Azidocarbonyl-substituted cubanoureas

Despite the angular strain associated with the assembly of small rings, 1,2-diisocyanatocubane reacts with trimethylsilyl azide under mild conditions to form a hexacyclic ring assembly that contains an imidazolidone ring fused to one edge of cubane. This compound was identified as an azidocarbonyl-substituted cubanourea by means of X-ray crystal structure analysis of the nitro-derivative, the energetic compound N-azidocarbonyl-N¹-nitrocubanourea.     

Localized in vivo proton spectroscopy of the bone marrow in patients with leukemia

Volume selective magnetic resonance (MR) proton spectroscopy was used to investigate the haemopoietic (iliac bone) and fatty bone marrow (tibia) in patients with leukemia and polycythaemia vera. Selective measurements of the relaxation times T₁ and T₂ for the “water” and “fat” resonances in the bone marrow spectra were performed. Nine patients with acute leukemia and three patients with chronic leukemia were examined at diagnosis. Three patients with acute leukemia in remission were also examined. Five of the leukemic patients had follow-up examinations performed in relation to chemotherapeutic treatment. Nine patients with polycythaemia vera and 21 normal control subjects were examined with identical methods for comparison. All patients had bone marrow biopsies performed prior to every MR examination. Significant differences could be detected in the spectral patterns from iliac bone marrow in patients with leukemia at diagnosis compared to the healthy normal controls. The “relative water content” was increased in the iliac bone marrow spectra of the leukemic patients compared to the normal subjects, which indicates an increase in the amount of haemopoietic tissue and a corresponding decrease in marrow fat content. The T₁ relaxation times of the “water” resonance in the spectra from the iliac bone marrow of the leukemic patients were significantly prolonged at diagnosis, compared to the normal controls and the patients with polycythaemia vera. After chemotherapeutic induction of remission, the spectra from the iliac bone marrow in the patients with leukemia resembled normal spectra. Four leukemic patients had abnormal spectra from the tibial bone marrow and one patients showed early changes in tibial marrow during chemotherapeutic treatment, before any major changes could be detected in the iliac bone marrow.     

Estimation of the torsional potential for perfluorodi-methyl ether from electron-diffraction data

A structural model is obtained for perfluorodimethyl ether, based on the assumption of an equilibrium geometry with the effects of internal rotation appearing in the observed vibrational amplitudes. By separation of frame vibrations obtained from a spectroscopie force field, explicit formulae for calculating the torsional contributions from single and double rotors indicate a three-fold barrier height of 6.0 ± 1.5 kcal mol^?1. With this barrier height, the observed torsional displacement away from the COC equilibrium plane is found to be a significant feature of the model.     

Photo-dearomatization of n-methylphthalimides: an example of nucleophilic aromatic photoaddition of alcohol1,2

Dearomatization of N-methylphthalimide and its 3- and 4-methyl derivatives occurs upon irradiation of alcohol solutions. The X-ray crystal structure analysis of the product revealed the complete structure of a multi-substituted cyclohexene system. No evidence for formation of the photo-enol in the phthalimide system has been found during the study of the possible course of the photodearomatization. Unexpected deuterium incorporation at the N-methyl group is also reported.     

Suppression of the charge density waves in 1T-TaS2 by 70 MeV16O6+ bombardment

We report on the measurement of the nuclear quadrupole interaction by TDPAC on a single crystal of 1T-TaS₂ before and after bombardment with 70 MeV¹⁶O⁶⁺ ions. In 1T-TaS₂, two groups of inequivalent Ta-sites are observed at 298 K due to the presence of a nearly commensurate charge density wave (CDW) Upon¹⁶O⁶⁺ bombardment a single slightly broadened line is observed which resembles closely the incommensurate CDW state.     

Self-assembling, cystine-derived, fused nanotubes based on spirane architecture: design, synthesis, and crystal structure of cystinospiranes

A novel family of cystine-based spirobicyclic peptides (cystinospiranes) has been synthesized by a single-step procedure involving condensation of pentaerythritol-derived tetrachloride with either the simple L-cystine dimethyl ester or its C,C'-extended bispeptides leading to a variety of 19-membered spirobicyclic peptides or its N,N'-extended bispeptides affording the ring-expanded 25-membered cystinospiranes. The design is flexible with respect to the ring size that can be adjusted depending upon the length of the N,N'-extended cystine bispeptide, and the choice of an amino acid, as illustrated here with the preparation of a large number of cystinospiranes containing a wide variety of amino acids. X-ray crystal structure of the parent spirane (5a) revealed nanotube formation by vertical stacking of relatively flat spirobicyclic molecules through contiguous NH- - -O==C hydrogen bonding. The fused pair of parallel nanotubes is open-ended, hollow, and extends to infinity. Crystallographic parameters are the following: C(33)H(52)N(4)O(16)S(4), space group C2, a = 42.181(3) A, b = 5.1165(7) A, c = 11.8687(9) A, beta = 106.23(1) degrees.     

Use of the clark oxygen sensor with immobilized enzymes for determinations in flow systems

A small-volume cell has been constructed for amperometric flow measurements with a Clark oxygen sensor and its performance was tested. The Clark sensor can be combined with immobilized enzymes for determination of substances after enzymatic conversion during which oxygen is consumed or released. Two enzymes, glucose oxidase and tyrosinase, were used and two measuring techniques, employing the enzyme immobilized on the Clark sensor membrane and with the enzyme bound on a support in a preceding reactor, were tested and compared. It was found that, in the given system, measurement with the enzyme immobilized on the sensor membrane has better sensitivity, precision and response rate.     

In-beam magnetization measurements of thin Fe foils and simultaneous observation of the transient magnetic field at Pd ions

The well established phenomenon of heavy ion beam induced attenuations of transient magnetic fields (TF) was studied by measuring the in-beam magnetization of bombarded Fe foils employing the magneto-optical Kerr-effect. Whereas the macroscopic magnetization did not show any deterioration, the simultaneously measured TF of recoiling¹⁰⁸Pd(2⁺) ions was found to be substantially attenuated.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday