Session PH. There are 25 abstracts in this session.

Session: Small Molecules, poster number: 243
Complete Eradication of Axial Peaks and Preventing the Evolution of Unwanted Couplings in Gradient Encoded Selective Refocusing Experiments
Sandeep Mishra; Suryaprakash Nagarajarao
Indian Institute of Science, Bangalore, India
The available many two-dimensional selective refocusing (SERF) based experiments for the extraction of scalar couplings suffer from the evolution of magnetization from uncoupled protons, which appears as intense uninformative axial peaks. The novel experimental techniques developed, viz., the Clean-G-SERF completely eradicates the axial peaks and suppresses the evolution of unwanted couplings while retaining only the couplings to the selectively excited proton thereby permitting the accurate determination of indirect spin-spin couplings even from a complex proton NMR spectrum in an orchestrated manner. Another designed PS-Clean-G-SERF technique completely eliminates the axial peaks and undesired couplings in addition to providing ultra-high resolution by the incorporation of real time broad band homonuclear decoupling.

Session: Small Molecules, poster number: 244
Development of a Novel Pentafluorobenzene Derived Isothiocyanate For Use as a CDA
Emily Crull; Matthew Donahue
Univ of Southern Mississippi, Hattiesburg, MS
A chiral derivatizing agent has been developed to differentiate between enantiomers through the formation of a covalent bond thereby forming diastereomers. We have developed a pentafluorobenzene CDA that has no aromatic protons thereby allowing for simpler proton NMR interpretation. A novel chiral, non-racemic C6F5 benzylisothiocyanate has been synthesized over four-steps from pentafluorobenzaldehyde. The reaction of this isothiocyanate with chiral amines results in the production of diastereomeric thioureas. The electron withdrawing properties of the pentafluorophenyl ring allows for the two enantiomers of each amine to be differentiated by 1H and 19F NMR. Comparison of the observed chemical shifts with those calculated at the HF 3-21G level has served as the basis for a predictive model for determining enantiomeric excess by NMR.

Session: Small Molecules, poster number: 245
Polybiphenylmethylglutamate as enantiodifferentiating alignment medium for NMR-spectroscopy with temperature tunable properties
Sharon Jeziorowski
TU Darmstadt, Darmstadt, Germany
The use of anisotropic NMR parameters – especially residual dipolar couplings (RDCs) – offers access to additional structural information. The alignment media required are continuously being developed for a higher diversity of analyte and solvent compatibility as well as a better understanding of the orientational process itself. Thus, we decided to introduce a mesogenic biphenyl group into the sidechain of a homopolypeptide. As mesogenes themselves can form LLC-Phases, we were wondering which effect this has on the orienting features. Herein we report about the performance of poly(-p-biphenylmethyl-glutamate) (PBPMG) as a versatile new enantiodifferentiating alignment medium with temperature tunable properties. The outstanding orientational properties along with excellent spectral quality even allow enantiodifferentiation of mixtures of enantiomers within one sample.

Session: Small Molecules, poster number: 246
Probing Amino Acid Adsorption on Polystyrene Nanoparticle Surfaces Using STD-NMR
Yunzhi Zhang; Leah Casabianca
Clemson University, Clemson, SC
Amino acids, as the building blocks of peptides and proteins, significantly govern biomolecule properties. A better understanding of amino acids interacting with nanoparticles will give us more knowledge about the interactions between nanoparticles and peptides or proteins. Saturation Transfer Difference (STD)-NMR is a useful tool for detecting noncovalent binding between proteins and small drugs. In the present work we examine the adsorption of amino acids on the surface of PS nanoparticles using 1D proton NMR and STD-NMR. We first compare the binding strength of various amino acids. Second we elucidate molecular-level details about the structure of amino acids when interacting with PS nanoparticles. This work will be important in explaining interactions between nanoparticles and peptides or proteins.

