroylacrylic acids catalyzed by RuPHOX-Ru catalyst has been developed, affording the corresponding chiral γ-lactones in high yields and with up to 93% ee. The methodology has the advantage of utilizing easily accessible substrates and has therefore expand the scope of the resulting chiral γ-lactones. Furthermore, high catalytic efficiency was achieved in that the reduction of both the CC and CO double bonds was achieved in one step. The current work provides an alternative and convenient pathway for the synthesis of a wide range of chiral γ-lactones.     

二氧化碳—环氧丙烷—甲苯二异氰酸酯的三元共聚

二氧化碳和环氧丙烷(PO)在阴离子配位催化剂,如二乙基锌和等摩尔的水作用下,可接式(1)发生共聚。但产物聚丙撑碳酸酯(PPC)的热稳定性较差。改进途径之一是在反应中引入甲苯二异氰酸酯(TDI)进行三元共聚。本文报导在双金属阴离子配位催化剂PBM存在下合成一种热稳定性优于PPC的聚碳酸酯聚氨酯(PCPU)的研究结果(式2)。     

有机锆交联剂的制备及其性能

随着油田深部调剖应用的不断推广，以及环保要求的提高，适用于深部调剖调驱体系的低污染有机锆交联剂逐渐受到关注。以ZrOCl₂·8H₂O、乳酸、乙二胺、硫脲为原料，制备了有机锆交联剂和HPAM-锆交联凝胶，其结构和性能经SEM和岩心驱替装置表征。并利用正交实验法优化了制备条件。结果表明：制备有机锆交联剂的最佳条件为：氧氯化锆、乳酸、乙二胺及硫脲的质量比为7.8/1/6.7/5，反应温度为70 ℃，反应时间为3 h。交联温度为60 ℃，HPAM浓度为2 g·L^-1、聚锆比为30/1时，聚合物凝胶成胶强度达到24968 mPa·s，成胶时间约8 h，凝胶体系可维持90 d不破胶。在级差为3.9的双管驱替岩心实验中，两管的岩心分流率均接近50%，剖面改善率达到66.77%。