(20R,22R)-6α,7α-Epoxy-5α,27-dihydroxy-1-oxowitha-2,24-dienolide in Leaves of Withania somnifera: Isolation and its Crystal Structure

Abstract  (20R,22R)-6α,7α-Epoxy-5α,27-dihydroxy-1-oxowitha-2,24-dienolide (27-hydroxy-withanolide B) was isolated from Withania somnifera. The structure of the withanolide was established by spectral analysis and X-ray diffraction studies. The compound crystallizes in the orthorhombic space group P2₁2₁2₁ with unit cell parameters: a = 9.2163(3), b = 11.1828(4), c = 23.6146(9) ?, Z = 4. The crystal structure was refined to R = 0.0495 for 3,284 observed reflections. All the rings of the steroid skeleton are trans connected. Rings A and B exist in a half-chair conformation, ring C a chair, and five membered ring D is intermediate between a half-chair and an envelope. The δ-lactone ring E adopts a distorted sofa conformation. The twist along the length of the steroid nucleus is −6.5°. The characteristic pattern observed in the packing diagram is the appearance of twisted chains of molecules packed together to form layers. Index Abstract  Isolation and crystal structure analysis of (20R,22R)-6α,7α-epoxy-5α,27-dihydroxy-1-oxowitha-2,24-dienolide.      

Mössbauer study of CO-precipitated Fischer-Tropsch iron catalysts

Mössbauer spectroscopy studies of precipitated Fischer-Tropsch (FT) iron catalysts, viz. 100 Fe/5 Cu/4.2 K/x SiO₂, wherex=0,8, 16, 24, 25, 40, or 100, have shown that reduction of the oxide precursor in CO gives rise to -carbide Fe₅C₂ whose amount decreases with an increase of SiO₂ content. The -carbide is converted into magnetite Fe₃O₄ while catalyzing the FT synthesis reaction. A correlation between FT activity and the content of -carbide in the catalysts was found, which indicated that -carbide is active for FT synthesis reaction.     

Spectroscopic studies on Mn(II), Co(II), Ni(II), and Cu(II) complexes with N-donor tetradentate (N4) macrocyclic ligand derived from ethylcinnamate moiety

Manganese(II), cobalt(II), nickel(II), and copper(II) complexes are synthesized with a novel tetradentate ligand, viz. 1,5,9,13-tetraaza-6,14-dioxo-8,16-diphenylcyclohexadecane (L) and characterized by the elemental analysis, molar conductance measurements, magnetic susceptibility measurements, mass, 1H NMR, IR, electronic, and EPR spectral studies. The molar conductance measurements of the complexes in DMSO correspond to be nonelectrolyte nature for Mn(II), Co(II), and Cu(II) whereas 1:2 electrolytes for Ni(II) complexes. Thus, these complexes may be formulated as [M(L)X(2)] and [Ni(L)]X(2), respectively (where M = Mn(II), Co(II), and Cu(II) and X = Cl- and NO(3-)). On the basis of IR, electronic, and EPR spectral studies an octahedral geometry has been assigned for Mn(II) and Co(II) complexes, square-planar for Ni(II) whereas tetragonal for Cu(II) complexes. The ligand and its complexes were also evaluated against the growth of bacteria and pathogenic fungi in vitro.     

Design,synthesis and SAR of antitubercular benzylpiperazine ureas

Molecular Diversity - N-furfuryl piperazine ureas disclosed by scientists at GSK Tres Cantos were chosen as antimycobacterial hits from a phenotypic whole-cell screen. Bioisosteric replacement of...