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Chiral dopants with a spiro structure for nematic liquid crystals were synthesized from optically active 3,3′-(4H,4′H)-spirobi(2H-naphtho[1,2-b]pyran)-6,6′-dicarboxylic acid, and their helical twisting power (HTP) values were evaluated. Chiral dopants having the S configuration induced minus helices in the host nematic liquid crystals. It was found that the novel ester-linked spiro chiral dopants exhibited large molar HTP values. In particular, a chiral dopant with two pyrimidine structures in the side chain moiety showed the highest molar HTP value of 62.1 µm−1mol−1kg. In contrast, ether-linked chiral dopants showed relatively small molar HTP values.

To enhance biological activities on the basis of the sugar cluster effect, a series of carbosilane dendrimers as core scaffolds for the construction of glycodendrimers was systematically synthesized from appropriate chlorosilanes by a combination of alkenylation and hydrosylation reactions. Those carbosilane dendrimers having terminal CC double bonds underwent general hydroboration reactions to give corresponding primary polyols. Further transformations of the alcohols were then performed by mesylation followed by a displacement with NaBr to provide corresponding dendrimers with 4 to 36 bromine atoms at each terminal end. Assembly of trisaccharide moieties of globotriaosyl ceramide using alkyl halide-type carbosilane dendrimers as the core frame was conducted in liquid ammonia by a one-pot reaction involving selective removal of a benzyl group under the Birch reduction condition and subsequent SN2 reaction to yield a series of carbosilane dendrimers having appropriate numbers of trisaccharide moieties. These dendrimers have unique shapes and adequate numbers of terminal trisaccharide moieties. Some of the dendrimers showed unique biological activity against Stxs, which were produced by pathogenic Escherichia coliO157:H7.

As an application of a one-pot reaction involving Birch reduction and subsequent SN2 reaction in liquid ammonia, synthetic assembly of trisaccharidic moieties of globotriaosyl ceramide onto carbosilane dendrimers was accomplished using tris(3-bromopropyl)phenylsilane and tristris(3-bromopropyl)silylpropylphenylsilane as the core scaffolds. The common globotriaosyl derivative having benzylsulfide functionality at the terminal of the aglycon was efficiently prepared from d-galactose and d-lactose as starting materials. The glycosyl donor derived from galactose and the glycosyl acceptor derived from lactose were condensed in the presence of silver triflate as the best promoter to provide corresponding trisaccharide with newly formed -1−4 linkages in 90% yield. Fully benzylated protection of the trisaccharide was deprotected under the Birch reduction condition followed by acetylation to give an acetate in which alkene was converted into benzyl sulfide by radical addition of -toluenethiol in high yields. On the other hand, carbosilane dendrimers were prepared from appropriate chlorosilanes as starting materials by a combination of hydrosylation followed by alkenylation. The terminal CC double bonds of the carbosilanes were converted into corresponding alcohols by means of the usual hydroboration reaction, and the alcohols underwent further chemical manipulation to give carbosilane dendrimers with peripheral bromine atoms.

We previously developed linear polymers bearing clustered trisaccharides of globotriaosylceramide (Gb3) as orally applicable Shiga toxin (Stx) neutralizers. Here, using a Gb3 polymer with a short spacer tethering the trisaccharide to the core, we found that shortening the spacer length markedly reduced the binding affinity for Stx2 but not Stx1. Moreover, mutational analysis revealed that the essential binding sites of the terminal trisaccharides were completely different between Stx1 and Stx2. These results provide the molecular basis for the interaction between Stx B subunits and Gb3 polymers.

The preparation and characterization of new amphiphilic polysilanes containing chiral pendant ammonium groups are described. Polyalkylphenylsilanes (alkyl; C1—C8) (I) were prepared, and the Friedel—Crafts reaction of I was carried out to give p-chloromethylated polysilanes (II). II were treated with optically active amines such as N,N-dimethyl-a-methylbenzylamine (1), N,N-dimethylphenylalaninol (2), N,N-dimethyl-O-acethylphenylalaninol (3), N,N-dimethyl-iso-leucinol (4), N,N-dimethylleucinol (5) and N,N-dimethyl-1-phenylethanol (6) to give the corresponding amphiphilic polysilanes bearing chiral pendant ammonium moieties. All polymers prepared were soluble in water, ethanol and acetonitrile. The circular dichromic spectra (CD) of the polymers in ethanol showed that the polymer had a screw-sense main chain.

