Large scale synthesis of bilirubin-XIIIα from IXα

A convenient large-scale preparation of bilirubin-XIIIα from IXα via acid-catalyzed isomerization is described.     

Photochemistry of 8,8,9,9-tetramethyl-1,3,4,6,7,8-hexahydro-1,4-ethanonaphthalene-2,5-dione,a δ-oxo-β,γ-unsaturated ketone

The oxa-di-π-methane rearrangement product 4,4,9,9-tetramethyltetracyclo [6.4.0.0^1,5.0^2,8]dodecane-7,12-dione ( 2 ) is formed selectively in a variety of solvents on either direct (λLD = 254, 300, 350 nm) or sensitized (xanthone, acetone, benzene) irradiation of the title compound 1 . The efficiency for this rearrangement is higher on S_o–S₁ excitation (Φ_?1 = 0.67) than on either S_o–S₂ or S_o–S₃ excitation (Φ_?1 = 0.58).     

Reactive polypeptides. II. Photochemistry of poly(γ-cinnamyl L-glutamate)

Poly(γ-cinnamyl L -glutamate) was irradiated in the presence and absence of benzophenone in dichloroethane. The irradiated polymers were analyzed by gas chromatography after hydrolysis. It was possible to assign the transformation in the presence of benzophenone to trans-cis photoisomerization by comparing the effects with those observed for a model compound cinnamyl acetate. The equilibrium composition of cis and trans isomers in the photostationary state was similar for the model compound and the polypeptide. Photoisomerization was found to be accompanied by marked side reactions for the direct irradiation. Circular dichroism spectra were empolyed to study the structure, and no changes in the structure were found for the irradiated polymers.     

γ,δ‐ and δ,ε‐Unsaturated Aldehydes from γ‐ and δ‐Lactones in One Step. Preliminary Communication

A one‐step transformation of γ‐ and δ‐(spiro)lactones into γ,δ‐ and δ,ε‐unsaturated aldehydes with an excess of formic acid in the vapor phase over a supported manganese catalyst is described for the first time. The scope and limitations of this new reaction are shown with different lactones as substrate, and a mechanistic rationale is proposed.     

Ni5‐δSn4Zn (δ ∼ 0.25) from single‐crystal data

Work on the ternary Ni–Sn–Zn phase diagram revealed the existence of the title compound pentanickel tetratin zinc, Ni_3.17Sn_2.67Zn_0.67 [Schmetterer et al. (2012). Intermetallics, doi:10.1016/j.intermet.2011.05.025]. It crystallizes in the Ni₅Ga₃Ge₂ structure type (orthorhombic, Cmcm) and is related to the InNi₂ type (hexagonal, P6₃/mmc) of the neighbouring Ni₃Sn₂ high‐temperature (HT) phase, but is not a superstructure. The crystal structure was determined using single‐crystal X‐ray diffraction. Its homogeneity range was characterized using electron microprobe analysis. Phase analysis at various temperatures indicated that the phase decomposes between 1073 and 1173 K, where a more extended ternary solid solution of the Ni₃Sn₂ HT phase was found instead.     

Photochemical reactions. 141st communication. Photochemistry of α,β-unsaturated δ,ϵ-epoxyketones of the ionone series

On n,π*- as well as on π,π*-excitation, the 4,5-epoxy-α-ionones (E)- 1 , (E)- 2 , and (E)- 3 undergo (E)/(Z)-isomerization and subsequent γ-H-abstraction leading to the corresponding 4-hydroxy-β-ionones (E/Z)- 9 , (E/Z)- 13 , and (E/Z)- 17 as primary photoproducts. On photolysis of (E)- 3 , as an additional primary photoproduct, the β,γ-unsaturated σ,?-epoxy ketone 18 was obtained. The other isolated compounds, namely the 2H-pyrans 10A + B and 14A + B as well as the retro γ-ionones 11 and 15A + B , represent known types of products, which are derived from the 4-hydroxy-β-ionones (E/Z)- 9 and (E/Z)- 13 , respectively.     

β‐LiMoO2(AsO4)

A new non‐centrosymmetrical form of lithium molybdyl arsenate has been synthesized and grown as a single crystal. The structure of β‐LiMoO₂(AsO₄) is built up of corner‐sharing AsO₄ tetrahedra and MoO₆ octahedra which form a three‐dimensional framework containing tunnels running along the a axis, wherein the Li⁺ cations are located. This novel structure is compared with the compound LiMoO₂(AsO₄) of the same formula, and with those of AMO₂(XO₄) (A is Na, K, Rb or Pb, M is Mo or V, and X is P or As) and B(MoO₂)₂(XO₄)₂ (B is Ba, Pb or Sr).     