Session: Small Molecules, poster number: 247
NOAH: NMR Supersequences for Small Molecule Analysis and Structure Elucidation
Eriks Kupce1; Tim D. W. Claridge2
1Bruker UK Ltd, Coventry, United Kingdom; 2Department of Chemistry, University of Oxford, Oxford, United Kingdom

A new concept of nested NMR experiments combining several conventional NMR pulse sequences into one supersequence is introduced. The core 2D NMR techniques routinely employed in small molecule NMR spectroscopy, such as HSQC, HMQC, HMBC, COSY, NOESY, TOCSY, and similar, are recorded in a single measurement employing only a single recovery (relaxation) delay, d1. In this way the data collection time is dramatically reduced and sample throughput increased for basic NMR applications, such as structure elucidation and verification in synthetic, medicinal, and natural product chemistry. While not all of the proposed 285 NOAH supersequences are equally efficient and/or practical, the existence of a large number of possible combinations highlights the need for a systematic classification of this technique.


Session: Small Molecules, poster number: 248
Magnetic Resonance Spectroscopy and Imaging with Diamond Nitrogen Vacancy Centers
Nazanin Mosavian1; Ilja Fescenko1; Pauli Kehayias2; Janis Smits1; Abdelghani Laraoui1; Lykourgos Bougas3; Andrey Jarmola3; Victor Acosta1
1UNM, CHTM, Physics and Astronomy Dept., Albuquerque, NM; 2Harvard University, Physics Department, Cambridge, MA; 3ODMR Technologies Inc., El Cerrito, CA
We perform NMR spectroscopy of picoliter solutions using nitrogen vacancy centers in a microfluidic diamond chip. Analyte is prepolarized in a larger magnetic field and then adiabatically flowed to a microfluidic diamond NMR detector at low field. Separating the polarization and detection in this way theoretically provides spectral resolutions (<1 Hz), capable of resolving proton chemical shifts and J-coupling splittings, with a sensitivity (300 pT in 1s integration) sufficient to detect ~1 molar proton concentrations. We also used diamond magnetic microscopy to image the paramagnetic properties of synthetic and human-derived malarial hemozoin biocrystals. The stray magnetic field produced by individual malarial hemozoin nanoparticles was imaged as a function of field, confirming hemozoin's paramagnetic nature.

Session: Small Molecules, poster number: 249
Application of NMR screening methods with 19F detection to fluorinated compounds bound to proteins
Kazuo Furihata1; Mitsuru Tashiro2
1University of Tokyo, Tokyo, Japan; 2Meisei University, Hino, Japan
The combinational use of one-dimensional (1D) NMR-based screening techniques with 1H and 19F detections were applied to a human serum albumin–diflunisal complex. Since most NMR screening methods observe 1H spectra, the overlapped 1H signals were unavailable in the binding epitope mapping. However, the NMR experiments with 19F detection can be used as an effective complementary method. For the purpose of identifying the 1H and 19F binding epitopes of diflunisal, this posterr carries out a combinatorial analysis using 1H{1H} and 19F{1H} saturation transfer difference experiments. The differences of the 1H-inversion recovery rates with and without target irradiation are also analyzed for a comprehensive interpretation of binding epitope mapping.

Session: Small Molecules, poster number: 251
Detection of Polymorphs and Co-Crystals by Means of Solid-State NMR
Jaroslav Havlicek1; Gerhard Althoff- Ospelt2
1Zentiva k.s., Prague 10, Czech Republic; 2Bruker BioSpin GmbH, Rheinstetten, Germany
Solid-state NMR spectroscopy is one of the few techniques that allow unequivocal identification of polymorphs as well as the detection of polymorphic (crystalline) purity. It is suited for the detection and characterization of co-crystals, too.

Complementing 13C solid-state NMR 19F offers the advantage of selectivity and sensitivity: 19F usually is present in the active pharmaceutical ingredient (API), only, its 100% natural abundance allows the detection of low API concentrations, and its chemical shift strongly depends on the local environment. Discrimination of physical mixtures, salts, and co-crystals may be studied by 1H or 19F relaxation time measurements 15N solid state NMR is rather sensitive to the nitrogen protonation state and, therefore, can be used to characterize salt formation and hydrogen bonding.

