Structure of 6β-acetoxyprogesterone,C23H32O4

The X-ray crystal structure of 6-acetoxyprogesterone, C₂₃H₃₂O₄, has been determined. This compound crystallizes in space groupP2₁2₁2₁ witha=13.195(3),b=15.035(4),c=10.705(3) Å,V=2139.8(9) ų,M _r=372.5,Z=4,D _x=1.156g cm^–3; MoK radiation (=0.7107 Å),=0.72 cm^–1,F(000)=808;R=0.069, andR _w=0.052 for 1292 reflections. RingA adopts a normal 1,2-half-chair conformation. The side chain is typical for a 20-ketosteroid conformation.     

Structure of 17α-methyl-testosterone semihydrate,C20H30O2·1/2 H2O

The crystal structure of 17-methyltestosterone hemihydrate, C₂₀H₃₀O₂·1/2H₂O, has been determined:M _r =312.5, space groupP2₁2₁2₁2₁,a=6.374(2),b=12.807(2),c=43.398(5)Å,V _c =3543(2)ų,Z=8,D _x =1.172 mg^–3, CuK radiation ( = 1.54184 Å),(CuK)=5.5 cm^–1,F(000)=1376. The structure was solved usingMultan. The final conventionalR=0.053 (R _w =0.052) for 3634 reflections. The structure contains two crystallographically independent molecules in the asymmetric part of the unit cell that have almost identical geometry.     

Functionalization of Living Polymers via Ethoxysilane Based Compounds: Synthesis and Interaction with Silica Particles

To optimize the reaction of ω-carbanionic styrene or butadiene/styrene polymers with ethoxysilane based compounds, the influence of several experimental parameters on the orientation of the functionalization reaction and its yield was examined. The resulting end-functionalized polymers were systematically investigated by SEC, ¹H NMR and elementary analysis. The orientation of the reaction was found to be directly depending on the chemical nature of the chain end and / or on the type of additive (ethers, LiCl). Best results were obtained with tetraethoxysilane, provided the functionalization is conducted around 5°C, and the active chain end of isoprenyl type. These reactions were extended to bifunctional polymers, the reaction product of butyllithium with m-diisopropenylbenzene being used as an initiator. The efficiency of this initiator for the synthesis of well-defined bifunctionalized polydienes almost quantitatively fitted with three alkoxy functions at both chain ends was demonstrated. Some preliminary results on the mechanical properties of mixtures of functionalized polymers with silica were mentioned.     

Vibrational states of glassy and crystalline orthoterphenyl

Low-frequency vibrations of glassy and crystalline orthoterphenyl are studied by means of neutron scattering. Phonon dispersions are measured along the main axes of a single crystal, and the corresponding longitudinal and transversal sound velocities are obtained. For glassy and polycrystalline samples, a density of vibrational states is determined and cross-checked against other dynamic observables. In the crystal, low-lying zone-boundary modes lead to an excess over the Debye density of states. In the glass, the boson peak is located at even lower frequencies. With increasing temperature, both glass and crystal show anharmonicity. Received 7 December 1999     

Global Existence in Critical Spaces¶for Flows of Compressible¶Viscous and Heat-Conductive Gases

We are concerned with global existence and uniqueness of strong solutions for a general model of viscous and heat-conductive gases. The initial data are supposed to be close to a stable equilibrium with constant density and temperature. Using uniform estimates for the linearized system with a convection term, we get global well-posedness in a functional setting invariant with respect to the scaling of the associated equations (in space dimension N≧3). We also show a smoothing effect on the velocity and the temperature, and a decay on the difference between the density and the constant reference state. These results extend a previous paper devoted to the barotropic case (see [5]).     

Specific heat of the elpasolite Pb2MgWO6

The specific heat of Pb₂MgWO₆ has been measured in the temperature interval 83–370 K. An anomaly in the specific heat associated with the phase transition at T ₀=312.8K has been discovered. The thermodynamic parameters of the structural phase transition Fm3m-Pmcn have been determined. Fiz. Tverd. Tela (St. Petersburg) 41, 1686–1688 (September 1999)     

Calixarene-Based Copper(I) Complexes as Models for Monocopper Sites in Enzymes

A cavity that acts as a molecular funnel is formed from calix[6]arene 1 and [Cu^I(NCCH₃)₄]PF₆ [Eq. (a)]. An exchange of the well-protected acetonitrile ligand for other nitriles RCN is only possible with small R groups. The protection of the copper ions precludes oxidative dimerization; thus, the complexes mimic the mononuclear site of copper enzymes.     

Thermal conversion of 1-alkynyl-1,2-dihydrophosphetes into phosphinines

1-Alkynyl-1,2-dihydrophosphetes, as prepared by reaction of the appropriate titanacyclobutenes with alkynyldichlorophosphines, rearrange to the corresponding phosphinines via an original 4π-cycloreversion-6π-electrocyclization mechanism. The reaction of dimethyltitanocene with 1,4-diphenylbutadiyne affords a new 3-vinyltitanacyclobut-3-ene that can serve to prepare a 3-vinylphosphinine 6 by the same route. © 1996 John Wiley & Sons, Inc.