A variable concept for the preparation of branched glycosyl phosphatidyl inositol anchors

A variable concept for the synthesis of branched glycosyl phosphatidyl inositol (GPI) anchors was established. Its efficiency could be shown by the successful synthesis of the GPI anchor of rat brain Thy-1 and of the scrapie prion protein both in the water soluble 1c and lipidated form 1a. Retrosynthesis led to building blocks 2-6 of which 5 could be further disconnected to building blocks 7-9. Trichloroacetimidate 5 was built up in a straightforward manner starting from glycosyl acceptor 9 using known glycosyl donors 7 and 8. The carbohydrate backbone was then assembled by glycosylation of pseudodisaccharide acceptor 6 with donor 5. To ensure high stereoselectivity and good yields in the glycosylation reactions, anchimeric assistance was employed. Successive deprotection and introduction of the various phosphate residues gave the fully protected GPI anchors. Catalytic hydrogenation and acid-catalyzed cleavage of the Boc protecting groups afforded the target molecules, which could be fully structurally assigned.     

Absorption spectroscopic investigation of rhodamine dye vapors

The dyes rhodamine 6G and rhodamine 19 are investigated. The dye stability versus temperature and time is studied. Bulk dye stuff is found to be less stable than dye adsorbed to the stainless steel cell walls and in the vapor phase. Rhodamine 6G converts to rhodamine 19 before evaporation. Adsorbed rhodamine 19 and rhodamine 19 vapor disintegrate most likely into 2,7-dimethylrhodamine 110 at elevated temperatures (> 320°C). For rhodamine 19 vapor the absorption spectrum, the saturated vapor density and the latent heat of evaporation are determined. The vapor absorption spectra of rhodamine 19 and 2,7-dimethylrhodamine 110 are compared with solution spectra.     

Cyclisierungsreaktionen zu Pyrano[3,2-c]pyridinen und pyrano[3,2-c]chinolinen unter Verwendung von Ethoxymethylen-malodinitril bzw.-cyanessigester Synthesen mit Nitrilen, 50. Mitt. pyrano[3,2-c]quinolines with ethoxymethylene-malonitrile and-ethyl cyanoacetate,resp.

Reaction of ethoxymethylene-malonitrile and ethoxymethyleneethyl cyanoacetate, resp., with 4-hydroxy-2-pyridones (1a–b) and 4-hydroxy-2-quinolones (3a–b) leads to 2,5-dioxo-5,6-dihydro-2 H-pyrano[3,2-c]pyridine-(2a–d) and 2,5-dioxo-5,6-dihydro-pyrano[3.2-c]quinoline-derivatives (4a–d), resp.2a–d and4a–d exhibit remarkable visible fluorescence. Absorption- and emmission-data in different solvents are reported.     

Zur Verwendung von Quecksilber(I)-nitrat als reduktometrisches Reagens

Ohne ZusammenfassungVgl. diese Z. 137, 129 (1952/53); 138, 118 (1953)     

The isotopes259106,260106, and261106

In irradiations of²⁰⁷Pb and²⁰⁸Pb, respectively, with⁵⁴Cr theα-decay of the isotopes²⁵⁹106,²⁶⁰106, and²⁶¹106 could be observed for the first time. For²⁶⁰106 a spontaneous fission branch of (50 _?20 ⁺³⁰ )% was observed. The isotopes were identified by genetic relationships of α-decay after separation in-flight with the velocity filter SHIP and implantation into a position-sensitive silicon surface-barrier detector. The measured partial fission halflife of the doubly even isotope²⁶⁰106 of (7.2 _?2.7 ^+4.8 )ms exceeds the predicted values by at least a factor of 40. This result could be explained by the high shell corrections of the ground state mass, derived from the measured α-decay energies. The experimental results show evidence for an island of purely shell stabilized nuclei in the region of deformed isotopes beyond the actinides.     

Coherence effects in low energy Na*(3p)+Na+ scattering: Experiment and semiclassical calculations

Pronounced polarization effects have been observed in inelastic collisions of laser state-prepared Na^*(3p,M _L) with Na⁺ leading to Na^*(3d) for the energy rangeE _CM=20–45 eV. Using linearly polarized light the dependence of the inelastic process on the alignment of the electronic charge cloud of the Na^*(3p) prior to the collision has been measured. In studies with left and right hand circularly polarized light the angular momentum transferred in the collision process has been determined. The results are compared with similar data for the 3p→3s deexitation process studied previously [6]. The density matrix of the Na^*(3p) state has been evaluated with respect to the collisional excitation to Na^*(3d). Semiclassical calculations based on the coupled channel impact parameter approximation using pseudopotentials [7] and nonadiabatic rotational coupling elements for the Na ₂ ^* system [12] have been performed. The agreement with the experimental results is good, in particular for the higher collision energies.     

Poly[tris(diorganophosphinato)alanes]

Poly[tris(diorganophosphinato)alanes], [Al(OPRR′O)₃]_n, were synthesized in which the organic moieties (R,R′) contained from one to eighteen carbon atoms. Polymeric properties depended upon the organic moieties; polymers were fusible, tractable, and flexible when the organic moieties contained six or more carbon atoms. Soluble polymers were prepared by using mixtures of symmetrical and unsymmetrical phosphinates. One polymer, poly{bis[n-butyl(benzyl)phosphinato]di-n-octylphosphinatoalane}, exhibited a degree of polymerization greater than 1000 and an exceptionally high intrinsic viscosity of 37 dl/g. The properties of the different polymers are discussed, and feasible structures are proposed.