Session: Small Molecules, poster number: 252
A selective-gradient-encoding method for single-scan high-resolution 2D J-Resolved spectra
Yuqing Huang; Haolin Zhan; Zhong Chen
Xiamen University, Xiamen, China
As an important technique of nuclear magnetic resonance, 2D J-resolved spectroscopy has been widely applied in structural and conformational analyses in chemistry and biology. However, applications of conventional 2D J-resolved spectroscopy are restrained by the necessity of the long experimental duration, unavailability of accurate quantitative information, and strict requirement on magnetic field homogeneity. In this abstract, a selective gradient encoding (SGEN) method is proposed for recording the 2D J-resolved spectrum in a single scan. The selective excitation in unison with gradient naturally delivers high-resolution spectrum because a certain resonance signal merely originates from a fraction of the sample length, thus holding robustness against field inhomogeneity along the encoding direction.

Session: Small Molecules, poster number: 253
COSY-J-resolved-2D and BASHD-COSY-J-resolved-2D: New Methods for Measuring
Proton-Proton Spin Coupling Constants of Multiplet Signals

Kazuo Furihata1; Mitsuru Tashiro2
1University of Tokyo, Tokyo, Japan; 2Meisei University, Hino, Japan
Natural products such as polyketides very often possess several spin systems consisting of a methine group directly linked to a methyl group (e.g. -CH-CH(CH3)-CH-). In such a spin system, the methine proton splits into a broadened multiplet by coupling with several vicinal protons, rendering analysis difficult of JH-H cross peaks of the aforesaid methine proton in DQF-COSY or E-COSY.
In order to overcome this problem, we have developed new techniques, called COSY-J-resolved-2D and BASHD-COSY-J-resolved-2D. In the COSY-J-resolved-2D method, JH-H is measured in observation of the COSY cross peaks in the J-resolved 2D spectrum. Each cross peaks tilted for 45 degrees, such as J-resolved 2D methods, generating higher resolution cross peaks than those of the J-resolved-COSY method.

Session: Small Molecules, poster number: 254
Recording 13C-15N HMQC 2D spectra in solids in 30 sec
Eriks Kupce1; Julien Trebosc2; Barbara Perrone3; Olivier Lafon4; Jean Paul Amoureux5
1Bruker UK Ltd, Coventry, United Kingdom; 2Université de Lille - UCCS-CNRS UMR8181, Villeneuve D'ascq Cedex, N/A; 3Universitiy of Padova, Padova, N/A; 4University of Lille 1, Villeneuve D'ascq Cedex, N/A; 5Lille university and ECNU Shanghai, Villeneuve D'ascq, France

We present a dipolar HMQC Hadamard-encoded (D-HMQC-Hn) experiment for fast acquisition of 2D correlation spectra of abundant nuclei in solid state. The main “bottleneck” of the Hadamard technique in solids resides in the length of the encoding pulses. This leads to a compromise between the selectivity and the sensitivity due to the associated relaxation losses. For this reason, these methods should mainly be used with sparse spectra, and they profit from the increased separation of the resonances at high magnetic fields. The technique has been demonstrated on a fully 13C,15N labelled f-MLF sample. The build-up curves of the 13C-15N cross-peaks were obtained from 13 2D D-HMQC-Hn spectra within 10 min.


Session: Small Molecules, poster number: 255
Characterization of Non-Aqueous Phase Liquids and Contaminated Soils Using Nuclear Magnetic Resonance Spectroscopy
Darcy Fallaise1; Julie Konzuk2; Erin Mack3; James Longstaffe1
1University of Guelph, Guelph, Canada; 2Geosyntec Consultants, Toronto , Canada; 3E.I. du Pont de Nemours and Company, Wilmington, United States
The accurate characterization of environmental contaminates is critical when developing accurate risk assessment and efficient/effective remedial strategies. Relying on conventional analytical approaches for characterization can lead to gaps in the understanding of the composition of complex environmental mixtures, as these approaches tend to focus on target compound identification, and therefore miss potential degradation compounds or compounds where analytical standards do not exist. Employing NMR as a tool to characterize the chemical constituents within an environmental contamination sample will be advantageous. With the development of more selective single and multidimensional experiments, the elucidation of structures can become quicker and more accurate. With increased efficiency and efficacy, NMR can be used as an environmental screening tool in the field of environmental remediation.

