bluuebunny/crossref_metadata_2025_split huggingface dataset:
NMR and diaphragm-cell techniques for the study of molecular dynamics in fluids
Authors: Price W E , Lüdemann H D 
Published: November 2023

Abstract
Nuclear-magnetic-resonance (NMR) spectroscopy has, arguably, become the most powerful and important analytical tool for structural elucidation of chemical compounds. It has completely revolutionized whole areas of chemistry and biochemistry. So it is perhaps not surprising that modern Fouriertransform (FT-NMR) spectroscopy also plays a central role in studies which focus upon intermolecular interactions, dynamics, and their effects upon the fluid state. The importance of FT-NMR spectroscopy in high-pressure molecular-dynamics experiments is due to its noninvasive nature and its versatility; a number of different parameters may be determined to describe various aspects of the motions and intermolecular forces within a system. With a number of modifications to facilitate the application of elevated pressures the whole gamut of modern FT-NMR spectroscopy is potentially available. A detailed description of the theory and the methods will not be given here, since an outline is sufficient for the present purpose; many scholarly expositions are available on the subject, to which readers are directed.1-3 In addition, Section 3 gives a brief description of the range of measurements which can be made using high-pressure NMR techniques based on recent work.
X-ray synchrotron and neutron radiation studies of polycrystalline molecular compounds
Authors: Willis B T M 
Published: November 2023

Abstract
In recent years X-ray synchrotron radiation and pulsed neutron radiation have been used in the study of organic crystal systems. In this paper we shall describe one such study with X-rays (cimetidine) and two studies with neutrons (fullerene and 4-methyl pyridine oxide). All three studies were carried out on powdered samples and gave results which demonstrate the power of high-resolution instruments in solving structural problems in organic crystal chemistry.
Dynamical structure analysis of isomerization in the crystalline state
Authors: Ohashi Yuji 
Published: November 2023

Abstract
A single-crystal-to-single-crystal transformation is very attractive because both structures of the reactant and product are obtained by X-ray analysis using only one crystal. The topochemical process can easily be envisaged. Typical examples reported so far are the [2+2] photocyclo-addition of 2,5-distyrylpyradine (Nakanishi et al. 1977), the photopolymerization of diacetylene derivatives (Enkelmann et al. 1980), the [2+2] photodimerization of 5-benzylidene cyclopentanones (Nakanishi et al 1981), and the thermal dimerization of o-benzenedithiol cobalt complex (Miller et al. 1983). In all cases the reactions proceed while almost retaining the single crystal form and the movement of each atom can be presumed from the structures before and after the reaction. The composite diagram of the reactant and product structures is very informative. However, the reaction does not always proceed smoothly, that is, obeying first-order kinetics, from the initial stage to the final stage. Determination of the structures at several intermediate stages are essential for elucidating the reaction process. Moreover, a systematic analysis of related crystals is necessary to obtain a quantitative mechanism.
Conformational preferences of (R,R)tartaric acid esters and amides: hydrogen bonding and packing in crystals
Authors: Szczepańska B , Rychlewska U 
Published: November 2023

Abstract
Tartaric acid and its derivatives have long played an important role in the development of organic and pharmaceutical chemistry. Optically active tartaric acid and its 0,0-dibenzoyl derivatives have been used successfully as resolving agents for racemic mixtures and recently (R,R)-tartaric acid diamides have been applied for this purpose (Dobashi, Hara & Iitaka, 1988). This group of compounds has been extensively studied by X-ray crystallography (more than 200 entries are available in the Cambridge Crystallographic Data File). However great in number, crystal structure analyses are limited to various forms of tartaric acid, its metallic and other salts and to compounds containing coordinated tartrate or tartramide ligands. Since, on the other hand, few structural data are available for uncomplexed (R,R)-tartaric acid esters and amides, we have undertaken X-ray studies on this group of compounds. In view of the common use of some of these compounds as resolving agents, investigation of the possible mechanism of their self-association might be of significance. For most of the molecules in question, the dominant mechanism is hydrogen bonding.
Aza-oxa crowns
Authors: Parker David 
Published: November 2023

Abstract
The saturated aza-oxa crown ethers were first synthesised as intermediates in the synthesis of the nitrogen cryptands. The reaction conditions used for the formation of these macrocycles involved the high-dilution technique. In this versatile method, a diamine and a diacid chloride are simultaneously added in the presence of triethylamine to a large volume of solvent, usually toluene, over an extended period of time. The major product from such a reaction is the [1+1] cyclised product, although the [2+2] adduct can often be isolated as well, in low yield. Whilst this method is still sometimes used, particularly for cryptand synthesis (Chapter 5), it has been superseded by methods that are more convenient and which proceed under medium dilution.
Matrix isolation-an introduction to the technique
Authors: Dunkin Ian R 
Published: November 2023

