Stereoretentive conversion of dialkyl [18O]-phosphoranilidates into dialkyl hydrogen [18O]-phosphates

Conversion of P-chiral dialkyl phosphoranilidates into corresponding dialkyl hydrogen phosphates by means of isoamyl nitrite proceeds with retention of configuration at phosphorus.     

The stereochemistry of reaction of P-chiral dialkyl hydrogen phosphorothioates with [18O]-dimethyl sulphoxide

Cis- and trans-2-hydroxy-2-thiono-4-methyl-1,3,2-dioxaphosphorinanes are cleanly transformed by means of [¹⁸O]- DMSO into corresponding 2-([¹⁸O]-oxo)-derivatives with ca 90% inversion of configuration at phosphorus atom.     

Stereospecific conversion of cyclic phosphorothioates into chlorophosphates

The reaction of the individual diastereoisomeric cyclic phosphorothioates 2a, 2b in the trans-2,4,7-trioxa-3-phosphabicyclo (4.4.0) decane and 4a, 4b in the trans-2,4,7-trioxa-3-phosphabicyclo (4.3.0) nonane series with sulphuryl chloride affords the corresponding sulphenyl chlorides 5a, 5b, 6a, 6b with retention of the configuration of the phosphorus atom. The reaction of the latter with phosphorus trichloride leads stereospecifically to the chlorophosphates 7a, 7b, 8a and 8b with full retention of configuration at phosphorus.     

Determination of 17O and 18O isotopic abundances in 238Pu materials by γ-ray spectrometry

A procedure has been developed for nondestructive determinations of ¹⁷O and ¹⁸O isotopic abundances in ²³⁸PuO₂ fuels produced for biomedical application. Close control of these isotopes is important because they increase the neutron emission rate caused by (α, n) reactions. γ-Rays accompanying these reactions are measured by a lithium-drifted germanium [Ge(Li)] detector and related to their respective isotopic abundances. Each determination has a detection limit approximating the lowest contents encountered in PuO₂ samples of 0.005% ¹⁷O and 0.001% ¹⁸O. The average deviations for each determination are estimated to be about ±25% at their detection levels, and less than ± 10% for abundances above 0.01%.     

Untersuchungen zu einer IR-spektrophotometrischen Bestimmung von 15N und 18O

Zusammenfassung ¹⁵N bzw. ¹⁸O aus organischen Verbindungen muß zur IR-Analyse über NH₃ bzw. H₂O in geeignete Substanzen eingebaut werden. NH₃ kann quantitativ im mMol-Bereich durch Reaktion mit Sulfochloriden oder mit Halogen-nitrobenzolen gebunden werden; H₂O addiert sich quantitativ an Carbodiimide oder Inamine.Die Verschiebungen einiger IR-Absorptionsbanden der markierten Reaktionsprodukte werden angegeben. Die Abhängigkeit der Bandenhöhe der Carbonylabsorption des N, N-Di-p-tolyl-harnstoffs vom ¹⁸O-Gehalt wird demonstriert. Die Amplitude der NH-Absorption in Differenzspektren von ¹⁵N-2,4-Dinitro-anilin-Proben gegen ¹⁴N-2,4-Dinitroanilin ergibt eine Eichkurve, die zur Bestimmung des ¹⁵N-Gehaltes von Testsubstanzen benutzt wird. Der Anwendungsbereich des Verfahrens wird diskutiert.

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Investigations on an IR-spectrophotometric determination of ¹⁵N and ¹⁸O

¹⁵N or ¹⁸O from organic compounds must be converted into substances suitable for infra-red analysis via ammonia or water, respectively. NH₃ can be reacted quantitatively in the mmole scale with sulphochlorides or halonitrobenzenes; H₂O adds quantitatively to carbodiimides or inamines.The shifts of some IR-absorption bands of the labelled reaction products are given. The dependence of the carbonyl adsorbancy of N,N-di-p-tolyl-urea on the ¹⁸O-content is demonstrated. Prom the amplitude of the N-H-absorption in difference spectra of ¹⁵N-2,4-dinitro-aniline samples against ¹⁴N-2,4-dinitroaniline a calibration curve is obtained, which can be used for determining the ¹⁵N content of test substances. The scope of the method is discussed.