With interest in clustering bioactive chitooligosaccharides, a pair of amphiphilic derivatives of around DP (degree of polymerization) 6, which has been considered to be the minimum molecular length for some kinds of bioactivity, was synthesized. Homologous derivatives of chitopentaose and chitoheptaose carrying tetradecanoyl and tetradecyloxy groups at the NH and C-1 of the reducing ends, respectively, were actually obtained using a 1,6-anhydro-2-azido-2-deoxy-ß-D-glucopyranose derivative as the terminal precursor and a chitobiose derivative as the elongation unit. Micelle formation of both derivatives was assumed from the results obtained by dye solubilization tests.

As a novel type of artificial receptor for Vero toxins, three pairs of carbosilane dendrimers uniformly carrying 12, 6, and 3 units of trisaccharide moieties of globotriaosyl ceramide were prepared through formation of the sulfide linkages in liquid NH 3, which revealed unexpected differences among their biological responses.

A series of new carbosilane dendrimers carrying cyanobiphenyl derivatives was prepared starting from the tertiary core molecule, triallylphenylsilane. The phase transition of the dendrimers depends on the dendrimer generation, and the spacer lengths were investigated by using differential scanning calorimetry (DSC) and an optical polarizing microscope. All of the dendrimers prepared exhibited smectic A phases. The phase behavior on the phase-transition pattern of the DSC curve and the texture appearances of G2-mesogen(5) carrying twenty-seven mesogens were observed to be similar to that of the reported G2 dendrimer prepared starting from the quarternary core molecule, tetraallylsilane, carrying thirty-six mesogens.

As a basic model reaction for assembling specific functional carbohydrate molecules on a novel core substance by making covalent bonds, an efficient one-pot reaction involving Birch reduction and a subsequent SN2 replacement was developed, employing trivalent and tetravalent carbosilane bromides as the core and monodeoxy-monomercapto-ß-cyclodextrin as the functional carbohydrate. It was confirmed that carbosilane derivatives containing a suitable spacer molecule were of wide applicability as a new core substance for the construction of diverse functional materials.

For the preparation of l-iduronic acid, trehalose was converted into a derivative of a novel disaccharide, β- l-idopyranosyl β- l-idopyranoside, through diastereoselective hydroboration of the 5, 5′-di-eno intermediate. The 6- and 6′-hydroxy groups were then oxidized in two steps to give a disaccharide composed of 2 units of l-iduronate moieties, which underwent acidic cleavage of the glycosidic bond to give the target compound.

A pair of disaccharidic glycals thoroughly O-benzylated except the 4′- or the 6′-hydroxyl groups were prepared as the monomers for iodonium ion-promoted polymerization, which proceeded under dark conditions to give polysaccharides of more than DP 12 (24 saccharide). Reductive removal of the iodine atom and subsequent deprotection gave polysaccharides alternatively composed of β- d-glucopyranosyl and 2-deoxy-α, β- d-glucopyranosyl residues.

With interest in clustering of bioactive chitooligosaccharides of more than dp 6, a chitoheptaose derivative 1carrying tetradecanoyl and tetradecyloxy groups at the NH and the C-1 of the reducing end, was prepared. The hydrophobic groups were introduced step by step after completion of the heptasaccharide skeleton using a chitobiose derivative as the elongation unit. Micelle formation of 1in water was confirmed by dye solubilization check. © 1997 Elsevier Science Ltd.

