STRUCTURES OF THE BERGAMOTTIN PHOTOPRODUCTS

The extensive use of bergamot oil in perfumery and cosmetics led us to study the photoreactivity of 5-geranoxypsoralen (bergamottin), the major chromophore in this oil. Structure determination of the bergamottin photoproducts was achieved using extensive NMR techniques including two-dimensional NMR: ¹H-¹³C correlation by long-range coupling, ¹H-¹H correlation spectroscopy (COSY) and ¹H-¹H COSY phase sensitive (COSYPH). Bergaptol is formed according to the well-known fragmentation of allyl-aryl ethers. The other photoproducts arise from an intramolecular [2 + 2] photocycloaddition and appeared as an equimolecular mixture of diastereomeric cyclobutyl derivatives. The relative configurations were determined by nuclear Overhauser effect analysis. These structures were further corroborated by X-ray crystal analysis. The facile formation of an intramolecular cyclobutyl derivative in bergamottin might prevent the intermolecular cyclobutane adduct formation with pyrimidine DNA bases responsible, in part, for phototoxicity of psoralens.     

脯氨酸类N-酰胺衍生物的核磁共振研究

脯氨酸类衍生物结构独特,鲜有报道利用核磁共振（nuclear magnetic resonance,NMR）技术对氨基酸的手性进行鉴别.利用多种NMR技术:1H NMR、1H-1H同核位移相关谱（1H-1H COSY）、1H-1H质子全相关谱（1H-1H TOCSY）、1H-1H核Overhauser效应谱（1H-1H NOESY）、13C NMR、无畸变的极化转移增强法（DEPT135°）、1H-13C检出1H的异核单量子相干（1H-13C HSQC）和1H-13C检出1H的异核多键相关（1H-13C HMBC）,对脯氨酸类N-酰胺衍生物两种构象异构体的1H和13C NMR进行了全归属,确定了室温下在二甲基亚砜（DMSO）中L型和D型的顺反异构体以相同的比例同时存在.     

盐酸莫西沙星的结构分析研究

报道了盐酸莫西沙星的元素分析、红外光谱(IR) 、紫外光谱(UV) 、质谱(MS) 、氢-氢相关谱(1H-1HCOSY) 、碳谱(DEPT-45、DEPT-90、DEPT-135) 、多键碳氢相关谱(HMBC)等波谱数据,并对特征数据进行了化合物的结构解析。对所有的1H-NMR、13C-NMR谱的信号进行了归属。     

Dynamic Equilibrium between a Supramolecular Capsule and Bowl Generated by Inter‐ and Intramolecular Metal Clipping

The metal‐induced self‐assembly of a resorcin[4]arene derivative 1 that has four pyridine units as pendent groups and two equivalents of [M(dppp)(OTf)₂] (M=Pd, Pt) results in a dynamic equilibrium between an interclipped supramolecular capsule 3 and an intraclipped bowl 4 in nitromethane, although the interclipped capsule 3 is formed as a sole adduct in chloroform/methanol and the intraclipped bowl 4 is formed exclusively in an aqueous phase. This demonstrates how metal‐induced self‐assembly can be tuned by subtle changes in the solvent system. The coexistence of the two structures in nitromethane was characterized by NMR spectroscopy and coldspray ionization mass spectrometry (CSI‐MS). The crystal structure of the interclipped capsule 3 b , which is composed of two units of ligand 1 and four Pt^II ions, reveals the capsule cavity to have nanoscale dimensions of 15×20 Å. NMR spectra show that the dynamic equilibrium between 3 and 4 is dependent on concentration and temperature. Temperature‐dependent ¹H NMR spectroscopy was carried out from 273 to 343 K to verify the thermodynamic parameters that control the dynamic equilibrium process; the conversion from the interclipped supramolecular capsule 3 a to the intraclipped bowl 4 a is entropically favored and enthalpically disfavored. The rotational barrier of the restricted rotation of pyridine units in the intraclipped bowl 4 was determined by line‐shape analysis.     

