Induced preference for axial chirality in a triarylmethylium o,o-dimer upon complexation with natural γ-cyclodextrin: strong ECD signaling and fixation of supramolecular chirality to molecular chirality

The ratio of the easily interconverting rotational isomers of biphenyl-2,2'-diylbis[bis(4-dimethylaminophenyl)methylium] (R)/(S)-1a(2+) can be biased to prefer an R configuration upon 1:1 complexation with γ-cyclodextrin in water. Through the reaction with Na(2)S, the preference of 1a(2+)@γ-CyD for an axial chirality of R can be fixed as the M-helicity of dihydrothiepin 2.     

Three New Glycosides from Viburnum plicatum Thunb. var. tomentosum Miq.

Three new glycosides, 7‐O‐tigloylsecologanol ( 1 ), 7‐O‐tigloylsecologanolic acid ( 2 ), and 3′‐O‐[(2S)‐2‐methylbutanoyl]henryoside ( 3 ), together with seven known ones, were isolated from the leaves of Viburnum plicatum Thunb . var. tomentosum Miq . Their structures were established on the basis of spectral and chemical data.     

Preparation of a fluorous protecting group and its application to the chemoenzymatic synthesis of sialidase inhibitor

2-(Perfluorohexyl)ethoxymethyl chloride was prepared as a novel fluorous protecting reagent. Neu5Ac aldolase-catalyzed chemoenzymatic transformation of N-acetyl-D-mannosamine to Neu5Ac derivatives was achieved successfully by using the fluorous reagent not only for hydroxy group protection but also for fluorous tagging. This chemoenzymatic method was applied to the synthesis of 2-deoxy-2,3-didehydrosialic acid 1 known as a potent sialidase inhibitor.     

Synthesis and optical properties of σ–π conjugated organic–inorganic hybrid gels

Organic–inorganic hybrid gels containing Si‐vinylene units have been synthesized by a hydrosilylation reaction of tri‐ or tetra‐ethynyl aryl compounds, 1,3,5‐triethynylbenzene (TEB), 3,3′,5,5′‐tetraethynylbiphenyl (TEBP), or tetrakis(4‐ethynylphenyl)methane (TEPM), and bisdimethylsilyl compounds, 1,1,3,3‐tetramethyldisiloxane (TMDS) or 1,4‐bisdimetylsilylbenzene (BDMSB), in toluene. Network structure of the resulting gels was quantitatively characterized by a scanning microscopic light scattering. The reactions yielded the gels having homogeneous network structure of 1.5–2.9 nm mesh size under the monomer concentrations that were relatively higher than the critical gelation concentration. The gels obtained from TEB showed broad absorption in the range from 340 to 370 nm, and emission in the range from 440 to 490 nm. The TEB–BDMSB gels showed remarkable red shift of the emission in comparison with that of the corresponding reaction solutions derived from the network formed by σ–π conjugation. The TEPM–TMDS, BDMSB gels exited by 280 nm showed not only the emission peak at around 360 nm derived from TEPM, but the broad peak at around 420 nm, which should be derived from interaction between phenyl groups of TEPM in the gels. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1360–1368     

Efficient waveguide-type four-color (red–green–blue–infrared) laser beam combiner for compact laser beam scanning image projectors

Optical Review - A waveguide-based combiner that can combine an infrared laser beam with primary color (red, green, and blue) laser beams is proposed and analyzed using a simulation based on the...     

Stereocontrolled Total Synthesis of Polygalolide A

The total synthesis of polygalolide A, a secondary metabolite that was isolated from a Chinese medicinal plant, is reported. A key issue in this synthesis was construction of an oxabicyclo[3.2.1] skeleton, which was solved by the development of an intramolecular Ferrier‐type C‐glycosylation of a glucal with siloxyfuran as an internal nucleophile. The substrate was prepared from D ‐glucal by the introduction of trimethylsilylacetylene and siloxyfuran groups. Although C‐glycosylation did not occur under the conditions found from model experiments, further examination revealed that the combination of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and 2,4,6‐collidine successfully afforded the desired product as a single diastereomer. The siloxy group at the C3 position played a crucial role in the stereocontrol of this reaction. The product was further transformed into a tetracyclic compound as follows: The vinyl ether and acetylenic moieties were reduced and the siloxy group was removed with a Barton–McCombie reaction. The construction of the six‐membered ether and the γ‐lactone provided the tetracyclic compound. Finally, a phenolic moiety was introduced by using a Mukaiyama aldol reaction to furnish polygalolide A.     

Optical transfer function analysis of Lau-Type grating atom interferometer

A grating interferometer composed of two transmission gratings in tandem irradiated incoherently was studied for an atom interferometer. Determination of its interference effect was made with consideration of the optical transfer function. An atom beam had a velocity distribution, which made the influence on the interference phenomenon. The calculated results show that the fringe (grating image) with relatively high contrast is obtained under a certain grating arrangement even if the interferometer is irradiated by a spatially incoherent polychromatic atom beam.     

Group Delay of a Coupled-Defect Waveguide in a Photonic Crystal

The group-delay characteristics of the light transmitting in a coupled defect waveguide (CDW) in a one-dimensional (1D) photonic crystal were experimentally investigated. Because of its simplicity, a 1D structure is suitable for scientific research as well as device application. The transmission spectrum agrees well with the calculated result by a characteristic matrix method. Group-delay measurement using the phase-shift method revealed the characteristic dispersion features and small group velocity of the CDW. This experimental investigation suggests that such unique features of the CDW promise the possibility of various applications such as a dispersion compensator.