Dialkylboryl-Substituted Cyclic Disilenes Synthesized by Desilylation-Borylation of Trimethylsilyl-Substituted Disilenes

π-Electron systems of silicon have attracted attention because of their narrow HOMO-LUMO gap and high reactivity, but the structural diversity remains limited. Herein, new dialkylboryl-substituted disilenes were synthesized by the selective desilylation-borylation of the corresponding trimethylsilyl-substituted disilenes. The dialkylboryl-substituted disilenes were fully characterized by a combination of NMR spectroscopy, MS spectrometry, single-crystal X-ray diffraction analysis, and theoretical calculations. The longest-wavelength absorption bands of boryldisilenes were bathochromically shifted compared to the corresponding silyl-substituted disilenes, indicating a substantial conjugation between π(Si=Si) and vacant 2p(B) orbitals. In the presence of 4-(dimethylamino)pyridine (DMAP), the dialkylboryl groups in the boryl-substituted disilenes were easily converted to trimethylsilyl groups, suggesting the dialkylboryl-substituted disilenes in the presence of a base serve as the surrogates of disilenyl anions (disilenides).     

A Remark on Support of the Principal Function for Class A Operators

Let be an invertible class A operator such that . Then we show that , where gT is the principal function of T. Moreover, we show that if T is pure, then .     

Synthesis and properties of O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl cellulose

In this article, a series of O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl celluloses with different degree of substitution (DS) values was synthesized by a homogeneous reaction of cellulose with 2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl chloride in a 10% (w/w) dimethylacetamide/lithium chloride solution, combined with pyridine as the acid acceptor. The total DS values of the derivatives in anhydroglucose units was determined by ¹H and ¹³C NMR spectra, and ranged from 0.4 to 3.0, depending on the amount of acid chloride in the reaction. The effects of the total DS values and the O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl substituent distribution on the solubility of the derivatives were investigated. The lowest limit of the DS value for water‐soluble O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl cellulose was approximately 0.5, which is lower than that of methylcellulose. The amphiphilic derivatives with higher DS values than 1.7 exhibited a good solubility in both water and organic solvents, such as dimethyl sulfoxide, tetrahydrofuran, and chloroform. Sol‐gel transition in aqueous solution was observed for the amphiphilic derivatives with a higher DS value than 1.7; the precipitation temperature (T_p) decreased as the DS value increased, showing that the derivatives are highly temperature sensitive. The thermal properties of the fully substituted derivative were measured using polarized microscopy, DSC, and X‐ray diffraction; and are discussed in terms of phase transition of the sample derivatives. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 376–382, 2001     

Methods of Split Reporter Reconstitution for the Analysis of Biomolecules

Intracellular signaling inside living cells is controlled by the specific localization of biomolecules, including proteins, with timescales ranging from milliseconds to several hours. To elucidate the related spatial and temporal signal processes, development of optical probes for cellular events is a challenging task in present studies. Herein, we describe recent advances in the basic design of the optical probes, which have been inspired by luminescent creatures, and their practical application to visualize intracellular events in living cells and animals. A discussion of different probe designs reveals their benefits and shortcomings.     

Designing split reporter proteins for analytical tools

A current focus of biological research is to quantify and image cellular processes in living cells and animals. To detect such cellular processes, genetically-encoded reporters have been extensively used. The most common reporters include firefly luciferase, renilla luciferase, green fluorescent protein (GFP) and its variants with various spectral properties. This review describes novel design of split-GFP and luciferase reporters based on protein splicing, and highlights some potential applications with the reporters to study protein-protein interactions, protein localization, intracellular protein dynamics, and protein activity in living cells and animals.     

Akaike's Information Criterion for Stoichiometry Inference of Supramolecular Complexes

“How do we decide the stoichiometry of host–guest complexes?” This question has long been answered by the Job plot since its first report in 1928. However, as the Job plot was claimed to be misleading in 2016, the question became an open question again and called for renewed investigations. An information-theoretic approach, called Akaike's information criterion, is introduced in this study to select the best model of host–guest complexes, which can rank the models with weight of evidence. A few test cases with unique cylindrical hosts were examined to demonstrate the applicability of the information-theoretic method. Consequently, reasonable views over the thermodynamic behaviors of dumbbell-and-cylinder complexes were obtained. Akaike's information criterion can be a useful and superior alternative to statistical null hypothesis testing, which was proposed as a remedy in place of the Job plot.     

Benzyl radical addition reaction through the homolytic cleavage of a benzylic C-H bond

Direct generation of a benzyl radical by C-H bond activation of toluenes and the addition reaction of the resulting radical to an electron deficient olefin were developed. The reaction of dimethyl fumarate with toluene in the presence of Et(3)B as a radical initiator at reflux afforded 2-benzylsuccinic acid dimethyl ester in good yield.     

Synthesis of 6H,8H-isoquino[2,3-c][1,3]benzothiazin-8-ones

6H,8H-Isoquino-1,3-benzothiazin-8-ones have been prepared by reaction of 6,7-dimethoxy-2H-1,3-benzo-thiazines with homophthalic anhydride and by photocyclization of 3-benzoyl-4-methylene-6,7-dimethoxy 2H-1,3-benzothiazine. The compounds are thia analogues of protoberberine alkaloids containing a sulfur atom at C-5 and a lactam function at C-8. The mass spectra of the title compounds are discussed.