Abstract
In the most general sense, matrix isolation comprises a range of experimental techniques in which guest molecules or atoms are trapped in rigid host materials. The trapped species are prevented from diffusing, and cannot therefore undergo any bimolecular reactions, except with the host (Fig. 1.1). The host material can be a crystalline solid, a polymer, or a glass formed by freezing a liquid or solidifying a gas. The term matrix isolation is, however, most commonly used in a narrower sense: to refer to the technique of trapping molecules or atoms in solidified inert (or occasionally reactive) gases-a technique requiring very low temperatures.
distributed multipole expansions
Authors: Stone A J 
Published: November 2023

Abstract
For those readers accustomed to the concept of radius of convergence as it applies to a series in powers of a complex variable, it is worth emphasising that we are dealing here with a series in powers of 1/ R. For this reason, the interior of the sphere describes the region where the series diverges, and we shall use the term ‘divergence sphere’ to emphasize this fact. In contrast to the case of a circle of convergence in the theory of complex variables, which one wishes to be as large as possible, we require the spheres of divergence to be as small as possible for optimum convergence.
Practical Models For Intermolecular Potentials
Authors: Stone A J 
Published: November 2023

Abstract
The computation of the interaction energy ab initio is very time-consuming, whether it is done by perturbation theory or the supermolecule method, and it is not practical in many applications. In molecular dynamics, for instance, it is necessary to calculate the forces and torques on all the molecules in an assembly of several hundred, in order to obtain the equations of motion, and this has to be repeated for each step in the simulation, which typically requires 105 or 106 steps. For this sort of problem, we usually need to use much simpler models of the interaction. For the most basic properties of condensed phases, it is sufficient to use extremely simple models-for example, the hard-sphere model provided much useful information about the behaviour of inert-gas liquids-but if we want more detailed information, we have to use better models.
Total Synthesis of (±)-Leuhistin
Authors: Hecker S J , Werner, K M 
Published: November 2023

Abstract
Discussion Points Suggest a possible reason for the selectivity observed in step e. Explain the migration of the benzoate group observed in transforming compound 4 into 5. Further Reading For the use of activated alumina in the synthesis of 3-oxoesters, see: D. D. Dhavale, P. N. Patil and R. S. Raghao, J. Chem. Res., Synop.,1994, 4,152. For reviews on catalytic transfer hydrogenation, see: R. A. Johnstone, A. H. Wilby and I. D. Entwistle, Chem. Rev.,1985, 85,129; G. Brieger and T. J. Nestrick, Chem. Rev.,1974, 74,567.
Total Synthesis of 1233A
Authors: Wovkulich P M , Shankaran K , Kigiel J , Uskokovic, M R 
Published: November 2023

Abstract
Discussion. Points Total Synthesis of 1233A What is the mechanism of the Noyori catalyst-mediated asymmetric hydrogenation step a? Explain the diastereoselectivity observed in the [2,3]-rearrangement of step i. During the hydroboration step, a substantial amount of compound 13 was formed. Suggest a way to convert it into the desired epimer 8 by exploiting the latent symmetry of the system. Further Reading For the influence of trace amount of acid in the ruthenium (11)-BINAP catalysed asymmetric hydrogenation, see: S. A. King, A. S. Thompson, A. O. King and R. T. Verhoeven, J. Org. Chem.,1992, 57, 6689. For a review on enantioselective catalysis with transition metal compounds, see: H. Brunner, Quim. Nova,1995, 18,603. For reviews on the [2,3]-Wittig sigmatropic rearrangement, see: K. Mikami and T. Nakai, Synthesis,1991, 8,594; K. Mikami and T. Nakai, Chem. Rev,1986, 86,885. For a review on the carbometalation of alkynes, see: E. Negishi, Pure Appl. Chem.,1981, 53,2333.
Enantioselective Total Synthesis of (-–)-7- Deacetoxyalcyonin Acetate
Authors: MacMillan D W C , Overman, L E 
Published: November 2023

