Iridium complex-catalyzed highly enantio- and diastereoselective [2+2+2] cycloaddition for the synthesis of axially chiral teraryl compounds

An asymmetric [2+2+2] cycloaddition of an alpha,omega-diyne, possessing ortho-substituted aryl groups on its terminus, and a monoalkyne with oxygen functionalities gave various axially chiral teraryl compounds. The coupling proceeded with extremely high enantio- (>99.5% ee) and diastereoselectivities (dl/meso = >95/5) when catalyzed by an iridium-chiral phosphine complex. As the products were readily transformed into diol compounds by deprotection without racemization, the present procedure provides access to a new chiral pool of diol compounds with C2 symmetry.     

Hydrophobic scale: a second parameter to elucidating various specific ligand-protein interactions

In the sequence Fourier analysis (SFA) of specific interactions such as those between fibroblast growth factors (FGFs)/FGF receptors (FGFRs), bone morphogenetic proteins (BMPs)/BMP receptors (BMPRs), or tumor repressor protein p53/mouse double minute 2 homolog (MDM2), the characteristic frequency peak(s) could be observed with the hydrophobic scale for 20 amino acids as well as 4 nucleotides as the physicochemical parameter, but not successfully with the absolute electronegativity scale. This result implies that these two independent scales should be appropriately selected in various specific ligand-protein interactions, though the critical difference has to be determined.     

A series of trinuclear Cu(II)Ln(III)Cu(II) complexes derived from 2,6-Di(acetoacetyl)pyridine: synthesis, structure, and magnetism

A series of trinuclear Cu(II)Ln(III)Cu(II) complexes with the bridging ligand 2,6-di(acetoacetyl)pyridine have been prepared by one-pot reaction with Cu(NO(3))(2).3H(2)O and Ln(NO(3))(3).nH(2)O in methanol. X-ray crystallographic studies for all the complexes indicate that two L(2)(-) ligands selectively sandwich two Cu(II) ions with the 1,3-diketonate entities and one Ln(III) ion with the 2,6-acetylpyridine entity to form a trinuclear CuLnCu core bridged by the enolate oxygen atoms. Cryomagnetic properties of the complexes are studied with respect to the electronic structure of the Ln ion.     

Tin(IV) chloride-chiral pyrogallol derivatives as new Lewis acid-assisted chiral Brønsted acids for enantioselective polyene cyclization

[reaction: see text] New Lewis acid-assisted Br?nsted acids (LBAs), tin(IV) chloride-2,6-dialkoxyphenols, serve as artificial cyclases for biomimetic polyene cyclization. For example, the enantioselective cyclization of 4-(homogeranyl)toluene using tin(IV) chloride-2,6-di[(1'R,2'R)-trans-2'-(3' ',5' '-xylyl)cyclohexanoxy]phenol gave a trans-fused tricyclic compound with 85% ee.     

Novel stereoselective entry to 2'-beta-carbon-substituted 2'-deoxy-4'-thionucleosides from 4-thiofuranoid glycals

2'-Beta-methyl- and 2'-beta-hydroxymethyl-2'-deoxy-4'-thionucleosides have been synthesized through PhSeCl-mediated electrophilic glycosidation using 4-thiofuranoid glycals having carbon substituents at the C2-position as a glycosyl donor. Preparation of these glycals were carried out by means of the C2 lithiation of 1-chloro-4-thiofuranoid glycal with LTMP followed by the Birch reduction of the chlorine atom. [reaction: see text]     

On the Fourier coefficients of Hilbert-Maass wave forms of half integral weight over arbitrary algebraic number fields

The purpose of this paper is to derive a generalization of Shimura's results concerning Fourier coefficients of Hilbert modular forms of half integral weight over total real number fields in the case of Hilbert-Maass wave forms over algebraic number fields by following the Shimura's method. Employing theta functions, we shall construct the Shimura correspondence Ψ_τ from Hilbert-Maass wave forms f of half integral weight over algebraic number fields to Hilbert-Maass wave forms of integral weight over algebraic number fields. We shall determine explicitly the Fourier coefficients of in terms of these f. Moreover, under some assumptions about f concerning the multiplicity one theorem with respect to Hecke operators, we shall establish an explicit connection between the square of Fourier coefficients of f and the central value of quadratic twisted L-series associated with the image of f.     

Monitoring molecular beacon DNA probe hybridization at the single-molecule level

We have monitored the reaction dynamics of the DNA hybridization process on a liquid/solid interface at the single-molecule level by using a hairpin-type molecular beacon DNA probe. Fluorescence images of single DNA probes were recorded by using total internal reflection fluorescence microscopy. The fluorescence signal of single DNA probes during the hybridization to individual complementary DNA probes was monitored over time. Among 400 molecular beacon DNA probes that we tracked, 349 molecular beacons (87.5 %) were hybridized quickly and showed an abrupt fluorescence increase, while 51 probes (12.5 %) reacted slowly, resulting in a gradual fluorescence increase. This ratio stayed about the same when varying the concentrations of cDNA in MB hybridization on the liquid/surface interface. Statistical data of the 51 single-molecule hybridization images showed that there was a multistep hybridization process. Our results also showed that photostability for the dye molecules associated with the double-stranded hybrids was better than that for those with the single-stranded molecular beacon DNA probes. Our results demonstrate the ability to obtain a better understanding of DNA hybridization processes using single-molecule techniques, which will improve biosensor and biochip development where surface-immobilized molecular beacon DNA probes provide unique advantages in signal transduction.     

Selective cross-catenation of Pd(II) and Pt(II) coordination rings

The reversible cross-catenation of two different coordination rings (Pd(II)- and Pt(II)-linked rings) has been achieved by using the labile nature of the Pd-N interaction and efficient hydrophobic contact between the rings.