Two new complex triterpenoid saponins from Gledistsia dolavayi Franch.

Two new triterpenoid saponins, gledistside A ( 1 ) and gledistside B ( 2 ), isolated from the fruits of Gledistsia dolavayi Franch., were characterized as the 3,28‐O‐bisdesmoside of echinocystic acid acylated with monoterpene carboxylic acids. On the basis of spectroscopic and chemical evidence, their structures were elucidated as 3‐O‐β‐D ‐xylopyranosyl‐(1→2)‐α‐L ‐arabinopyranosyl‐(1→6)‐β‐D ‐glucopyranosyl‐28‐O‐β‐D ‐xylopyranosyl‐(1→3)‐β‐D ‐xylopyranosyl‐(1→4)‐[β‐D ‐galactopyranosyl‐(1→2)]‐α‐L ‐rhamnopyranosyl‐(1→2)‐{6‐O‐[2,6‐dimethyl‐6(S)‐hydroxy‐2‐trans‐2,7‐octadienoyl]}‐β‐D ‐glucopyranosylechinocystic acid ( 1 ) and 3‐O‐β‐D ‐xylopyranosyl‐(1→2)‐α‐L ‐arabinopyranosyl‐(1→6)‐β‐D ‐glucopyranosyl‐28‐O‐β‐D ‐xylopyranosyl‐(1→3)‐β‐D ‐xylopyranosyl‐(1→4)‐[β‐D ‐galactopyranosyl‐(1→2)]‐α‐L ‐rhamnopyranosyl‐(1→2)‐{6‐O‐[2‐hydroxymethyl‐6‐methyl‐6(S)‐hydroxy‐2‐trans‐2,7‐octadienoyl]}‐β‐D ‐glucopyranosylechinocystic acid ( 2 ). The complete ¹H and ¹³C assignments of saponins 1 and 2 were achieved on the basis of 2D NMR spectra including HMQC‐TOCSY, TOCSY, ¹H–¹H COSY, HMBC, ROESY and HMQC spectra. Copyright © 2002 John Wiley & Sons, Ltd.     

四棱草中环八肽的二维核磁共振谱研究

以二维核磁共振谱（2D NMR）解析了从四棱草核磁共振谱（Schnabelia oligophyllaHand.Mazz.）中分离的环八肽--四棱草环肽（Schnabepeptide）的结构. 通过¹H-¹H COSY和¹H-¹HTOCSY归属了组成四棱草环肽的丝氨酸（L-Ser）、异亮氨酸（L-Ile）、甘氨酸（Gly）、色氨酸（D-Trp）、2个缬氨酸（L-Val）和2个脯氨酸（Pro）共8个氨基酸残基的质子耦合系统，¹³C NMR谱的归属则由HMQC和HMQC-TOCSY给出，由2D NOESY和HMBC对环肽各残基的连接方式进行了修正，鉴定的结果为Cyclo-(NH-Trp-Val-Gly-Val-Ser-Ile-Pro-Pro-CO).     

二蕊荷莲豆环肽B的NMR应用研究

植物环肽的¹H 和¹³C NMR图谱, 由于各种氨基酸自旋系统质子和碳的化学位移非常接近，谱峰高度重叠，结构解析比较困难. 文中以二蕊荷莲豆环肽B为例讨论了
现代2D NMR新技术，在植物环肽结构解析中的应用. HMQC-TOCSY图谱在氢谱方向和碳谱方向分别提供每一个氨基酸自旋系统内的氢和除季碳外碳的全相关信息，从而将每个氨基酸残基的NMR信号相互区分开来；结合¹H-¹H COSY 和 HMQC或HSQC图谱，就可以准确归属每个氨基酸的氢和碳的化学位移. 氨基酸残基之间的连接顺序可用HMBC、NOESY或ROESY图谱获得.     

Validation of the mPW1PW Quantum chemical calculations for the vibrational study of organic molecules – re‐assignment of the isopropylamine vibrational spectra

The validity of the mPW1PW91 density functional theory (DFT) method coupled to the all‐electron basis set 6‐31G* (mPW1PW/6‐31G*) for the study of amines, using isopropylamine (iPram) as a case study, was evaluated. Validation was performed by comparing the calculated values with the corresponding experimental results obtained and/or reported in the literature. Moreover, the accuracy of that theoretical level was compared with that of other widely used theoretical levels, namely HF/6‐31G*, B3LYP/6‐31G* and MP2/6‐31G*. The effect of basis set improvement within the mPW1PW protocol was evaluated considering the widely used 6‐311G** basis set. On the whole, the results clearly show that the mPW1PW/6‐31G* calculations are a suitable tool for the prediction of the structural and vibrational features of iPram. The validation of the theoretical methodology allowed a complete revision of the vibrational assignments previously reported in the literature, being the result of several proposed re‐assignments. Copyright © 2010 John Wiley & Sons, Ltd.     

Worst-Case Fault Detection Observer Design: Optimization Approach

This paper deals with the fault detection problem for linear systems with unknown inputs. The H _∞ norm and H ₋ index are employed to measure the robustness to unknown inputs and the sensitivity to faults, respectively. By using the pole assignment approach, the fault detection problem is transformed to an unconstrained optimization problem. With the aid of a gradient-based optimization approach, an explicit formula for designing the desirable observer gain is derived. Furthermore, the fault sensitivity over a finite frequency range can also be solved by the proposed method. The methodology proposed is verified through numerical simulation studies performed on the fault detection observer design of a vertical takeoff and landing aircraft. This work was supported in part by DSO National Laboratories under Grant DSOCL-01144, by Nanyang Technological University under Grant RGM 34/01, and by HKU CRCG 10204304. Part of this work was presented in 2004 American Control Conference [1].     

Identification of hot band transitions of CH4 near 3000 cm

Rovibrational transitions between vibrationally excited states of ¹²CH₄ in the 3.4 μm wavelength region are investigated by a pump-probe technique using an optical parametric oscillator as a pump and a tunable diode laser as a probe. Methane molecules are excited into selected levels of the 2ν₃ state of the tetradecad and numerous transitions between pentad and tetradecad, and between tetradecad and triacontad, have been observed in this spectral range. Positions and assignments of transitions involving a level of the 2ν₃ (F₂) substate are reported. Reliable energy values for 2ν₃ (F₂) levels up to J = 6 are obtained, and the energies and assignments of a number of 3ν₃ levels have been deduced allowing identification of IR lines in the 1.1 μm region.     

强∑~*空间是D空间

研究了强Σ~*空间和D空间的关系,证明了强Σ~*空间是D空间,改进了R.Z.Buzyakova等的结果.     

Structural and vibrational studies of molecular conductors using quantum mechanical methods: 1,3-Dithiole-2-thione, 1,3-dithiole-2-one, 1,3-dioxole-2-one and 1,3-dioxole-2-thione

Computations were carried out by employing the RHF and density functional theory (DFT) methods to investigate the geometries, atomic charges, harmonic vibrational frequencies for the 1,3-dithiole-2-thione (DTT), 1,3-dithiole-2-one (DTO), 1,3-dioxole-2-thione (DOT) and 1,3-dioxole-2-one (DOO) molecules and their radical cations. The geometrical parameters and atomic charges on various atomic sites of the DTT and DOT molecules and their radical cations suggest extended conjugation in these systems. Contrary to this, for the DOO⁺ and DTO⁺ ions there is no evidence in favour of such conjugation, however, the neutral molecules exhibit some conjugation. Harmonic forced field and vibrational mode calculations provided convincing theoretical evidence for the reassignment of some fundamental vibrational modes for all the four molecules. In going from the neutral species to the charged ions for all the four cases the CC stretching frequency is found to decrease drastically. The CS stretching frequency reduces drastically for the DTT and DOT molecules as compared to their radical cations whereas the CO stretching frequency is found to increase in going from the neutral molecule to its radical cation for the DOO and DTO molecules. The ring stretching mode with a₁ symmetry and CC and CO/S stretching modes in these molecules appear to help in conversion of neutral molecule into respective radical cation and neighbouring radical cation into respective neutral molecule. Thus, there appears the feasibility of stretching vibrational mode coupling with electron transfer.     

新药替尼泊苷的碳氢NMR信号全归属

替尼泊苷是从北美鬼臼或西藏鬼臼提取到的鬼臼树脂,经化学成分分离得到鬼臼毒素通过半合成方法获得的衍生物,是一种周期特异性细胞毒药物.作为一种抗肿瘤药物,替尼泊苷已逐渐成为治疗颅内恶性肿瘤的主要化疗药物.本文应用1D NMR和2D NMR实验技术（COSY,NOESY,TOCOSY,gHSQC,gHMBC）研究了其结构,并对其¹H NMR、¹³C NMR谱信号进行了全归属.     

Complete assignments of 1H and 13C NMR data for ten phenylpiperazine derivatives

Ten phenylpiperazine derivatives were designed and synthesized. The first complete assignments of (1)H and (13)C NMR chemical shifts for these phenylpiperazine derivatives were achieved by means of 1D and 2D NMR techniques, including (1)H-(1)H COSY, HSQC and HMBC spectra.