Abstract
Discussion Points Suggest a structure for compound 4 and a possible way of synthesising it from 14. Explain the stereoselectivity observed in step e. Suggest a mechanism for the formation of compound 7. Which enantiomer of diethyl tartrate is necessary to use in order to obtain compound 9? Give an explanation of the regioselectivity obtained in the epoxide reduction of step k. Further Reading For another application of the Prins-pinacol rearrangement, see: G. C. Hirst, T. 0. Johnson and H. E. Overman, J. Am. Chem. Soc.,1993, 115,2992. For a recent review on the Sharpless epoxidation reaction, see: A. D. Gupta, D. Bhuniya and V. K. Singh, J. Indian Inst. Sci.,1994, 74,71. For a review on the Nozaki-Hiyama reaction, see: P. Cintas, Synthesis, 1992, 248. For a review of the use of TPAP as a catalytic oxidant, see: S. V. Ley, J. Norman, W. P. Griffith and S. P. Marsden, Synthesis,1994, 639.
Total Synthesis of (+)-Stoechospermol
Authors: Tanaka M , Tomioka K , Koga, K 
Published: November 2023

Abstract
Discussion Points What is the mechanism of step b? Bearing in mind the fact that the 1:1 diastereomeric mixture 2 gave an approximately 1:1 mixture of isomers 3 and 4, rationalise the stereoselectivity of the reaction and the formation of the four new chiral centres. Propose a reaction sequence which could convert the dilactone isomer 4 into compound 7. What is the mechanism of the reduction with hydrazine hydrate in steps k ands? In step w, DIBAL-H is used to reduce an cx,(3-unsaturated ketone to an allylic alcohol. What reagent is usually used for such a transformation? Explain the stereoselectivity of this step. In the epoxidation of compound 14, why is the cx-epoxide the major isomer? In step e’, a tosylate is sucessfully displaced by an incoming malonate nucleophile with inversion of configuration. What is a potentially significant side-reaction when treating secondary tosylates with more basic nucleophiles? Suggest a mechanism for the reduction step f’. Further Reading A racemic approach to stoechospermol has also been reported recently: M. Miesch, A. Cotte and M. Franck-Neumarm, Tetrahedron Lett.,1994, 35,7031.
Total Synthesis of (+)-Carbonolide B
Authors: Keck G E , Palani A , McHardy, S F 
Published: November 2023

Abstract
Discussion Points The workup of step b includes washing with a saturated solution of Rochelle’s salt. What is the purpose of this process? Suggest a structure for compound S. Rationalise the stereochemistry of the nucleophilic attack on compound 4 in step e. What role does the magnesium bromide etherate play in the stereocontrol? Propose a short synthesis of the alcohol used to esterify compound 10 starting from commercially available (R)-ethyl (3-hydroxybutyrate. Further Reading For a review of macrocyclic ring formation methods, see: Q. C. Meng and M. Hesse, Top. Curr. Chem.,1991, 161,107. For a review of the use of tetrapropylammonium perruthenate (TPAP) see: S. V. Ley, J. Norman, W. P. Griffith and S. P. Marsden, Synthesis, 1994, 639. For a review, in English, of computer-aided conformational design in macrolide synthesis (including carbonolides) see: 0. Yonemitsu, Yuki Gosei Kagaku Kyokaishi,1994, 52,946. The use of ultrasound to accelerate the hydroboration of double bonds has also recently been reported by H. Oguri, S. Hishiyama, T. Oishi and M. Hirama, Synlett,1994, 1252. For a more general review on the application of ultrasound to synthesis see: C. Einhorn, J. Einhorn and J.-L. Luche, Synthesis,1989, 787.
Total Synthesis of Stenine
Authors: Chen C -Y , Hart, D J 
Published: November 2023

Abstract
Discussion Points Propose a structure for the other potential diastereoisomer arising from the intramolecular Diels-Alder cycloaddition. What is the mechanism of the Hoffman-type degradation of step f? A substantial amount of compound 14 is recovered if the Claisen rearrangement is attempted without selective protection of the primary hydroxyl group formed in step p. Further Reading For a review on diastereoselective Claisen rearrangements, see: H.J. Altenbach, Org. Synth. Highlights,1991, 115. For a study of Diels-Alder reaction on trienic esters in the absence and presence of a Lewis acid catalyst, see: M. Toyota, Y. Wada and K. Fukumoto, Heterocycles,1993, 35,111. For a recent NMR study of Lewis acid stoichiometry in Diels-Alder reactions, see: I. R. Hunt, C. Rogers, S. Woo, A. Rauk and B. A. Keay, J. Am. Chem. Soc., 1995, 117, 1049; I. A. Hunt, A. Rauk and B. A. Keay, J. Org. Chem.,1996, 61,751. For a recent article on iodolactonisation leading to 7- to 12-membered ring lactones, see: B. Simonot and G. Rousseau, J. Org. Chem.,1994, 59,5912.
The Total Synthesis of (+)-Adrenosterone
Authors: Dzierba C D , Zandi K S , Mollers T , She.a, K J 
Published: November 2023

