A complex rotation : The solution conformation of spermidine (SPD) was elucidated by using diastereospecifically deuterated and 13C‐labeled derivatives to diagnose the orientation of seven conformationally relevant bonds. NMR coupling constants were determined for a complex formed from spermidine and adenosine triphosphate (ATP; see figure).
No bones about it : (?)‐Norzoanthamine, a promising candidate for an anti‐osteoporotic drug, was the target of a total synthesis (see scheme). The final bisaminal formation with AcOH/H2O gave the DEFG ring, while the cyclization precursor was prepared by installing the remaining bisaminal unit after oxidative cleavage of the cyclopentanol moiety.
The photochemical interconversion of the two allotropes of the hydrogen molecule [para-H(2) (pH(2)) and ortho-H(2) (oH(2))] incarcerated inside the fullerene C(70) (pH(2)@C(70) and oH(2)@C(70), respectively) is reported. Photoexcitation of H(2)@C(70) generates a fullerene triplet state that serves as a spin catalyst for pH(2)/oH(2) conversion. This method provides a means of changing the pH(2)/oH(2) ratio inside C(70) by simply irradiating H(2)@C(70) at different temperatures, since the equilibrium ratio is temperature-dependent and the electronic triplet state of the fullerene produced by absorption of the photon serves as an "on-off" spin catalyst. However, under comparable conditions, no photolytic pH(2)/oH(2) interconversion was observed for H(2)@C(60), which was rationalized by the significantly shorter triplet lifetime of H(2)@C(60) relative to H(2)@C(70). 相似文献
We calculated the Ti M2,3-VV Auger-photoelectron coincidence spectroscopy spectrum of TiO2(1 1 0) by a many-body theory. The spectral main line is governed by the DOS of the two O 2p holes living longer than the Ti ∣cd2L2〉 → ∣L2〉 super Coster-Kronig (sCK) decay. The two O 2p holes are created by the charge transfer core-hole screening at the Ti atomic site. Here c and L are the Ti 3p hole and the ligand O 2p hole, respectively. Analysis of the spectrum shows that the two (or three) CT O 2p holes in the π bonding states are localized, whereas those in the σ bonding states are delocalized. The three localized CT O 2p (π) holes in ∣cd3L3〉 in Ti M2,3 main line (or satellite) of TiO2(1 1 0) live longer than the Ti ∣cd3L3〉 → ∣d1L3〉 sCK decay so that the Coulomb repulsion from the surrounding Ti ions gives the O+ ion desorption from the surface. 相似文献
A resin-supported peptide catalyst effective for the asymmetric Michael addition of boronic acids to (E)-4-hydroxybut-2-enal was developed. From a spectral study, it was revealed that the optimum peptide consisted of both a β-turn and helix. Such a combination of secondary structures was essential for achieving a high catalytic ability. 相似文献
Al-planted MCM-41s (Al-M41s) with regular mesoporous structure and Si/Al ratio of 23-32 were successfully prepared by the template-ion exchange method in which the template/Si molar ratio and Si/Al ratio were adjusted at 1.44 and 5-15, and showed much higher catalytic activity for the titled reactions than the other types of Al-M41s prepared by post-synthesis or sol-gel methods. 相似文献
A phase transition between c(4x2) and 2x1 structures on the Si(001) surface has been observed at 200 K by low-energy electron diffraction. This transition is a second order order-disorder transition of the asymmetric dimer configuration. The streak pattern remains up to well above the transition temperature. The temperature dependence of the width and the length of the streak can be described in terms of the effects of a strong anisotropic coupling between adjacent asymmetric dimers. 相似文献