X rays, crystal structure

X-Ray crystallographic data for several basic derivatives of H-1,2,3-triazole and benzotriazole are included in CHEC(1984) and CHEC-II(1996) 1984CHEC(5)669, 1996CHEC-II(4)1 . Hundreds of new 1 //-1,2,3-triazole structures have been analyzed since some crystallographic data for representative examples (structures 5-12) are collected in Table 1. 

To illustrate signal assignments in 13C NMR spectra of the benzotriazol-l-yl system, chemical shifts for five a-(benzotriazol-l-yl)tetrahydrofurans (structures 39-43) 2003JP0158 and three corresponding tetrahydropyrans (structures 27-29) 2001CJC1655 are listed in Table 5. Selected 13C NMR spectral data for triazolyl nucleoside analogs 44-50 2003SPL461 are collected in Table 6. 

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Diederich F, Jonas U, Gramlich V, Herrmann A, Ringsdorf H and Thilgen C 1993 Synthesis of a fullerene derivative of benzo[18]crown-6 by Diels-Alder reaction complexation ability, amphiphilic properties, and x-ray crystal structure of a dimethoxy-1,9-(methano[1, 2]benzomethano)fullerene[60] benzene clathrate Helv. Chim. Acta 76 2445-53... 

Bode, W., Papamokos, E., Musil, D. The high-resolution X-ray crystal structure of the complex formed between subtilisin Carlsberg and eglin c, an elastase inhibitor from the leech Hirudo medicinalis. Eur. J. Biochem. 166 (1987) 673-692... 

Frazao C, C Topham, V Dhanaraj and T L Blundell 1994. Comparative Modelling of Human Rer Retrospective Evaluation of the Model with Respect to the X-ray Crystal Structure, Pure and A Chemistry 66 43-50. 

D, H W Hoeffken, D Crosse, J Stuerzebecher, P D Martin, B F P Edwards and W Bode 1992. Refined 2.3 Angstroms X-Ray Crystal Structure of Bovine Thrombin Complexes Formed witli he 3 Benzamidine and Arginine-Based Thrombin Inhibitors NAPAP, 4-TAPAP and MQPA A Starting Point for Improving Antithrombotics. Journal of Molecular Biology 226 1085-1099. 

D, J Sturzebecher and WBode 1991. Geometry of Binding of the N-Alpha-Tosylated Piperidides of weffl-Amidino-Phenylalanine, Para Amidino-Phenylalanine and para-Guanidino-Phenylalanine to Thrombin and Trypsin - X-ray Crystal Structures of Their Trypsin Complexes and Modeling of their Thrombin Complexes. FEBS Letters 287 133-138. 

An impressive example of the application of structure-based methods was the design of a inhibitor of the HIV protease by a group of scientists at DuPont Merck [Lam et al. 1994 This enzyme is crucial to the replication of the HIV virus, and inhibitors have bee shown to have therapeutic value as components of anti-AIDS treatment regimes. The star1 ing point for their work was a series of X-ray crystal structures of the enzyme with number of inhibitors boimd. Their objective was to discover potent, novel leads whid were orally available. Many of the previously reported inhibitors of this enzyme possessei substantial peptide character, and so were biologically unstable, poorly absorbed am rapidly metabolised. 

X-ray crystal structure, 6, 516 Benzophenanthridines synthesis from anils, 2, 416 Benzophenanthridines, tetrahydro-synthesis, 2, 469 Benzo[c]phenanthridines synthesis, 2, 414 from aryl isocyanides, 2, 411 from benzynes, 2, 432 Benzo[i]phenanthridines synthesis, 2, 414 Benzophenanthridinones... 

Oxetane, 3,3-bis(trimethylaminomethyl)-methane sulfonate X-ray crystal structure, 7, 365 Oxetane, 3-bromo-synthesis, 7, 390 Oxetane, 2-t-butyl-3-methyl-synthesis, 7, 399 Oxetane, 2-chloro-reactions, 7, 390 Oxetane, 3-chloro-synthesis, 7, 390... 

Oxetane, 2-(o -chlorobenzyl)-2-phenyl-X-ray crystal structure, 7, 366 Oxetane, 3-chloromethyl-3-ethyl-ring strain, 7, 370-371 Oxetane, 2-(o-chlorophenyl)- H NMR, 7, 367 Oxetane, 2-cyano-synthesis, 7, 391-392 Oxetane, 2-cyano-3,3-dimethyl-2-phenyl-thermolysis, 7, 372 Oxetane, 2,2-dialkoxy-synthesis, 7, 396 Oxetane, 2,2-dialkyl-isomerization, 7, 377 Oxetane, 3,3-dialkyl-alkylative cleavage, 7, 381 polymers, 7, 382 Oxetane, 2-diethylamino-synthesis, 7, 390 Oxetane, 3,3-difluoro-molecular dimensions, 7, 365 Oxetane, 2,2-dimethyl-mass spectra, 7, 368-369 photolysis, 7, 373 synthesis, 7, 393 Oxetane, 2,3-dimethyl- H NMR, 7, 366 thermolysis, 7, 372 Oxetane, 2,4-dimethyl-mass spectrum, 7, 369... 

Oxetane-2-methanol, t/ireo-a,3,3,4,4-pentamethyl-3,5-dinitrobenzoate X-ray crystal structure, 7, 365 Oxetane-3-methanol, 3-alkyl-reactions... 

H,6H-Pyridazino[4,5-d]pyridazine-l,5-dione, 4,8-dichloro-2,6-dimethyl-X-ray crystal structure, 3, 333 Pyridazino[l, 2-a]pyridazine-1,4-diones IR spectra, 3, 332... 