Abstract
Discussion Points When ethylene glycol was used instead of (-)-hydroxybenzoin (step e) in the preparation of the silicon tether, the intramolecular Diels-Alder reaction of step h proceeded with reverse diastereoselectivity, affording a mixture corresponding to 6:7 in a 1:10 ratio. Give an explanation for this finding. Further Reading For a review on silicon-tethered reactions, see: M. Bois and T. Skrydstrup, Chem. Rev.,1995, 95,1253.
Total Synthesis of (+)-7-Deoxypancratistatin
Authors: Keck G E , McHardy S F , Murry, J A 
Published: November 2023

Abstract
Discussion Points What is the mechanism of step i? The stereochemical outcome of the radical cyclisation step o is highly dependent on the use of a cyclic precursor (e.g. 7). When acyclic compound 12 was submitted to the same reaction conditions as in o, it cyclised to give 13. Give reasons for this finding.
Total Synthesis of (3Z)-Dactomelyne
Authors: Lee E , Park C M , Yun, J S 
Published: November 2023

Abstract
Discussion Points Explain the mechanism of step b. Explain the cis-2,6-selectivity observed in the radical cyclisation steps h and s. The gem-dichloro derivative obtained in step h could only be reduced stereoselectively with the use of a (trimethylsilyl)silane-triethylborane system. A variety of other systems only led to mixtures. Suggest a possible reason for this finding. Give a reason for the regioselectivity observed in the reductive cleavage of the benzylidene group in step I. In the radical cyclisation step s, none of the epimeric bromide was formed. When the reaction is applied to the synthesis of monocyclic products mixtures of epimers are usually obtained. Give an explanation for this difference in stereoselectivity. What is the mechanism of the Py•SO3 oxidation? Explain the selective formation of the Z double bond in 12.
Synthesis of a Vindorosine Precursor
Authors: Winkler J D , Scott R D , Williard, P G 
Published: November 2023

Abstract
Discussion Points What is the mechanism of the protection sequence a, b? Explain the steroselectivities observed in the photochemical reaction of step f and in the Mannich reaction step g. What is the purpose of tetrabutylammonium fluoride in step h? What is the byproduct of step k? Further Reading For reviews on tandem reaction in the synthesis of natural products, see P. J. Parsons, C. S. Penkett and A. J. Shell, Chem. Rev.,1996, 96,195; J. D. Winkler, C. M. Bowen and F. Liotta, Chem. Rev.,1995, 95,2003.
Total Synthesis of (–)-Parvifforin
Authors: Hoye T R , Ye, Z 
Published: November 2023

Abstract
Discussion Points What kind of symmetry do the molecules from 4 to 6 and from 9 to 15 possess? Which isomer of diethyl tartrate would be expected to give the desired product in step e? In steps i and j the diol 5 is transformed into its corresponding bis­epoxide 6. What product could reasonably have been expected had 5 been first desilylated, then treated as in steps o to q?
The International Classification of Headache Disorders (ICHD)*
Authors: Olesen J 
Published: November 2023

Abstract
Undoubtedly, most physicians consider disease classification to be boring, impossible to learn by heart, and clinically not very useful. This may be true in the sense that practicing physicians do not know classifications or diagnostic criteria by heart and do not even have time to look the criteria up except in special cases. However, we are all working on the basis of some sort of classification and use some sort of diagnostic criteria, often without knowing it.
Discussion Summary, the Secondary Headaches: Part II
Authors: Olesen J 
Published: November 2023

Abstract
The new entity cerebral venous sinus stenosis has been diagnosed in patients with the new persisting headache and increased intracranial pressure by lumbar puncture. In such patients, a stenosis of one or both of the transverse sinuses has been demonstrated. In the experience of Professor Diener, some of these cases were cured by balloon dilatation while, in others, it was not possible to dilate the sinus. The syndrome is still too new to give further details about clinical characteristics and treatment results.
French Survey Network on Headaches and Facial Pains
Authors: Lantéri-Minet M , Autret A , Baudesson G , Bousser M G , Creach’ C , Donnet A , Dousset V , Fabre N , Giraud G , Guégan-Massardier E , Guy N , Lucas C , Massiou H , Mick G , Navez M , Pradalier A , Radat F , Valade D , Géraud G 
Published: November 2023