Hydrogen-bonded network and enforced supramolecular cavities in molecular crystals: An orthogonal aromatic-triad strategy. Guest binding,molecular recognition,and molecular alignment properties of a bisresorcinol derivative of anthracene in the crystalline state

Abstract

Crystallization of an orthogonal resorcinol-anthracene-resorcinol compound 1a (host) from an ester solvent such as alkyl benzoate (guest) affords a 1:2 host-guest adduct 1a·2(ester). An essential aspect of the crystal structures of ethyl, propyl, and isobutyl benzoate adducts (space group, P2₁/n) and also that of methyl benzoate adduct (C2/c) is an extensive hydrogen-bonded network of host 1a, leading to a molecular sheet composed of hydrogen-bonded polyresorcinol chains and anthracene columns. This network generates well-defined, cyclophane-like supramolecular cavities, which incorporate two alkyl benzoate molecules in a highly selective manner via a combination of essential host-guest hydrogen-bonding and what may be called the cavity-packing effect. The selectivity factor between methyl benzoate (the lowest-affinity guest) and isobutyl benzoate (the highest-affinity guest) is 1:70 under competitive conditions. The actual geometry of the cavity is somehow dependent on and hence induced-fit adjustable to the guest structures by manipulating the intramolecular (anthracene-resorcinol dihedral angle) and intermolecular conformation (tilt angle between two hydrogen-bonded resorcinol rings) of compound 1a as well as the sheet-to-sheet distance. The adducts 1a·2(guest) can also be obtained by solid-state guest-exchange or guest-binding, respectively, using a preformed adduct or guest-free apohost dipped in an appropriate guest solvent. The methyl benzoate adducts obtained in these ways exhibit the same X-ray powder diffraction pattern as the genuine single-crystal obtained by direct crystallization of host 1a from methyl benzoate. Thus, even internal supramolecular cavities maintained by the hydrogen-bonded network are readily accessible to molecules in bulk solution. In addition, they undergo an induced-fit adjustment to a guest molecule newly added by the guest-exchange or the guest-binding process, during which the crystallinity is maintained. The potential use of symmetrical and divergent multiple hydrogen-bonding sites with an orthogonal aromatic spacer (orthogonal aromatic-triad strategy) is discussed in terms of a tool to construct a new class of porous organic crystals that show novel molecular recognition, crystalline-state guest-binding, and crystalline-phase molecular alignment properties.     

5-amino-2-methylpyridinium hydrogen fumarate: An XRD and NMR crystallography analysis

Single-crystal X-ray diffraction structures of the 5-amino-2-methylpyridinium hydrogen fumarate salt have been solved at 150 and 300 K (CCDC 1952142 and 1952143). A base–acid–base–acid ring is formed through pyridinium-carboxylate and amine-carboxylate hydrogen bonds that hold together chains formed from hydrogen-bonded hydrogen fumarate ions. ¹H and ¹³C chemical shifts as well as ¹⁴N shifts that additionally depend on the quadrupolar interaction are determined by experimental magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) and gauge-including projector-augmented wave (GIPAW) calculation. Two-dimensional homonuclear ¹H-¹H double-quantum (DQ) MAS and heteronuclear ¹H-¹³C and ¹⁴N-¹H spectra are presented. Only small differences of up to 0.1 and 0.6 ppm for ¹H and ¹³C are observed between GIPAW calculations starting with the two structures solved at 150 and 300 K (after geometry optimisation of atomic positions, but not unit cell parameters). A comparison of GIPAW-calculated ¹H chemical shifts for isolated molecules and the full crystal structures is indicative of hydrogen bonding strength.     

Synthesis and 1H, 13C and 15N NMR characterisation of substituted Pyrazolo[4,3-c]quinolines and related compounds

A wide range of novel and known alkyl substituted pyrazolo[4,3-c]quinolines and related compounds were synthesized. Some of these compounds can undergo tautomerism and differences have been noted in the structural assignments already published. For each of these compounds, a complete assignment was made using ¹H, ¹³C and ¹⁵N one- and two-dimensional NMR measurements, including NOESY, COSY, ¹H-¹³C HSQC and ¹H-¹³C HMBC. ¹H-¹⁵N HMBC NMR has proved crucial in determining the relevant tautomeric and protonated state of the compounds.     

Purealin,a novel enzyme activator from the Okinawan marine sponge Psammaplysilla purea

Purealin , a novel secondary metabolite, which modurates enzymic reactions of ATPases, has been isolated from the okinawan marine sponge $\text{Psammaplysilla}$$\text{purea}$ and the structure has been determined by the ¹H-¹H homonuclear and ¹H-¹³C heteronuclear NMR chemical shift correlations and CD spectra.     