In the course of our studies on the synthesis of amphiphilic chitoheptaose derivatives carrying binary long hydrocarbon chains at the reducing sugar, tetradecyl 4-O-(2-amino-2-deoxy-β-D-glucopyranosyl)-2-deoxy-2-tetradecanamido-β-D-glucopyranoside was prepared as a model. For general applicability, the 1,6-anhydro-2-deoxy-2-tetradecanamido-β-D-glucopyranosyl moiety was employed as a precursor of the reducing end. Acetolysis of the 1,6-anhydro ring using triethylsilyl triflate gave an oxazoline intermediate as a major product, accompanied by α-glycosyl acetate as a by-product. Immediate treatment of the mixture with 1-tetradecanol and protic acid followed by a separation work-up efficiently led to tetradecyl β-glycoside derivative.

Triorganosilylmethylanimes, Me(PhCH2)RSiCH2NH2[R=C6H5(Ia), p-MeC6H4(Ib), m-MeC6H4(Ic), and o-MeC6H4(Id)] were resolved by fractional crystallization of the (+)-tartaric acid salts of the racemic triorganosilylmethylamines from methanol. The following optically active amines were obtained from the less soluble diastereoisomers; (+)-Ia([α]D21+9.9 (c=5, in Et2O)), (−)-Ib ([α]D21−16.6 (c=5, in Et2O)), (+)-Ic([α]D22+11.1 (c=5, in Et2O)), and (+)-Id ([α]D21+7.0 (c=5, in Et2O)).

The reactions of N-(germylmethyl)benzylamine derivatives with butyllithium were carried out. Facile cleavages of Ge–C bonds of the N-benzylgermylmethylamine derivatives giving the corresponding germyl anions and N-pentylbenzylamine were observed. The reaction mechanism of the Ge–C bond cleavage was discussed.

Optically active α-amino organosilanes such as benzylmethyl(o- or p-tolyl)silylmethylamine were converted into benzylmethylphenyl(o- or p-tolyl)silane, of which the configurations had been known. From these observations, it was found that (+)- and (−)-benzylmethyl(o- or p-tolyl)silylmethylamine has Sand Rconfiguration respectively. Furthermore, the stereochemistry of the reaction of benzylmethyl(methoxy)phenylsilane with some organometallic agents was investigated.

A facile cleavage reaction of the germanium–carbon bond of (germylmethyl)amine derivatives to give a germyl anion and an azomethine derivative was developed. The effects of substituents such as phenyl, benzyl, and ethyl groups on the germanium and nitrogen atoms of the (germylmethyl)amine derivatives on the cleavage reaction, were investigated. The mechanism was also investigated based on the stereochemistry of the cleavage reaction using an optically active organogermanium compound.

Reduction of the 7-silanorbornene derivatives obtained from Diels–Alder reactions of 1,1,3,4-tetramethylsilacyclopenta-2,4-diene (1a), and 2,3-dimethyl-5-silaspiro[4.4]nona-1,3-diene (1b) with maleic anhydride was carried out by lithium aluminum hydride (LAH) to give diol derivatives. Attempts to substitute the hydroxyl groups with chlorine using various chlorination agents such as thionyl chloride and triphenylphosphine in carbon tetrachloride were unsuccessful. The latter reaction, however, gave a corresponding ether derivative as a result of intramolecular cyclization. Reactions of the 7-silanorbornene derivatives with some nucleophiles such as LAH, (n-Bu)4NF, n-BuLi, and PhLi were also investigated.

The in situreaction of dialkoxydichlorosilanes, such as dimethoxy-, diethoxy-, dipropoxy-, dibutoxy-, and diisobutoxydichlorosilane, with isoprene and magnesium in tetrahydrofuran (THF) was investigated. It was found that the double annelation product, i.e., 2,7-dimethyl-5-silaspiro[4.4]nona-2,7-diene (1), was obtained from diethoxy-, dipropoxy-, and dibutoxydichlorosilane in 87.0, 65.2, and 66.5% yields respectively. On the other hand, the reaction of dimethoxy- and diethoxydichlorosilane with butadiene and magnesium in THF gave 5-silaspiro[4.4]nona-2,7-diene (7) in 20.7 and 35.4% yields respectively. Several silaspirononane derivatives were synthesized from 1.

