Rücktitelbild: C?H Activation Generates Period‐Shortening Molecules That Target Cryptochrome in the Mammalian Circadian Clock (Angew. Chem. 24/2015)

The synthesis and functional analysis of KL001 derivatives, which are modulators of the mammalian circadian clock, are described. By using cutting‐edge C H activation chemistry, a focused library of KL001 derivatives was rapidly constructed, which enabled the identification of the critical sites on KL001 derivatives that induce a rhythm‐changing activity along with the components that trigger opposite modes of action. The first period‐shortening molecules that target the cryptochrome (CRY) were thus discovered. Detailed studies on the effects of these compounds on CRY stability implicate the existence of an as yet undiscovered regulatory mechanism.     

Insight into the Mechanism of Hydrogenation of Amino Acids to Amino Alcohols Catalyzed by a Heterogeneous MoOx‐Modified Rh Catalyst

Hydrogenation of amino acids to amino alcohols is a promising utilization of natural amino acids. We found that MoO_x‐modified Rh/SiO₂ (Rh–MoO_x/SiO₂) is an efficient heterogeneous catalyst for the reaction at low temperature (323 K) and the addition of a small amount of MoO_x drastically increases the activity and selectivity. Here, we report the catalytic potential of Rh–MoO_x/SiO₂ and the results of kinetic and spectroscopic studies to elucidate the reaction mechanism of Rh–MoO_x/SiO₂ catalyzed hydrogenation of amino acids to amino alcohols. Rh–MoO_x/SiO₂ is superior to previously reported catalysts in terms of activity and substrate scope. This reaction proceeds by direct formation of an aldehyde intermediate from the carboxylic acid moiety, which is different from the reported reaction mechanism. This mechanism can be attributed to the reactive hydride species and substrate adsorption caused by MoO_x modification of Rh metal, which results in high activity, selectivity, and enantioselectivity.     

Iron‐Catalyzed Diboration and Carboboration of Alkynes

An iron‐catalyzed diboration reaction of alkynes with bis(pinacolato)diboron (B₂pin₂) and external borating agents (MeOB(OR)₂) affords diverse symmetrical or unsymmetrical cis‐1,2‐diborylalkenes. The simple protocol for the diboration reaction can be extended to the iron‐catalyzed carboboration of alkynes with primary and, unprecedentedly, secondary alkyl halides, affording various tetrasubstituted monoborylalkenes in a highly stereoselective manner. DFT calculations indicate that a boryliron intermediate adds across the triple bond of an alkyne to afford an alkenyliron intermediate, which can react with the external trapping agents, borates and alkyl halides. In situ trapping experiments support the intermediacy of the alkenyl iron species using radical probe stubstrates.     

Screening for Oral Cancer Using Electrochemical Telomerase Assay

Electrochemical telomerase assay (ECTA) developed by our group was evaluated in an oral cancer screening using exfoliated oral cells and tissues obtained from patients of oral cancer, mucosa associated disease, or healthy volunteers. Telomerase activity from ECTA is correlated with hTERT mRNA expression level using a real‐time PCR and was increasing in the following order: healthy volunteer group<mucosa associated disease group<oral cancer group. Sensitivity and specificity of ECTA were 88 % and 72 %, respectively when used 17 % of the threshold value based on the receiver operating characteristic curve in ECTA data.     

Contribution of Absorptive and Refractive Gratings to Mixed Holograms Using Xanthene-Dye-Doped Films

The contribution of absorptive and refractive gratings to a mixed hologram is investigated by means of two-wave coupling technique by moving a hologram. Polyvinyl alcohol films doped with xanthene-dyes such as erythrosin B,eosin Y, uranin and fluorescein which absorb an argon-ion laser light of 488 nm and 515 nm are used as hologram recording materials in our experiment. A simple model of the two-level one-step photo-bleaching well explains the growth of an absorptive grating and the refractive index and also the working wavelength dependence of growth of the refractive grating in the xanthene-dye-doped films.     

Revised structures of cymbopogone and cymbopogonol

The structures of cymbopogone and cymbopogonol were revised to D:A-friedo-18β,19αH-lupan-3-one and D:A-friedo-18β,19αH-lup-4(23)-en-3β-ol, respectively.