Pyrimido[5,4-d]pyrimidine-2,4,6,8-tetrones X-ray crystal structure, 3, 339 Pyrimido[4,5-d]pyrimidine-4-thiones 3, 339... 

Wang, D., Bode, W., Huber, R. Bovine chymotrypsinogen A. X-ray crystal structure analysis and refinement of a new crystal form at 1.8 A resolution. /. Mol. Biol. 

Picot, D., Loll, P.J., Garavito, R.M. The x-ray crystal structure of the membrane protein prostaglandin H2 synthase-1. Nature 367 243-249, 1994. 

Figure 17.12 Ribbon diagram of EMPl bound to the extracellular domain of the erythropoietin receptor (EBP). Binding of EMPl causes dimerization of erythropoietin receptor. The x-ray crystal structure of the EMPl-EBP complex shows a nearly symmetrical dimer complex in which both peptide monomers interact with both copies of EBP. Recognition between the EMPl peptides and EBP utilizes more than 60% of the EMPl surface and four of six loops in the erythropoietin-binding pocket of EBP.

The highly hindered alkene adamantylideneadamantane forms a bromonium ion which crystallizes as a tribromide salt. An X-ray crystal structure (Fig. 6.1) has confirmed the cyclic nature of the bromonium ion species. This particular bromonium ion does not react further because of extreme steric hindrance to back-side proach by bromide ion. 

In the case of phenyllithium, it has been possible to demonstrate by NMR studies that the compound is tetrameric in 1 2 ether-cyclohexane but dimeric in 1 9 TMEDA-cyclohexane. X-ray crystal structure determinations have been done on both dimeric and tetrameric structures. A dimeric structure crystallizes from hexane containing TMEDA. This structure is shown in Fig. 7.1 A. A tetrameric structure incorporating four ether molecules forms from ether-hexane solution. This structure is shown in Fig. 7.IB. There is a good correspondence between the structures that crystallize and those indicated by the NMR studies. 

The NMR spectrum of this compound shows a diamagnetic ring current of the type expected in an aromatic system. X-ray crystal structures of 1 and its carboxylic acid derivative 2 are shown in Fig. 9.2. Both reveal a pattern of bond lengths very similar to that in naphthalene (see p. 534). ... 

The syn isomer can achieve a conjugated system with angles of up to 35° between adjacent p orbitals. The anti isomer is much more twisted. An X-ray crystal structure of the syn isomer shows C—C bond lengths between 1.368 and 1.418 A for the conjugated system (Fig. 9.3). ° The spectroscopic properties of the syn isomer are consistent with considering it to be a delocalized annulene. B3LYP calculations indicate that both the syn and anti structures are stabilized by delocalization, the syn (17.6kcal/mol) more so than the anti (8.1 kcal). ... 

The NMR spectrum of the syn isomer shows evidence of a diamagnetic ring current, based on both the relatively low-field position of the vinylic hydrogens and the upfield shift of the methylene hydrogens. The anti isomer shows much less pronounced shifts. The X-ray crystal structure of the syn isomer shows a moderate level of bond alternation, ranging ftom 1.36 to 1.45 A (Fig. 9.4A). In the anti isomer, bond alternation is more pronounced, vith the double bond in the center ring being essentially a localized double bond (Fig. 9.4B). 

Fig. 9.4. (A) X-ray crystal structure of j> n-tricyclo[8.4.1.F ]hexadeca-2,4,6,8,10,12,14-heptaene. iB) X-ray crystal structure of anti stereoisomer of tricyclo[8.4.1.1 ]hexadeca-2,4,6,8,10,12,14-heptaene-5-carboxylic acid. (Reproduced from Ref 63 by permission of Wiley-VCH.)...

Reductive coupling reaction of fluonnated vinyl iodides or bromides has been used as a route to fluorinated dienes [246, 247, 248, 249, 250. Generally, the vinyl iodide is heated with copper metal in DMSO or DMF no 1 ntermediate perfluorovmy I-copper reagent is detected. Typical examples are shown m equations 163-165 [246, 247, 249. The X-ray crystal structure of perfluorotetracyclobutacyclooctatetraene, prepared via coupling of tetrafluoro-l,2-diiodocyclobutene with copper, is planar... 

P Fluonnation always strongly stabilizes carbamons both by induction and by negative (anionic) hyperconjugaQon, 7 The latter "no-bond resonance has been controversial, but its importance is now well established both theoretically [133, 134] and expenmentally [67] The X-ray crystal structures of salts 8 [fi5] and 9 [136] provide cogent evidence for negative hyperconjugation... 

Renatns, M., Engh, R. A., Stubbs, M. T, et al., 1997. Lysine-156 promotes the anomalons proenzyme activity of tPA X-ray crystal structure of singlechain human tPA. EMBO Journal 16 4797-4805. 

The X-ray crystal structures of many of these complexes have now been determined representative examples are. shown in Fig. 4.11 from which it is clear that, at least for the larger cations, coordinative saturation and bond rhrectionality are far less significant factors than in many transition element complexes. Further interest in these ligands stems from their use in biochemical modelling since they sometimes mimic the behaviour of naturally occurring, neutral, macrocydic antibiotics such as valinomycin, monactin, nonactin, nigericin... 

An X-ray crystal structure of the Pr N-derivative shows the presence of a bent, 2-coordinate P atom, equal P- N distances, and accurately planar 3-coordinaie N atoms as in (c) above.In liquid ammonia ammonolysis also occurs ... 

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