     

Vibrational energy transfer between 12C16O and 13C16O

The rate of the energy exchange process ¹²C¹⁶O (v= 1)+ ¹³C¹⁶O (v= 0) ? ¹²C¹⁶O (v= 0) +¹³C¹⁶O (v= 1) + 47.2 cm^?1 has been measured by laser-induced fluorescence, k₂ = (7.2 ± 0.3) × 10⁴ s^?1 Torr^?1 at 293 K. This result is in reasonable agreement with that predicted by theories based on long-range dipole-dipole interactions     

17O NMR spectroscopy of nucleoside derivatives; bonding characteristics of pyrimidine carbonyls

Various uridine derivatives have been selectively enriched (≈ 50%) at the 04 and 02 oxygens, and the ¹⁷O chemical shifts and linewidths measured. The chemical shifts, which are primarily dependent on π-bond-order and hydrogen bonding, show effects that are selective for the 02 and 04 oxygens. In particular, significantly more H-bonding to D₂O and higher π bond order are found for the 04 oxygen.     

Mechanism of the thermal conversion of tetracyclo[3.3.0.02,4.0.3,6]oct-7-ene into dihydropentalenes

One of a number of possible mechanisms has been established for the title reaction.     

The predictable behaviour of cations deriving from endo-4-chlorotetracyclo[3.3.0.0.2,8O.3,6]octane.

Silver cation-initiated ionization of the title compound in aqueous dioxane gives the exo and endo-tetracyclo[3.3.0.0.^2,8O.^4,6]octane-3-ols (35 and 65%). Thermal isomerization in chloroform gives the exo and endo isomers of 4-chlorobicyclo[3.2.1]octa-2,6-dienes (3.5 and 1.5%) and 6-chlorotricyclo[3.2.1.0.^2,7]oct-3-ene (90 and 5%). The behaviour of the cations involved is compatible with MINDO/3 calculations.     

Assessment of labelled products with different radioanalytical methods: study on 18F-fluorination reaction of 4-[18F]fluoro-N-[2-[1-(2-methoxyphenyl)-1-piperazinyl]ethyl-N-2-pyridinyl-benzamide (p-[18F]MPPF)

The serotonin receptor 5-HT_1A ligand 4-[¹⁸F]fluoro-N-[2-[1-(2-methoxyphenyl)-1-piperazinyl]ethyl-N-2-pyridinyl-benzamide (p-[¹⁸F]MPPF) was produced by a simplified method of Le Bars et al. Traditional oil bath heating was compared to microwave heating. Various radioanalytical methods, radio-Thin Layer Chromatography (TLC), High Pressure Liquid Chromatography (HPLC) and Mass Spectrometry (MS), were compared in the evaluation of the labelled product(s). The crude reaction mixture consisted of p-[¹⁸F]MPPF and 2–4 radioactive by-products eluting after the product fraction, and the reverse-phase HPLC method failed occasionally to separate p-[¹⁸F]MPPF from the radioactive by-product with close retention time. The heating method had no significant effect on the composition of labelled by-products. In LC-(ESI)-MS analysis of p-[¹⁸F]MPPF the labelled product was identified with m/z ratio of 435 ([M + H⁺]). The other HPLC fractions were measured to have following m/z ratios: (1) 327; 349; (675) (2) 402; 407/408; (791) and (3) 436, suggesting different kind of decomposition of the labelled product and/or the inactive precursor. The ion trap mass spectrometer was sufficient for the qualitative analysis of p-[¹⁸F]MPPF. However, differentiation of by-products arising from the decomposition of p-[¹⁸F]MPPF or from its precursor p-MPPNO₂ proved to be challenging.     

