Structural studies on a novel reaction product of malononitrile with aβb,δ-unsaturated allene aldehyde

Condensation of 2,5,5-trimethylhexa-2,3-dien-6-a1 with malononitrile affords an unexpected product, C₁₅H₁₆N_4X, ($\text{3}$), the structure of which was partially characterized by spectral (infrared, ultraviolet, ¹H, and ¹³C nmr) methods and fully elucidated by single crystal X-ray analysis. $\text{3}$ is l-cyano-2-amino-3-(2-propenyl)-5,5-dimethy-6- dicyanomethycycohexa-l,3-diene in a half-chair conformation. Conjugation of the $\text{cis}$-aminocyanoethenyl moiety leads to intermolecular

hydrogen bonding in the crystal. A reaction sequence and its mechanistic implications are proposed.     

Photo- and thermoinduced generation of 1,3-diaryl carbonyl ylides from 2,3-diaryloxiranes 1,3-dipolar cycloadditions to dipolarophiles

A group of symmetrically substituted 2,3-diaryloxiranes have been studied as photoprecursors for carbonyl ylides. The stereochemistry of the adducts obtained upon interception of these 4n pi-transient systems with a variety of dipolarophiles provides information on the mode(s) of electrocyclic opening of the oxiranes to carbonyl ylides, as well as the mechanism of the 4n + 2 cycloaddition process. The stereochemistry of the dipolarophiles is preserved in the cycloadducts, which is consistent with a concerted addition process; however, solvent effects, steric hindrance, and possibly secondary orbital overlap factors all may play a role in determining the product distribution.     

Characterization of Isomeric Cyclopentenone-Cycloheptene Photoadducts By 13C NMR Spectroscopy

The photochemistry of simple, alicyclic enones has been the subject of extensive study during the last decade, and this area is the subject of a recent review.² Investigation of the crossed-cycloaddition of cyclopentenone to a variety of alkenes was undertaken in our laboratory in connection with a program of synthesis of precursors for nonbenzenoid, aromatic systems. In a previous report³ we described the photoaddition of cyclopentenone to cycloheptene, from which four products were identified.     

Photoinduced cycloadditions of electron deficient nitrones to alkenes

Oxaziridines are proposed as intermediates in the photoinduced cycloadditions of electron deficient nitrones to dipolarophiles.     

Investigations of dehydroepiandrosterone. Part I: crystal structure of sublimed DHEA

The crystal structure of an orthorhombic polymorph of the title compound, crystallized by sublimation, has been determined. Dehydroepiandrosterone, C₁₉H₂₈O₂, space groupP2₁2₁2₁ witha=6.6408(4)b=11.4423(11)c=22.085(2)Å,V=1678.2(4)ų,Z=4. The structure was refined toR=0.051 for 2645 observed reflections. The conformation of the molecule is similar to that found in other polymorphs and solvates, with a chair A ring, an 8, 9 half-chair B ring, a chair C ring, and a 14 envelope D ring. Molecules are linked in chains by OH...O hydrogen bonds involving the carbonyl oxygen atom. The O...O distance is 2.855(3) Å, and the angle about H is 171(2)^o.     

新开花粉蛋白的盐酸胍去折叠过程

本文利用荧光光谱和园二色光谱了新开花粉蛋白的盐酸胍去折叠过程。结果显示：新开花粉蛋白的盐酸胍去折叠是一个只包含天然蛋白和变性终态的二态过程,与已经报道的天花粉蛋白的盐酸胍去折叠的过程不同。