Abstract
The Société Française d’Etudes des Migraines et Céphalées (SFEMC), i.e French Headache Society, sets up a survey network on headaches and facial pains based on International Headache Society diagnostic classification. We present the main purposes of the network, the methodology, the results after one year, and prospective for 2004.
Microbes In The Pathogenesis Of Rheumatoid Arthritis
Authors: Toivanen Paavo 
Published: November 2023

Abstract
Many diverse concepts and speculations related to the etiopathogenesis of rheumatoid arthritis have been proposed, most of which implicate both genetic and environmental factors. The disease is known to be associated with certain HLA-DRB1 alleles, encoding a common sequence of five amino acids in the hypervariable region of the HLA-DR chain, the so-called susceptibility epitope. This epitope is found in 80–90% of Caucasoid patients with rheumatoid arthritis and in 40–50% of non-rheumatoid subjects. Disease heritability is estimated to be about 60%, of which HLA accounts for less than a half, and multiple loci outside the HLA region are responsible for the rest . Several alternative possibilities have been proposed for the participation of the susceptibility epitope , the most common being that it specifies HLA-DR molecules binding arthritogenic peptides. Recently it has become apparent that bacterial colonization of the host could be determined by genetic factors, including HLA, leaving a novel role also for the susceptibility epitope .
The Role Of T Lymphocytes In Rheumatoid Arthritis
Authors: Fox David A 
Published: November 2023

Abstract
The concept that T cells might be important to the pathogenesis of rheumatoid arthritis (RA) is relatively recent. It was little more than 25 years ago that initial evidence was provided that the preponderance of lymphocytes in synovial tissue were in fact T cells, and not antibody-producing cells. A detailed understanding of T cell biology began to take shape in the 1980s, in large part due to the development of monoclonal antibodies against a variety of lymphocyte surface structures. In parallel with these advances in basic immunology, the hypothesis for a central role of T lymphocytes in a variety of immune-mediated diseases, such as rheumatoid arthritis, begin to take shape . Data from animal models and from genetic studies were also important factors in the development of a ‘T cell hypothesis’ for the pathogenesis of RA.
Angiogenesis And Cell Trafficking
Authors: Buckley Christopher D , Filer, Andrew , Pitzalis Costantino 
Published: November 2023

Abstract
Histologically, the rheumatoid synovium is characterized by a number of defining factors. Critical amongst these are lining layer hyperplasia, accompanied by significant new capillary growth from existing blood vessels (angiogenesis), and infiltration of the hypertrophied synovium by specific, well-defined populations of mononuclear leukocytes. Antigenic vessel formation occurs in the rheumatoid arthritis (RA) synovium, and is considered to be pivotal to the early development and persistence of disease, maintaining supplies of nutrients and cytokines to the expanded lining layer and pannus tissue . Furthermore, the expanded endothelial cell population generated during angiogenesis performs a number of important pathological roles, including cytokine production, coagulation, antigen presentation, and leukocyte recruitment .
Nsaids And Analgesics
Authors: Day Richard O , March Lynette M , Graham Garry G , Scott, Kieran F , Williams Kenneth M 
Published: November 2023

Abstract
The non-steroidal anti-inflammatory drugs (NSAIDs) and related drugs can be divided into two major groups (reviewed in Refs 1 and 2). Non-selective NSAIDs, such as aspirin, ibuprofen and indomethacin, which also produce gastrointestinal damage, inhibit the aggregation of platelets, decrease kidney function in some patients, and precipitate aspirin-induced asthma (Table 22.1). These drugs inhibit both cyclooxygenase-1 (COX-1) and COX-2 which are central enzymes involved in the synthesis of prostaglandins and related compounds.
The New Frontiers In Pathogenesis And Treatment: Methotrexate And Leflunomide
Authors: Rau Rolf 
Published: November 2023

Abstract
In 1947, aminopterin was synthesized as an antifolate for the treatment of tumors. Four years later, Gubner1 reported the successful treatment of seven patients with rheumatoid arthritis (RA) with aminopterin. Methotrexate (MTX) (amethopterin), synthesized in 1948, proved to be less toxic than aminopterin and more feasible for longer term treatment. However, because of the dramatic effects of corticosteroids in the treatment of RA, few rheumatologists were interested in MTX. The first pilot studies only appeared in the early 1980s, encouraging a systematic evaluation of low-dose MTX treatment in RA.