Module-assisted one-pot synthesis of [18F]SFB for radiolabeling proteins

The need of reliable production of N-succinimidyl 4-[¹⁸F]fluorobenzoate ([¹⁸F]SFB), a versatile ¹⁸F-labeled prosthetic group for protein labeling, has increased dramatically due to the easy availability of proteins or their engineered derivatives for targeted molecular imaging. A module-assisted radiosynthesis of [¹⁸F]SFB was developed using a three-step, one-pot procedure and ethyl 4-(trimethylammonium)benzoate triflate (1) as the starting material. The radiochemical transformations were carried out in a general-purpose, custom-made module and streamlined by an anhydrous deprotection strategy using t-BuOK/DMSO. After HPLC-purification, [¹⁸F]SFB was synthesized in radiochemical yields of 20–30% (n > 10, not decay-corrected) and excellent radiochemical and chemical purities (>98%). The total synthesis and purification time required is ~90 min. Using the purified [¹⁸F]SFB, three ¹⁸F-labeled proteins, bovine serum albumin (BSA), chicken egg albumin (CEA) and transferrin, were synthesized in yields of 61.0–79.5%. The ¹⁸F-Annexin V for apoptosis imaging was also produced in 5% radiolabeling yield and >95% radiochemical purity.     

Pyrolyse thermique des [14C] et [3H] ortho et para-cresols

The thermal cracking of ortho and para-cresols labelled in specific position with [¹⁴C] and [³H] shows that the formation of water and methane are directly related to the formation of toluene and phenol respectively. On the other hand, the formation of benzène results from a rearrangement to a cycloheptatriene followed by elimination of carbon monoxide, produced quasi exclusively by loss of the carbon supporting the hydroxyl function. The minor products involve either a C₅ intermediate (cyclopentadiene), or a C₆ analogue (methylcyclopentadiene). The carbon supporting the hydroxyl group is not involved in the formation of minor products.     

17O-enriched α-azohydroperoxides: 17O NMR spectroscopy, 17O-labeling reagents

¹⁷O-enriched α-azohydroperoxides, prepared by autoxidation, are efficient ¹⁷O-labeling reagents; ¹⁷O NMR (CD₃CN) of 2 showed broad signals at δ 254 and 204 PPM; the solvent dependence of the ¹⁷O chemical shifts and the kinetics of ionic oxidations are interrelated.     

立方Nd2O3上过氧物种光诱导生成的18O同位素示踪考察

采用原位显微Raman光谱和¹⁸O同位素示踪技术,以325 nm激光为激发光源,对立方Nd₂O₃上过氧物种的光诱导生成过程进行了详细表征,进一步证实过氧源于分子氧对晶格氧的氧化反应. 结果还表明,325 nm激光在室温下即可诱导过氧的生成,在实验条件下,生成的过氧物种可与Nd₂O₃的晶格氧发生快速的氧交换反应,位于Nd₂O₃体相的晶格氧也可迁移至样品表层进而参与过氧的生成. 325 nm激光照射有助于促进晶格氧的迁移以及晶格氧与分子氧之间的氧交换反应.     

Zur kenntnis von [O2]+[Mn2F9]−

[O₂]⁺[Mn₂F₉]^? has been prepared for the first time by reaction of MnO₂ or MnF_x (x = 2,3,4) with a mixture of fluorine and oxygen (P_F2/O₂ ≈ 300–3500 atm., t ≈ 350–550°C) either as a dark red powder or as ruby red needles or plates. From single crystal studies the space group is C2/c - C⁶_2h (No. 15) with a = 17.55₂, b = 8.37₃, c = 9.10₁ Å, β = 102.3°, Z = B (at ?150°C). The crystal structure has been refined to R = 0.053 (1619 unique reflections). From the structure determination [O₂]+[Mn₂F₉] has ‘mänder’ like bands of double chains of [MnF₆] octahedra, which are stacked up in layers parallel to (100) with O₂⁺-cations (d_0?0 = 1.10₀ Å) located between the layers. ν_O2 is at 1838 cm^?1 and the magnetic moment μ_eff = 5.63 B.M. is as expected for a ‘spin only’ case without spin-spin interaction.     

