The racemization of an optically active sulfilimine and optically active aminosulfonium salts

The racemization of an optically active sulfilimine and optically active aminosulfonium salts was kinetically measured. The mechanism of the racemization of optically active sulfilimine (?)-1 has been established. The activation parameters for the racemization of (?)-1 and (?)-7 were calculated. A plausible pathway for the decomposition of (?)-6, (?)-7 and (?)-8 with tetra-n-butylammonium bromide in the presence of methyl ethyl ketone to provide 3-p-tolylthio-2-butanone 22 is proposed.     

The resolution of an optically active pyridinethiol

The resolution of a chiral pyridine thiol has been eonveniently carried out through derivatives with optically active α-phenethylisoeyanates. Optically active heterocyclic thiols in which the thiol occupies the center of chirality are not known in the literature. In conjunction with a synthetic program dealing with derivatives and analogues of 5-mercaptopyridoxine (1), the preparation of such species was accomplished. Their resolution proved to be difficult, but the techniques devised herein should prove of general utility for other heteroeyclic thiols or alcohols.     

双刚性共轭嵌段共聚物体系的自组装

棒杆-棒杆(rod-rod)共轭嵌段共聚物体系是近几年发展起来的一类新型共轭聚合物材料,由于其特有的电学活性以及通过自组装实现纳米尺度结构可控等特性正逐渐成为人们研究的热点.构筑单元的刚性棒状结构使得rod-rod共轭嵌段共聚物体系倾向于自组装形成囊泡或层状结构等低曲率聚集体.本文总结了近年来关于rod-rod共轭嵌段共聚物体系自组装行为的研究,分别介绍了溶液中以及薄膜状态下双刚性共轭嵌段共聚物体系的自组装行为,在此基础上进一步讨论了rod-rod共轭嵌段共聚物薄膜结构与性能的关系.     

Light scattering by an optically active sphere

The scattering of light by a sphere with intrinsic optical activity is calculated exactly from electromagnetic theory using the constitutive equations appropriate for an optically active, isotropic medium. The resulting scattering matrix is different from that obtained by previous investigators.     

Interactions between a luminescent conjugated oligoelectrolyte and insulin during early phases of amyloid formation

Aggregates of misfolded proteins play an important role in diseases such as Alzheimer's. Here it is demonstrated how the anionic oligothiophene p-FTAA interacts with and influences pre-fibrillar protein assemblies during the earlier stages of in vitro fibrillation. Conjugated polythiophenes have previously been demonstrated to detect and discriminate between different types of protein aggregates and also introduce luminescent or conductive properties to these nanoscale fiber structures. Fluorescence spectroscopy, DLS, TEM and FCS are employed to follow the interplay between p-FTAA and insulin during in vitro fibrillation.     

Self-assembly of conjugated polymers for anisotropic nanostructures

As their potential applications in various electronic devices increase, the preparation of anisotropic conjugated polymer nanostructures are highly desirable. This paper presents a review of the literature and our recent results on the self-assembly of one-, two- and three-dimensional anisotropic nanostructures using conjugated polymers as building blocks, including the formation of one-dimensional (1D) nanofibers and nanotubes, two-dimensional (2D) nanoribbons and nanosheets, and three-dimensional (3D) superstructures. The mechanisms guiding the formation of various nanostructures are analyzed by a cooperative effect of - stacking interaction and other noncovalent interactions.     

Metal-induced supramolecualr chirality in an optically active polythiophene aggregate

Chiral polythiophenes (PTs), in sharp contrast to other optically active polymers, exhibit optical activity in the pi-pi* transition region which is derived from the chirality of the main chain when they self-assemble to form a supramolecular pi-stacked aggregate with intermolecular interactions in a poor solvent or in a film. We now report that the regioregular, optically active PT poly[(R)-3-[4-(4-ethyl-2-oxazolin-2-yl)phenyl]thiophene] (poly-1) exhibits unique split-type induced circular dichroism (ICD) in the pi-pi* transition region of the main chain upon complexation with various metal salts such as trifluoromethanesulfonates of copper(I), copper(II), silver(I), and zinc(II), and iron(II) perchlorate in chloroform, which is a good solvent for poly-1. The appearance of ICD and slight changes in the UV/Vis spectra (no color change), except for the zinc salts, indicated that the chirality may not be induced by chiral pi-stacked aggregates of poly-1, but by the chirality of the main chain, for example, a predominantly one-handed helical structure induced by intermolecular coordination of the oxazoline groups to metal ions. The sign of the Cotton effect depends on the metal salt; most metal salts induced ICDs with similar Cotton-effect patterns, while zinc salts caused an inversion of the signs of the Cotton effect of poly-1 accompanied by a gradual red shift in the absorption of up to 125 nm. The changes in the conformation and the size of the poly-1 aggregates induced by different metal salts were also investigated by (1)H NMR titrations, static light scattering (SLS), atomic force microscopy (AFM), and membrane filtration. On the basis of these results, we propose a possible model for the chiral supramolecular aggregates of poly-1 with metal salts.     

Synthesis of an optically active unsaturated silicohydrocarbon containing an asymmetric silicon atom

Summary Starting with vinyltriethoxysilane, we were the first to obtain optically active dextrorotatory and levorotatory isomers of an unsaturated silicohydrocarbon, namely, of vinylphenyl--naphthylsilane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 387–389, February, 1965     

The conversion of asperuloside to an optically active prostaglandin intermediate

Synthesis of optically active intermediate $\text{1a}$ for PGF_2α or (+)-11-deoxy-11α-hydroxymethyl PGF_2α from asperuloside is described.     

Synthesis of optically active penems

A general synthesis for optically active penems is described. Penems undergo a novel thermal isomerisation reaction.     

Pyridylethylation of optically active amines

Summary A study has been made of the addition of (R)- and (S)-1 phenylethylamines and (R)- and (S)-1cyclohexylethylamines to the C=C bond of 2- and 4-vinylpyridines in the presence of an acid catalyst. The corresponding monoadducts have been synthesized with high preparative yields. By reactions of these adducts with 2- and 4-vinylpyridines, bis-adducts have been obtained. All of the products had high optical purities (9199%, HPLC).Institute of Organic Catalysis, Rostock City University, Rostock 18055. Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 843–850, June, 1995. Original article submitted May 10, 1995.     

Synthesis of optically active lipoaminoacids

Conclusions S--(Distearoyl-L-phosphatidyl)--L-alanylglycerol and its R-isomer have been synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1098–1100, June, 1966.     

Synthesis of optically active bihelicenols

All six stereoisomers of dimethyl 5,5′-dihydroxy-1,1′,12,12′-tetramethyl-[6,6′]bi(benzo[c]phenanthrenyl)-8,8′-dicarboxylate (bihelicenol) were synthesized by the oxidative coupling of methyl 8-hydroxy-1,12-dimethylbenzo[c]phenanthrene-5-carboxylate (helicenol), and their structures were determined by X-ray analysis.