Simulation of 2D H homo- and H-C heteronuclear NMR spectra of organic molecules by DFT calculations of spin-spin coupling constants and H and C-chemical shifts

Simulation of 2D ¹H homo- and ¹H-¹³C heteronuclear NMR spectra of organic molecules are here suggested as a tool in the structure elucidation of organic compounds. DFT calculations of ¹H and ¹³C chemical shifts are performed on a sample compound, the ethyl ester of the exo-2-norbornanecarbamic acid, with the mPW1PW91 method using the 6-31G(d) basis set, following a full optimization of the geometry. Homo and heteronuclear spin-spin coupling constants are also calculated, providing full prediction of the common 2D ¹H-¹H COSY, 2D ¹H-¹³C HSQC, and 2D ¹H-¹³C HMBC.     

Synthesis and characterization of a new pillar[5]arene-based [1]rotaxane

In this study, we reported the synthesis of three kinds of mono-functional pillar[5]arene derivatives PRI, PRII and R and their structures were studied by 1D and 2D NMR spectra and mass spectra. The 2D NMR spectra including ¹H-¹³C HSQC, ¹H-¹H COSY and NOESY spectra indicated that PRI and PRII are both stable self-included pseudo[1]rotaxanes in CDCl₃. These original structures are promising compounds for the design of pillar[5]-based [1]rotaxane. And the results showed that R could exist stable in CDCl₃ and DMSO because of the coordination of N-H?O hydrogen bonding interaction and C-H?π interaction.     

Spectra and structure of binary azeotropes VI-benzene-methanol

Benzene and methanol make a minimum boiling point homogeneous binary azeotrope with the mole ratio 2:3. Some characteristic vibrational modes, as well as ¹H NMR signals change due to the azeotrope formation. The extend of interaction of these molecules causes significant changes on some vibrational modes involved, and ¹H NMR signals show some changes on their position. No IR, Raman, and NMR spectra have been reported for this constant boiling mixture, also there has not been any attempt to investigate the unit-structure of this azeotrope. In this work the FTIR, FT-Raman, and ¹H NMR spectra of pure benzene, pure methanol, and corresponding azeotrope were recorded, mutual influences resulting from azeotrope formation have been analyzed, and spectral changes has been discussed. The unit-structure of cluster has been deduced based on mole ratio, boiling point depression of constituents, and comparison among the spectra obtained by FTIR, FT-Raman, and ¹H NMR techniques.     

Triterpene glycosides ofAstragalus and their genins. XLVII. Structures of cycloalpigenin A and cycloalpioside A

The structures of two new cycloartane triterpenoids, cycloalpigenin A and cycloalpioside A, isolated from Astragalus alopecurus Pall. (Leguminosae) have been established on the basis of chemical transformations together with¹H,¹³C, and 2D¹H-¹H and¹H-¹³C chemical shift correlation NMR spectroscopy and IR, mass, and CD spectra. Cycloalpigenin A is 3β,16β,25-trihydroxy-20R,24S-epoxycycloartan-12-one, and cycloalpioside A is cycloalpigenin A 3-O-β-D-xylopyranoside.     

Heteroligand bipyridyl-pyridylbenzimidazole Ru(II) complexes. Synthesis,structural characterization,and investigation of electronic structure

Ruthenium(II) complexes with pyridylbenzimidazole derivatives were synthesized and investigated by NMR (¹H and ¹H-¹H COSY), mass, and electronic spectroscopy. Proceeding from quantum-chemical calculations by the density functionsl methods the analysis was performed of electronic and geometric structure of free ligands and Ru(II)complexes, and the electron absorption spectra of complexes under study were interpreted. Compared to [Ru(bpy)₃]²⁺ (bpy = 2,2′-bipyridyl) the charge transfer band in the visible range of the electronic spectra of the complexes in question suffered a red shift by ～10 nm, and its intensity in the absorption maximum is several times smaller. The introduction of acceptor substituents into the benzene ring of the pyridylbenzimidazole ligand did not affect significantly the spectral properties of the complexes.     