2-azatricyclo[2.2.1.01,6]heptane: Synthesis and conversion to 2-azabicyclo[2.2.1]heptanes

A facile route to 6-substituted 2-azabicyclo[2.2.1]heptanes via the novel tricyclic system, 2-azatricyclo[2.2.1.0^1,6]heptane (2), is described. The key intermediate (2) was prepared by oxidation of 4-aminomethylcyclopentene with lead tetra-acetate, and the bicyclic system was obtained by reaction of acetate with 2.MeI. Equilibration of exo- and endo-6-hydroxy-1-methyl-2-azabicyclo[2.2.1]heptane afforded an exo-endo isomeric ratio close to that of norborneol, and on this basis it is suggested that the steric requirements of the nitrogen lone pair are similar to that of CH.     

17O NMR spectroscopy of transition metal carbonyls

NMR spectra of ¹⁷O in natural abundance have been obtained for a range of metal carbonyls. Linewidths of less than 10 Hz for the derivatives of Cr, Mo, W and Fe have been observed, although they are slightly larger for the derivatives of metals having an electric quadrupole moment. Comparison with the corresponding ¹³C NMR data shows that: (i) the chemical shift ranges are comparable, (ii) the ordering of chemical shifts is not very different, (iii) the linewidths are more favourable for ¹⁷O than ¹³C for some Mn and Co derivatives and allow an extension of the range of temperature in which information on the fluxional dynamics are obtainable in the rapid exchange limit.     

CO LMR spectrum of14N16O and its analysis with spectra of14N17O and14N18O

LMR spectra for v=1←0 transitions of¹⁴N¹⁶O in X²II_{1/2, 3/2} states were observed at 5.6 μm and 5.4 μm of CO laser. Introducing the advanced isotopic molecular constant scaling function to Hund’s case (a) diatomic structure model, these spectra were analyzed and fitted together with all reliable previous spectral data of¹⁴N¹⁶O as well as¹⁴N¹⁷O and¹⁴N¹⁸O. A full set of precise molecular parameters and their vibrational dependencies have been determined with much higher precision (1–2 orders for most parameters). Many of them have been obtained for the first time. Using isotopic scaling function, the molecular constants of¹⁴N¹⁷O and¹⁴N¹⁸O were deduced.     

17O and 183W NMR studies of the paratungstate anions in aqueous solutions

¹⁷O (40.7 MHz) and ¹⁸³W (12.5 MHz) NMR spectra of aqueous Na₁₀[H₂W₁₂O₄₂]·27H₂O (1), Na₆[W₇O₂₄]·14H₂O (2) and (NH₄)₆[Mo₇O₂₄]·nH₂O solutions, as well as of 2, 1 and 0.1 M Na₂WO₄ and 2 M Li₂WO₄ solutions acidified up to P = 0.5, 1 and 1.14 have been measured. The composition of the W₇O₂₄^6? anion remains unchanged (2), its structure being similar to that of Mo₇O₂₄^6?183W NMR spectrum shows three resonances with the chemical shifts + 269.2, ?98.8 and ?178.9 ppm relative to WO₄^2? and intensity ratio 1:4:2. “Paratungstate A” produced during polycondensation of WO₄^2? at P ? 1.17 is identical with heptatungstate W₇O₂₄^6?. The [H₂W₁₂O₄₂]^10?183W NMR spectrum in the acidified 2 M Li₂WO₄ solution has four resonances with the chemical shifts in the range - 105–145 ppm and intensity ratio 1:2:1:2. As suggested by NMR data, the H₂W₁₂O₄₂^10? ? W₇O₂₄^6? transformations occur, which depend upon concentration and temperature.     

15N and 17O NMR spectra of some nitrogen- and oxygen-containing polyfluoroaromatic compounds

The effect of substitution of hydrogen by fluorine on the ¹⁵N and ¹⁷O NMR chemical shifts in N-sulphinylarylamines, azoxy- benzenes, C,N-diarylnitrones and aromatic azomethines has been studied. Changes in nitrogen screening are controlled mainly by the radial factor <r^?3>_2p(N), which depends on the electron density on nitrogen, those in oxygen screening — by the two factors, the excitation energy ΔE^?1 and the radial factor <r^?3>_2p(0), which may operate in the same or opposite directions. The ¹⁵N and ¹⁷O NMR spectra of the above compounds did not show any specific effects of perfluorination.