Session: Small Molecules, poster number: 256
Environmental NMR: Characterization of Mixtures of Chlorinated Aromatics Using Benchtop NMR Spectroscopy in combination with Spectral Predication and Pattern Matching
James Longstaffe1; Darcy Fallaise1; Brent Pautler2
1University of Guelph, Guelph, Canada; 2Advanced Chemistry Development, Toronto, Canada
Accurate knowledge of the compounds present at a contaminated site is needed for the development of meaningful risk assessments and effective management strategies in order to protect and remediate our environment. NMR spectroscopy has many advantages over conventional tools for environmental characterization for the elucidation of the structure of unknown aromatic compounds. Nevertheless, NMR is not routinely used as a practical tool for environmental characterization, owing in large part to the limited access to NMR instrumentation in the environmental industry. This poster presents the use of benchtop NMR, through the application of 1H J-resolved spectroscopy and NMR spectral simulations of higher order coupling patterns, to elucidate the composition of complex mixtures of chlorinated aromatics.

Session: Small Molecules, poster number: 257
Predicting Anisotropic Thermal Displacements from Solid-State NMR
Jim Harper
University of Central Florida, Orlando, FL
NMR crystallography methods can now provide crystal structures for molecules that cannot be solved by conventional diffraction methods.  One deficiency, however, in nearly all NMR derived structures is the inability to estimate errors in the three-dimensional atomic positions (i.e. “thermal ellipsoids”).  This poster describes a 13C NMR method for providing uncertainties for COOH hydrogens in four polymorphs of palmitic acid.  A comparison against benchmark values from x-ray and neutron diffraction indicates that the NMR-derived errors are nearly an order of magnitude smaller than those derived from single crystal x-ray diffraction and roughly two times smaller than errors obtained from single crystal neutron diffraction.

Session: Small Molecules, poster number: 258
An NMR Investigation of Two Structural Analogs of Linolenic Acid
Fu Chen1; Walter F. Schmidt2; Julie K. Nguyen2; Moon S. Kim2
1The University of Maryland, College Park, MD; 2EMFSL, Agricultural Research Service, Beltsville, MD
Two structural analogs of Linolenic acid (α-LN and γ-LN) are each essential C18 fatty acids (FA). Each contains the identical moiety -CH2-(H-C=C-H)-CH2-(H-C=C-H)-CH2-(H-C=C-H)-CH2-. The structural/conformational information of both LNs is important to help understand their functions. One and two dimensional NMR experiments (including H-1, C-13, COSY, HSQC and INADEQUATE) enabled complete assignments for each of the carbon chemical shifts and for the in-part overlapping proton chemical shifts in the neat samples of individual isomers and in the 2:1 mixture. The molecular sites at which conformational changes are occurring in the mixture are identified. A reason why α-LN and γ-LN contain the identical -CH2-(H-C=C-H)-CH2-(H-C=C-H)-CH2-(H-C=C-H)-CH2- moiety alone but the mixture are not conformationally identical is proposed.

Session: Small Molecules, poster number: 259
High-Performance Pulsed Field gradients for applications in MAS Solid-state NMR
Bibhuti Das; Daniel Arcos; Paul Ellis; F. David doty
Doty Scientific, Columbia, SC
Pulsed Field Gradients (PFGs) are widely used in solution NMR for solvent suppression, reducing t1 noise artifacts, gradient-enhanced spectral editing, coherence pathways selection in triple resonance experiments, diffusion weighted spectral editing, and diffusion coefficient measurement, and so on. But, PFG applications are rare in solid state because solids MAS probes are not equipped with gradient coils. Here, we demonstrate the utility of a MAG/MAS prober for solid state NMR. The design, construction and performance of a high-resolution low-E MAS probe optimized for inverse 1H detection in solution and in solids with, gradient coils producing fields up to 500 G/cm. The probe’s rapid gradient recovery time enables acquisition of high-resolution 1H spectra with high-performance solvent suppression, under static and moderate MAS.