Carbon-13 and proton magnetic resonance spectra of 2,4-disubstituted 3,3-diphenyltetrahydrofurans derived from isomethadone and isomethadol

Proton and carbon-13 nmr spectra for cis- and trans-2-ethyl-3,3-diphenyl-4-methyltetrahydrofurans and 2-ethylidene-3,3-diphenyl-4-methyltetrahydrofuran, derived from the pyrolysis of the quaternary ammonium salts of the diastereomeric isomethadols and isomethadone, respectively, are reported. ¹H and ¹³C chemical shifts and ¹H-¹H coupling constants have been assigned in each case. The isomeric teterahydrofurans have been analyzed in terms of a half-chair conformation, and an envelope conformation for the ethylidene derivative.     

Two-dimensional Pure Isotropic Proton Solid State NMR

One key bottleneck of solid-state NMR spectroscopy is that ¹H NMR spectra of organic solids are often very broad due to the presence of a strong network of dipolar couplings. We have recently suggested a new approach to tackle this problem. More specifically, we parametrically mapped errors leading to residual dipolar broadening into a second dimension and removed them in a correlation experiment. In this way pure isotropic proton (PIP) spectra were obtained that contain only isotropic shifts and provide the highest ¹H NMR resolution available today in rigid solids. Here, using a deep-learning method, we extend the PIP approach to a second dimension, and for samples of L-tyrosine hydrochloride and ampicillin we obtain high resolution ¹H-¹H double-quantum/single-quantum dipolar correlation and spin-diffusion spectra with significantly higher resolution than the corresponding spectra at 100 kHz MAS, allowing the identification of previously overlapped isotropic correlation peaks.     

The Interaction of Benzyl Alcohol with Trimethoxyboroxine : Amine Adducts of Triarylboroxines as Model Compounds

The interaction of benzyl alcohol with trimethoxyboroxine has been investigated by hydrogen-1 and carbon-13 NMR and IR spectroscopy. These techniques indicate formation of a weak Lewis acid/base adduct, additionally stabilized by a hydrogen-bonding interaction, which undergoes rapid ligand exchange at room temperature. The system has been modelled by the synthesis and characterization of a series of amine-triarylboroxine adducts. These adducts rapidly undergo ligand dissociation-recombination in solution with ΔG⁺ of ca. 40-50 kJ/mol.     

Dipolar magnetic field effects in NMR spectra of liquids

Dipolar magnetic field effects have been detected in the NMR spectra of coronene and methylpyropheophorbide in liquid solution. These effects arise from the partial molecular alignment induced by the magnetic field. Both ¹H-¹H and ¹³C-¹H couplings have been detected. For both compounds the anisotropy in the diamagnetic susceptibility is calculated.     

Characterization of H2-Splitting Products of Frustrated Lewis Pairs: Benefit of Fast Magic-Angle Spinning

Proton spectroscopy in solid-state NMR on catalytic materials offers new opportunities in structural characterization, in particular of reaction products of catalytic reactions such as hydrogenation reactions. Unfortunately, the ¹H NMR line widths in magic-angle spinning solid-state spectra are often broadened by an incomplete averaging of ¹H-¹H dipolar couplings. We herein discuss two model compounds, namely the H₂-splitting products of two phosphane-borane Frustrated Lewis Pairs (FLPs), to study potentials and limitations of proton solid-state NMR experiments employing magic-angle spinning frequencies larger than 100 kHz at a static magnetic field strength of 20.0 T. The ¹H lines are homogeneously broadened as illustrated by spin-echo decay experiments. We study two structurally similar materials which however show significant differences in ¹H line widths which we explain by differences in their ¹H-¹H dipolar networks. We discuss the benefit of fast MAS experiments up to 110 kHz to detect the resonances of the H⁺/H⁻ pair in the hydrogenation products of FLPs.     

Interpretation dü spectre RMN-3H du PK-11195 (3H)

(1D-³H NMR) of PK 11195 ³H gives a complex spectrum. Homonuclear 2D-³H NMR (COSY and J. Resolved) gives useful information such as tritium chemical shifts, ³H-³H and ³H-¹H coupling constant, percentage of isotopomers and specific activity.     

Coordination behaviour of benzothiazolines towards stannous ion

Equimolar reactions of tin(II) methoxide with benzothiazolines result in the isolation of a new series of tin(II) complexes, which further undergo 1:1 adduct formation with pyridine. The electronic, IR and ¹H NMR spectral studies indicate coordination of tin to the oxygen, azomethine nitrogen and sulphur of the ligand moiety.