Highly enantioselective synthesis of silahelicenes using Ir-catalyzed [2+2+2] cycloaddition

Silahelicenes, which contain two silole moieties in a helically chiral structure, were synthesized by a chiral Ir-catalyzed intermolecular [2+2+2] cycloaddition of tetraynes with diynes along with a Ni-mediated intramolecular [2+2+2] cycloaddition. The photophysical properties of the obtained highly enantiomerically enriched silahelicenes (up to 93% ee) were also measured.     

Silicon Oxide Coatings with Very High Rates (>10?nm/s) by Hexamethyldisiloxane-Oxygen Fed Atmospheric-Pressure VHF Plasma: Film-Forming Behavior Using Cylindrical Rotary Electrode

Silicon oxide films are deposited in atmospheric-pressure (AP) He/O₂/HMDSO plasma excited by a 150?MHz VHF power using a cylindrical rotary electrode. The atomic bonding configurations and deposition rate are studied by controlling the O₂ concentration (O₂/HMDSO source ratio) and VHF power density, the other parameters being maintained constant. Under the addition of 0.03?% O₂ to the process gas mixture (O₂/HMDSO????0.09), AP-VHF plasma greatly enhances the fragmentation and oxidation of HMDSO, so that an almost inorganic film is obtained at a very high deposition rate of 33?nm?s^?1. A silicon oxide coating on a polycarbonate pane is demonstrated with no significant thermal deformation of the pane, showing that AP-VHF plasma would be an efficient coating tool for polymer substrates.     

Sigmasigma* transition in anti,cisoid alternating oligosilanes: clear-cut evidence for suppression of conjugation effect by a cisoid turn

On the basis of the UV absorption spectra of the anti,cisoid alternating oligosilanes, the first experimental clear-cut evidence was presented for the generally accepted idea that the sigma conjugation in polysilanes does not effectively extend through a tetrasilane fragment with a small dihedral angle such as a cisoid turn.     

Stereoselective synthesis of CF3-substituted aziridines by Lewis acid-mediated aziridination of aldimines with diazoacetates

Treatment of trifluoroacetaldehyde N,O-acetal with diazoacetate in the presence of a Lewis acid furnished CF₃-substituted aziridinecarboxylates in good yields. Both cis and trans isomers were obtained stereoselectively by the proper choice of the ester substituents. Use of a chiral diazoacetate derived from (R)-pantolactone led to highly diastereoselective aziridination (94% de).     

trans-2,2'-Bi(1-phenyladamantylidene): the most twisted biadamantylidene

The Grignard coupling of 2,2-dibromo-1-phenyladamantane gave trans-2,2'-bi(1-phenyladamantylidene) (1-Ph). Single-crystal X-ray analysis indicated that 1-Ph has a 23.2 degrees twisted double bond, which is much more distorted than that of parent 2,2'-biadamantylidene (1-H) and that of the ethyl-substituted derivative (1-Et). A cyclic voltammogram showed a reversible electron oxidation wave at 0.87 V vs Fc/Fc(+), which is 0.19 V lower than 1-H, indicating a significant increase in the HOMO energy level due to the distortion. The reaction of 1-Ph with 0.9 equiv of bromine gave an intramolecular Friedel-Crafts alkylation product, while bromination of 1-H and 1-Me has been reported to give a bridged bromonium ion and a rearranged product, 2-(1-methyl-2-adamantylidene)-4-bromotricyclo[5,3,1,0(3.9)]undec-4-ene, respectively.     

Raman spectroscopic study of the structure of water in aqueous solutions of amphoteric polymers

Methacrylic acid (MA) and [3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC) were polymerized to give amphoteric copolymers with various compositions. The structure and H-bonding of water in an aqueous solution of the copolymer were analyzed using the contours of the O-H stretching in the polarized Raman spectra. For comparison, the H-bonded network structure of aqueous solutions of homopolymers (polyMA and polyMAPTAC) was also examined. From the relative intensity of the collective band (C value) corresponding to a long range coupling of the O-H stretching in the aqueous polymer solutions, the number of H-bonds disrupted due to the presence of one monomer residue of the polymers (Ncorr) was determined. The Ncorr value for polyMA was largely positive, and with an increase in the content of the MAPTAC residue, the Ncorr value became smaller, and after passing a minimum (which was still slightly positive) at a roughly equivalent molar ratio, the Ncorr value increased again. This is in significant contrast with the larger positive Ncorr values for the homopolymers (both polyMA and polyMAPTAC), and other ordinary polyelectrolytes such as sodium polyethylenesulfonate, poly-L-lysine hydrobromide and sodium polyacrylate. Furthermore, the Ncorr value for the copolymer (MA ratio MAPTAC = 56:44) became much smaller by the neutralization of MA residues in the copolymer with sodium hydroxide, and comparable to those for neutral polymers such as poly(ethylene glycol) and poly(N-vinylpyrrolidone) and zwitterionic polymers such as poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and poly[3-sulfo-N,N-dimethyl-N-(3'-methacryloylaminopropyl)propanaminium inner salt]. The present results clearly indicate that the amphoteric polymers with comparative contents of cationic and anionic groups do not significantly disturb the H-bonded network structure of water, probably due to the counteraction of the electrostatic hydration effect by the proximity between the anionic and cationic side groups.     

A practical synthesis of 4′-thioribonucleosides

A practical synthesis of 4′-thioribonucleosides starting from inexpensive l-arabinose is described. 1,4-Anhydro-2,3-O-isopropylidene-4-thioribitol, which was prepared by using a novel reductive ring-contraction reaction, was converted to the 5-O-silylated sulfoxides. The Pummerer-type thioglycosylation of the sulfoxides gave the 4′-thioribonucleosides stereoselectively.     

Chemically Programmable and Switchable CAR-T Therapy

Although macromolecules on cell surfaces are predominantly targeted and drugged with antibodies, they harbor pockets that are only accessible to small molecules and constitutes a rich subset of binding sites with immense potential diagnostic and therapeutic utility. Compared to antibodies, however, small molecules are disadvantaged by a less confined biodistribution, shorter circulatory half-life, and inability to communicate with the immune system. Presented herein is a method that endows small molecules with the ability to recruit and activate chimeric antigen receptor T cells (CAR-Ts). It is based on a CAR-T platform that uses a chemically programmed antibody fragment (cp-Fab) as on/off switch. In proof-of-concept studies, this cp-Fab/CAR-T system targeting folate binding proteins on the cell surface mediated potent and specific eradication of folate-receptor-expressing cancer cells in vitro and in vivo.     

Total Synthesis of Zephycarinatines via Photocatalytic Reductive Radical ipso-Cyclization

We report herein a nonbiomimetic strategy for the total synthesis of the plicamine-type alkaloids zephycarinatines C and D. The key feature of the synthesis is a stereoselective reductive radical ipso-cyclization using visible-light-mediated photoredox catalysis. This cyclization enabled the construction of a 6,6-spirocyclic core structure through the addition of a carbon-centered radical onto the aromatic ring. Biological evaluation of zephycarinatines and their derivatives revealed that the synthetic derivative with a keto group displays moderate inhibitory activity against LPS-induced NO production. This approach could offer future opportunities to expand the chemical diversity of plicamine-type alkaloids as well as providing useful intermediates for their syntheses.