Session: Small Molecules, poster number: 260
Generating Unbiased Structural Alternatives for Automated Structure Verification
Sergey Golotvin1; Rostislav Pol1; Mikhail Elyashberg1; Dimitris Argyropoulos2; Karim Kassam3
1ACD/Labs, Moscow, Russian Federation; 2ACD/Labs, Oxford, United Kingdom; 3ACD/Labs, Toronto, Canada
Automated Structure Verification (ASV) using NMR data is gaining acceptance as a routine application for qualitative evaluation of large compound libraries produced by synthetic chemistry. Here we present a method for generating alternative ‘unbiased’ structures for ASV, based on the structure generator used in a CASE system. Using this approach we are able to generate every isomer that fits a particular NMR dataset without using any prior available knowledge. Practical aspects of this ‘unbiased’ verification are discussed and several examples are shown.

Session: Small Molecules, poster number: 261
A Review of the Methodology and Results of Computer Assisted Structure Elucidation (CASE)
David Adams1; Dimitris Argyropoulos2
1ACD/Labs, Toronto, Canada; 2ACD/Labs, Oxford, United Kingdom
Computer Assisted Structure Elucidation (CASE) first appeared in literature almost 50 years ago. It gained significant traction in the past 20 years largely due to the advancements in computing power. In this presentation we review the variety of almost 60 structures solved using a CASE system showing details of the types of structures solved, their sizes in terms of heavy atoms, the proton content, the elucidation time and the confidence level on the result, ultimately giving further evidence that CASE is a reliable and efficient tool for structure elucidation.

Session: Small Molecules, poster number: 262
Boosting the NMR assignment of small to medium-sized molecules with different edited variants of HSQC-CLIP-COSY experiment

Tamás Milán Nagy1; Tamás Gyöngyösi1; Sándor Boros2; Burkhard Luy3; Katalin E. Kövér1
1University of Debrecen, Debrecen, Hungary; 2Vichem Chemie Research Ltd., Budapest, Hungary; 3Karlsruhe Institute of Technology, Karlsruhe, Germany
The recently introduced CLIP-COSY experiment providing homonuclear correlation spectrum with high quality clean in-phase multiplets expedites the assignment of scalar coupled proton spin network and so, the structure elucidation of small and medium-sized molecules. However, the resolution of COSY spectra is limited by the inherently small chemical shift dispersion of proton resonances.
To utilize the resolving power of heteronuclei offered by their superior chemical shift range, we have devised an HSQC-variant of the CLIP-COSY experiment. Herein, we demonstrate that the performance of the original HSQC-CLIP-COSY experiment can be further boosted with incorporation of heteronuclear spin echo block(s), allowing editing of X-nuclei according to even or odd multiplicity and/or editing of direct HSQC correlations vs. CLIP-COSY peaks.

Session: Small Molecules, poster number: 263
Assessing the Binding Modes of Hemilabile Pincer-crown Ether Ligands in Solution using NMR methods
Andrew Camp
UNC Chapel Hill, Chapel Hill, NC
Hemilabile ligands are found in many exceptional catalysts. However, they can shift between multiple coordination modes, complicating characterization of the coordination sphere in solution. A protocol differentiating coordination mode of hemilabile ligands by solution-phase NMR is introduced. Our group has synthesized iridium pincer-crown ether complexes with a hemilabile crown-ether macrocycle, providing a convenient framework to explore changes in coordination mode. NMR methods and crystallographic studies were used to confirm the 3D structure of 5 model complexes. Solution NMR and crystallographic studies reveal that the chemical shift difference between diasterotopic protons (∆) reports on the proximity of the macrocycle to the metal center, allowing differentiation between high- and low-coordinate ligand binding modes with few NMR experiments.

Session: Small Molecules, poster number: 264
Using Predicted 13C NMR Spectra with Open Resources for Structure Dereplication
Dimitris Argyropoulos; Sergey Golotvin; Rostislav Pol; Joe DiMartino; Arvin Moser; Brent Pautler
Advanced Chemistry Development, Toronto, Canada
Dereplication is the practice of screening active compounds early in the development process, to recognize and eliminate compounds that have been previously studied. This enables scientists to focus on testing truly ‘unknown’ compounds. The 13C NMR spectrum of a compound can be considered a fingerprint since it is virtually unaffected by conditions such as pH, concentration, and solvent effects. It is also largely magnetic field independent, since there are no couplings that could cause variations in stronger or weaker fields. Here we explore the possibilities and limitations of using predicted 13C spectra for structures from open databases (PubChem and ChemSpider). The workflow is described together with examples of the results and the potential usefulness of the technique.

