In situ catalyst improvement in the proline-mediated alpha-amination of aldehydes

Kinetic investigations show that the proline-mediated alpha-amination of aldehydes exhibits autoinductive rate behavior and amplification of product enantiomeric excess. Further experiments highlight the role of product, offering suggestions for the design of catalysts of improved efficiency for such transformations. The unusual characteristics exhibited by these reactions implicate amino acid catalysis in rationalizations of the origin of biological homochirality.     

Right-handed helical structure of expanded oligo(L-leucine) containing [Ru(terpyridine)2]2+ moieties

Expanded oligo(l-leucine)s, containing an alternate arrangement of a bis(terpyridine)ruthenium(II) moiety and a l-leucine residue, were synthesized and characterized by 1H NMR, UV, CD, and electrochemical properties. The intensity of CD spectra per ruthenium unit increased with the elongation of the peptide chain. 1H NMR analysis of a tetramer indicated the right-handed helical structure in acetonitrile.     

Chalcogenide-Lewis acid mediated reactions of electron-deficient alkynes with aldehydes

Reactions of but-3-yn-2-one (2) with aldehydes 1 in the presence of a Lewis acid and dimethyl sulfide (3 a) predominantly gave (E)-alpha-(halomethylene)aldols 4-5 in high yields, while reactions of methyl propiolate (6 a) mainly afforded (Z)-3-halogeno-2-(hydroxymethyl)acrylates 7-8 in low to moderate yields. A reaction of dimethyl acetylenedicarboxylate (10) with 1 a in the presence of TiCl(4) and 1,1,3,3-tetramethylthiourea (3 c) produced maleate (E)-11 (40 %) and butenolide 12 (40 %). When a reaction of 6 a with 1 a was carried out in the presence of TiBr(4) and 3 a (0.2 equiv) at -20 degrees C for 60 h, 3-(methylthio)-2-(hydroxyalkyl)acrylate 9 a was obtained in an 8 % yield. Experiments were conducted in order to elucidate the formation mechanism of 9 a, and it was made clear that 9 a was formed via the processes of the Michael addition of sulfide 3 a to alkynoate 6 a and an aldol reaction with 1 a and demethylation.     

Coumarin-4-ylmethoxycarbonyls as phototriggers for alcohols and phenols

Caged compounds can be used to regulate the spatial and temporal dynamics of signaling molecules in live cells. Photochemical properties of coumarin-4-ylmethoxy carbonates (1a-d) are investigated to construct caged compounds of hydroxy-containing molecules. All the compounds possess desired properties as phototriggers for alcohols and phenols. The 6-bromo-7-hydroxycoumarin-4-ylmethoxycarbonyl (Bhcmoc) group has the highest photochemical efficiency and is applied to make caged compounds of 1,2-dioctanoylglycerol (diC(8)), Tyr-OMe, and adenosine. [reaction: see text]     

Dioxacyclophanes as a Scaffold for Silicon-based Circularly Polarized Luminescent Materials

Planar chiral dioxacyclophanes were designed and synthesized as a key scaffold for materials with circularly polarized luminescence (CPL). Representative planar chiral 1,12-dioxa[12](1,4)naphthaleneophane-derived organosilane compounds (?)-(R)-1, (+)-(R)-2, and (?)-(R)-3 were prepared by (+)-sparteine-mediated aryl metalation and an electrophilic reaction with chlorosilanes. The absolute configurations of the planar chirality were determined in the R form by single-crystal X-ray analysis. Optically active compound (+)-(R)-2 exhibited blue fluorescence and a CPL signal with a dissymmetry factor (g_lum value) of 0.001 in solution. The electronic structure was corroborated by DFT and TD-DFT calculations rationalizing the observed spectroscopic properties.     

A kinetic study on Rh/binap-catalyzed 1,4-addition of phenylboronic acid to enones: negative nonlinear effect caused by predominant homochiral dimer contribution

A kinetic study on the Rh/binap-catalyzed 1,4-addition of phenylboronic acid using reaction calorimetry revealed that the catalytically inactive dimeric hydroxorhodium complex [Rh(OH)((R)-binap)]2 (RR-4) is the resting state. A negative NLE in eeprod and an amplified reaction rate were predicted and observed in the present reaction system characterized by the preferential formation of homochiral dimer.     

Development of a highly cardioselective ultra short-acting beta-blocker, ONO-1101.

A novel, highly cardioselective ultra short-acting beta-blocker, ONO-1101, has been developed for application in the emergency treatment of tachycardia and better control of heart rate in surgery. This agent is approximately nine times more potent in beta-blocking activity in vivo and eight times more cardioselective in vitro than esmolol. This beta-blocking drug has a short duration of activity, enabling rapid recovery after cessation of administration if side effects occur. It can be used safely in patients suffering from acute heart disease and represents a major therapeutic advance in the treatment of heart disease.