New optically active a-amino organosilanes, such as benzylmethylphenylsilylmethylamine, benzylmethyltolylsilylmethylamines, and anisylbenzylmethylsilylmethylamines, were obtained by the fractional crystallization of the salts of the amines and (+)-tartaric acid. Benzylmethylphenylsilylmethylamine was converted into benzylmethyl-1-naphthylphenylsilane, of which the configuration had been known. From these observations, it was found that benzylmethylphenylsilylmethylamine, benzylmethylphenylsilane, and benzylmethoxymethylphenylsilane had S(+), S(-), and S(+) configurations respectively.

New optically active organosilicon compounds such as (benzylmethylphenylsilyl)acetic acid (1) and (ethylmethylphenylsilyl)acetic acid (2) were synthesized. Application of these acids as the optical purity determining agents for chiral amines and alcohols were successfully carried out. In addition, it was also revealed that optically active (benzylmethylphenylsilyl)methylamine (3) and [benzylmethyl(o-tolyl)silyl]methylamine (4) are able to be used as the optical purity determining agents for chiral carboxylic acids.

The polymerization of 1,1,3-trimethyl-1-silacyclopentene-3 (I), 1-methyl-, 1-allyl-1,1-diallyl-1-silacyclopentenes and -pentanes with aluminum chloride was carried out. By means of an IR spectroscopic analysis of the resulting polymers, it was established that not only ring opening but also vinyl polymerization due to the C–C double bond occur in this polymerization. Attempts to polymerize I with other catalysts, such as BF3·OEt2, AIBN, KOH, and a Ziegler catalyst, were unsuccessful.

We observed an electroluminescence (EL) of poly bis(p-propoxyphenyl)silane (PBPPS) from a double-layer device with an electron transport layer of 8-hydroxyquinoline aluminum (Alq3) for the first time. The EL spectrum at 77 K consisted of a PBPPS emission at 3.0 eV, which coincided with the photoluminescence spectrum, and a broad emission band between 1.8 and 2.7 eV.

Reaction of silole derivatives such as 1,1,3,4-tetramethylsilole (1)1)and 2,3-dimethyl-5-silaspiro[4.4]nona-1,3-diene (2) with dimethyl acetylenedicarboxylate (DMADC) were investigated. It was found that the reactions of 1and 2with DMADC in toluene gave 7-membered ring compounds; trimethyl 7-methoxy-3,3,3′,4′-tetramethyl-6-oxa-3-sila-1,2-benzocyclohepta-1,4-diene-4,5,6′-tricarboxylate and trimethyl 5-methoxy- 8,9-dimethylspiro[5H-4,1-benzoxasilepin-1,1′-silacyclopentane]-2,3,6-tricarboxylate, respectively.

New chiral dopants for nematic liquid crystals, containing a (S)-3,3′-(4H,4′H)-spirobi(2H-naphtho[1,2-b]pyran) skeleton, were synthesized and their helical twisting powers (HTP) were evaluated. A chiral dopant with two terphenyl structures showed the highest molar HTP value of 50.3 μm−1mol−1kg.

The synthesis and optical resolution of 3,3′-(4H,4′H)-spirobi(2H-naphtho[1,2-b]pyran)-6,6′-dicarboxylic acid were successfully accomplished. The formation of the spiro skeleton and the bromination of the aromatic ring were easily achieved in the presence of bromine. Optical resolution was achieved by amidation with l-valinol (2-amino-3-methyl-1-butanol).

A series of new carbosilane dendrimers carrying a mesogenic group, 5-((+)-2-fluorooctyloxy)-2-phenylpyrimidine derivative, were prepared successfully. Although the dendrimers did not show any clear Sc*phases, it was found that all the dendrimers prepared were operative as chiral dopants.

A new silaspiro compound, i.e., spiro[silacyclobutane-1,9′-[9H-9]silafluorene](1) was synthesized in 75% yield. It was found that the pyrolysis of 1at 650°C under a reduced pressure gave a head-to-tail silaethene dimer in 15% yield. Copyrolysis of 1in the presence of benzophenone gave 1,1-diphenylethene and a siloxane oligomer in 50 and 30% yield, respectively.

The synthesis and characterization of new amphiphilic polysilanes containing chiral pendant ammonium groups are described. Chloromethylation of polyhexylphenylsilane (PHPS) was carried out to give p-chloromethylated PHPS (1). 1 was treated with optically active N,N-dimethyl-α-methylbenzylamine to give an amphiphilic polysilane. The polymer prepared was soluble in water, ethanol and acetonitrile. The circular dichromic spectrum of the polymer in ethanol showed that the the polymer had a screw-sense main chain.

A series of new carbosilane dendrimers was prepared by repeating a combination of hydrosilation and allylation on a core molecule, triallylphenylsilane. Subsequent hydroboration and oxidation of the dendrimers gave the polyol derivatives, which were treated with a mesogenic molecule, 6-(4-cyanobiphenyl-4′-oxy) hexanoyl chloride, to give new carbosilane dendrimers carrying mesogenic groups. It was found that the all carbosilane dendrimers exhibited liquid crystal phases. The effects of the dendrimer generations on the ranges of liquid crystal temperature were investigated.

Dichlorodiethoxysilane was treated with isoprene in the presence of magnesium in THF. It was found that new silacyclopentene derivatives i.e., 1,1-diethoxy-3-methyl-1-silacyclopentene-3(1), and 2,7-dimethyl-5-silaspiro[4.4]nonadiene-2,7(2), were produced in good yields, while sodium was used instead of magnesium in the reaction 2was obtained in a low yield.

New optically active organogermanium compounds, such as [methylphenyl(o-tolyl)-, benzylmethylphenyl-, benzylmethyl(o-tolyl)-, and benzyl(o-methoxyphenyl)methylgermyl]methylamine, were prepared in high optical purity.

(±)-a-Ethylbenzylamine ((±)-1) was efficiently resolved into a pair of enantiomers by fractional crystallization as its cis-2-benzamidocyclohexanecarboxylic acid (2) salt. Moreover, it was found that each of both enantiomers was obtained by mutual resolution between (±)-1and (±)-2. The optically active amine (1) was substantially capable of resolving a variety of chiral carboxylic acids.

Application of optically active carbonfunctional organosilanes for the determination agent of optical purities of chiral amines, alcohols, and carboxylic acids by using NMR spectrometer were investigated.

A new silaspiro compound, i.e., 2,6-dimethyl-4-silaspiro[3.4]oct-6-ene, was synthesized by treating 1,1-dichloro-3-methyl-1-silacyclobutane with isoprene in the presence of magnesium in tetrahydrofuran. The reactions of the silaspiro compound with LiAlH4, H2PtCl6, dimethyl acetylenedicarboxylate in the presence of PdCl2(PPh3)2, and the Simmons-Smith agent were investigated.

Poly[9,9-dioctylfluorenyl-2,7-diyl]-co-1,4-benzo-(2,1,3)-thiadiazole (F8BT) is one of the suitable materials for color-selective organic photoconductive devices owing to its high carrier mobility and absorption coefficient against only the blue light. We investigated a mixing method using a silole derivative, 1,1-dimethyl-2,3,4,5-tetraphenylsilole (DMTPS), in F8BT to improve the ratio between photocurrent and dark current (ON/OFF ratio), which is an important parameter for practical organic photoconductive devices. These organic materials can be coated by a solution process, which leads us to realize a low fabrication cost and a large device area in the future. By adding DMTPS into F8BT, the maximum improvement in ON/OFF ratio of 5 times was achieved compared with the reference device with F8BT only; however, the external quantum efficiency was independent of the concentration of DMTPS less than 50 wt %. In addition, the wavelength selectivity of DMTPS:F8BT in the visible wavelength region was almost the same as that of F8BT only. This result indicates that the DMTPS:F8BT layer can absorb only the blue light, indicating the possibility of a color separation without a prism for high-resolution cameras by combining the green- and red-sensitive devices.

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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.