Session: Small Molecules, poster number: 265
Insight from 2-Norbornene, α-Pinene and β-Pinene Experiments on the Shielding Effect of Double Bonds
Clark D. Ridge1; Eugene Mazzola2
1FDA, College Park, MD; 2University of Maryland, College Park, MD
Chemical shift and NOE data were used to explore the shielding effects of double bonds. 2-norbornene was used as a model. Comparisons were also done on α- and β- pinene and their saturated counterparts, α- and β-pinane. These comparisons allow the separation of shielding effects and anisotropic ring effects. These model compounds show that the shielding effect of the double bond is greatest in the a cone extending from the pi-orbital and falls off sharply outside the cone. There is also a small exclusion or pushing effect which can be used to explain the shift of the geminal proton that is further away from the double bond.

Session: Small Molecules, poster number: 266
A Multi-CMC Model of Sequential Aggregation Applied to Multinuclear and High Field NMR Chemical Shifts
David Rovnyak; Kyle W. Eckenroad; Gregory A. Manley; Timothy G. Strein
Bucknell University, Lewisburg, PA
Some amphiphiles can undergo multiple, sequential micellization steps as a function of concentration, and the individual steps can be difficult to characterize. We develop a multi-step phase-separation model and apply it to high field (900 MHz) and multinuclear chemical shift titration data to demonstrate sequential CMC’s in diverse bile systems, including probe-free bile salt solutions. Although the phase separation treatments used here forfeit knowledge of aggregation number, it is significant that this approach enables multiple micellization steps to be demonstrated in a single combined modeling of the data, which been elusive to date. This work also finds that NMR chemical shift titrations show sufficient sensitivity to local structure that they can contain enough complexity to justify the multi-CMC model.

Session: Small Molecules, poster number: 267
Molecular Interactions in Pharmaceutical Drug Substances and Products
Investigated by Magic Angle Spinning NMR: A Posaconazole Example

Xingyu Lu1; Chengbin Huang1, 2; Alexei Buevich1; David Hesk1; Chad D. Brown1; Fengyuan Yang3; Athanas Koynov1; Luke Schenck1; R. Thomas Williamson1; Wei Xu1; Yongchao Su1
1Merck Research Laboratories, Merck & Co., Inc., Kenilworth, NJ; 2University of Wisconsin-Madison, Madison, WI; 3Ashland Inc., Wilmington, DE
Molecular interaction between active pharmaceutical ingredients (APIs) and polymeric excipients is one of the critical attributes affecting physicochemical stability, manufacturability, and dissolution kinetics of amorphous formulations and thus warrants detailed investigation in drug development. However, characterization of natural abundance APIs in multicomponent formulations at the molecular level is of great challenge. Solid-state NMR (ssNMR) plays an indispensable role in extracting structural information of pharmaceutical materials at a high resolution. We aim to utilize magic angle spinning (MAS) NMR techniques for a comprehensive analysis of molecular structures and interactions in crystalline drug substances and pharmaceutical products.

Session: Small Molecules, poster number: 268
The Functional Amphotericin B Sponge is Composed of Highly Structured Asymmetric Homodimers
Agnieszka Lewandowska
University of Illinois, Urbana, IL
Amphotericin B (AmB) is a highly powerful antifungal drug that for the past 50 years has been commonly used to treat a wide range of life-threating systematic fungal infections, despite toxic side-effects. To design new AmB derivatives with a higher therapeutic index, an atomic-resolution understanding of AmB assembly is first required. We have previously shown that amphotericin B exists primarily in the form of large, extramembranous aggregates (the “sterol sponge”) that kill yeast by extracting ergosterol from lipid bilayers. Here, we report the preliminary high-resolution structure of amphotericin B in these aggregates and show that the minimal unit of assembly is an asymmetric homodimer.