Structure and Properties of γ‐Brass‐Type Pt2Zn11—δ (0.2 < δ < 0.3)

The γ‐brass type phase Pt₂Zn_11—δ (0.2 < δ < 0.3) was prepared by reaction of the elements in evacuated silica ampoules. The structures of crystals grown in the presence of excess zinc or alternatively excess platinum were determined from single crystal X‐ray diffraction intensities and confirmed by Rietveld profile fits. Pt₂Zn_10.72(1) crystallizes in the space group I4¯3m, a = 908.55(4) pm, Z = 4. The structure refinement converged at R_F = 0.0302 for I_o > 2σ (I_o) for 293 symmetrically independent intensi ties and 19 variables. The structure consists of a 26 atom cluster which is comprised of four crystallographically distinct atoms. The atoms Zn(1), Pt(1), Zn(2) and Zn(3) form an inner tetrahedron IT, an outer tetrahedron OT, an octahedron OH, and a distorted cuboctahedron CO respectively. About 14 % of the Zn(1) sites are unoccupied. Pt₂Zn_10.73 melts at 1136(2) K. It is a moderate metallic conductor (ρ₂₉₈ = 0.2—0.9 mΩ cm) whose magnetic properties (χ_mol = —4.6 10^—10 to —5.4 10^—10 m³ mol^—1) are dominated by the core diamagnetism of its components.     

Thiocyanate-assisted demetallation of α,β,γ,δ-tetra(p-sulfophenyl)porphinatoindium(III) in aqueous media

The rate law for the demetallation of the title indium(III)-porphin complex in aqueous acidic thiocyanate media at 3.00M ionic strength was found to be of the form where [H₄P^2?] is the concentration of the diacid product formed, [InP]_t is the total concentration of all forms of indium(III)-porphin complex present, and a and b are constants. The constant a is a pseudo-third-order rate constant with the value (0.057 ± 0.005)M^?2 s^?1 and b has the value 0.704M^?2 at 50.5°C. If the mechanism for demetallation involves ringpuckering with the attachment of two H⁺ ions, then 1/b can be identified with the product K₁K₂ for the stepwise dissociation of two protons from two ring pyrrolic nitrogen atoms of H₂InP^?. In the sulfonated tetraphenylporphin used for these studies the ring pyrrolic nitrogen atoms seem to be the most probable sites for protonation. If this identification is correct, the value of 1.42 ± 0.13 found for the product K₁K₂ shows the enormous effect that the presence of the In³⁺ center has on the ionization constants of these two protons. That the kinetic studies show saturation effects with respect to proton addition to InP^3? may result from the fact that In³⁺ sits about 0.6 Å above the porphin ring.     

PHYTOCHROME MODELS,PART 9. CONFORMATION SELECTIVITY OF THE PHOTOCYCLIZATION OF THE BILIVERDIN IX γ and IX δ DIMETHYL ESTERS*

Abstract— The photocyclization of the biliverdin IX γ and IX δ dimethyl esters to phorcabilin and neobiliverdin IX δ dimethyl ester, respectively, markedly depends on the irradiation wavelength within the first electronic absorption band. The quantum yields of reaction are highest on irradiation at575–600 nm. As judged from fluorescence excitation studies, absorption by the stretched conformations of the biliverdins is relatively important at these wavelengths. At longer wavelengths, where the reaction efficiency sharply declines, absorption by the coiled form predominates. Based on these findings and on supporting evidence from the solvent and temperature influence on the reaction, the photocyclization is proposed to occur selectively from a stretched conformation (an example of the principle of nonequilibration of excited rotamers), competing with E-Z isomerization of the centralC–10 double bond. A kinetic hydrogen isotope effect on the photochemical reaction rate of N,N,N-trideuteriated biliverdin IX δ dimethyl ester indicates that the primary photoproduct in the cyclization reaction is labile and reacts via two competing processes: reopening to the starting material and a solvent-mediated proton shift. The latter process leads to the phorcabilin and neobiliverdin IX δ esters. The results suggest, as a general rule, that the stretching of coiled biliverdins is confined to thermal and photochemical transformations within the B/C partial structure, while the Z-syn geometry of the A/B and C/D moieties is retained.