Stereoselective Total Synthesis of 4‐Ketoclonostachydiol

An efficient stereoselective total synthesis of the bioactive 14‐membered natural macrocyclic bislactone 4‐ketoclonostachydiol is described. The strategy involves a Jacobsen's hydrolytic kinetic resolution (HKR), epoxide opening, MacMillan α‐hydroxylation, Horner? Wadsworth? Emmons olefination, a Grignard reaction, and Hoveyda? Grubbs‐II‐catalyzed ring‐closing metathesis (RCM) as key steps.     

Silica‐supported Perchloric Acid Catalyzed One‐pot Synthesis of 1,4‐Dihydropyridines

An environmentally friendly and highly efficient procedure for the preparation of 1,4‐dihydropyridines by the reaction between α,β‐unsaturated aldehydes, aromatic amines and β‐keto esters in the presence of silica supported perchloric acid is described.     

Synthesis and Characterization of Compounds Potentially Related to the Janus Kinase Inhibitor Baricitinib

Russian Journal of Organic Chemistry - Nine compounds potentially related to the Janus kinase inhibitor Baricitinib have been identified, synthesized by conventional methods, and characterized by...     

Stereoselective synthesis of the densely functionalized C1-C9 fragment of amphidinolides C and F

The synthesis of the C1-C9 subunit of amphidinolides C and F is described. Key steps include tandem Sharpless asymmetric dihydroxylation-S_N2 cyclization reaction, Lewis acid-mediated epoxide opening, Wittig reaction, and Wacker oxidation.     

Observation of sub-poisson photon statistics in the cavity-QED microlaser

We have measured the second-order correlation function of the cavity-QED microlaser output and observed a transition from photon bunching to antibunching with increasing average number of intracavity atoms. The observed correlation times and the transition from super- to sub-Poisson photon statistics can be well described by gain-loss feedback or enhanced-reduced restoring action against fluctuations in photon number in the context of a quantum microlaser theory and a photon rate equation picture. However, the theory predicts a degree of antibunching several times larger than that observed, which may indicate the inadequacy of its treatment of atomic velocity distributions.     

Icosahedral B12, macropolyhedral boranes, β-rhombohedral boron and boron-rich solids

The preference for icosahedral B₁₂ amongst polyhedral boranes and elemental boron is explained based on an optimization of overlap model. The ingenious ways in which elemental boron and boron-rich solids achieve icosahedron-related structures are explained by a fragment approach. The Jemmis mno rules are used to get the electron requirements. The extra occupancies and vacancies in β-rhombohedral structures are shown to be inevitable results of electron requirements. The detailed understanding of the structure suggests ways of doping β-rhombohedral boron with metals for desired properties. Theoretical studies of model β-rhombohedral solids with metal dopings provide support for the analysis.     

Shedding Light on the Extinction‐Enhancement Duality in Gold Nanostar‐Enhanced Raman Spectroscopy

Surface‐enhanced Raman spectroscopy (SERS) has evolved from an esoteric physical phenomenon to a robust and effective analytical method recently. The need of addressing both the field enhancement and the extinction of nanoparticle suspensions, however, has been underappreciated despite its substantive impact on the sensing performance. A systematic experimental investigation of SERS enhancement and attenuation is performed in suspensions of gold nanostars, which exhibit a markedly different behavior in relation to conventional nanoparticles. The relationship is elucidated between the SERS enhancement and the localized surface plasmon resonance band, and the effect of the concentration of the gold nanostars on the signal propagation is investigated. It is shown that an optimal concentration of gold nanostars exists to maximize the enhancement factor (EF), and the maximum EF occurs when the LSPR band is blue‐shifted from the excitation wavelength rather than at the on‐resonance position.     

Exocyclobutadieneite

This communication describes a novel structural-type that could be the basis for a potentially new allotrope of C. The novel structural-type is called “exocyclobutadieneite”, and it is thus named for the 1,3-dimethylenecyclobutane generating fragment that the lattice is based upon. It is a 3-,4-connected network consisting of slightly distorted tetrahedral vertices, and slightly distorted pairs of trigonal planar vertices. The lattice can be derived from a known mineral structure called Cooperite (PtS or PdO) by a topologically isomorphic substitution of trigonal planar atom pairs, for square planar vertexes, in the parent Cooperite unit cell. As such, the new pattern bears a distinct counterpoint relationship with its sibling structural-type called the glitter lattice, which has already been described by the authors in several other papers. And whereas glitter is generated by a topologically isomorphic substitution of trigonal planar atom pairs for the square planar vertices in the Cooperite unit cell, in a fashion that extends the unit cell vertically along the crystallographic c-axis, the exocyclobutadieneite structure is generated, in counterpoint, by such an isomorphic substitution that extends the unit cell horizontally along the a- and b-axes. Both the resulting glitter and exocyclobutadieneite structural-types possess AB $_{2}$ stoichiometry (where A is a tetrahedral vertex and B is a trigonal planar vertex) and both occur in the tetragonal symmetry space group P4 $_{2}$ /mmc (#131). The networks differ, however, in the special positions adopted by the vertices in the resultant unit cells, and in their respective topology, as is evidenced by consideration of the Wells point symbols and Schläfli symbols for the 2 tetragonal networks. These differences are illustrated further in the course of the discussion to follow.     

High-speed synthetic aperture microscopy for live cell imaging

We present a high-speed synthetic aperture microscopy for quantitative phase imaging of live biological cells. We measure 361 complex amplitude images of an object with various directions of illumination covering an NA of 0.8 in less than one-thirteenth of a second and then combine the images with a phase-referencing method to create a synthesized phase image. Because of the increased depth selectivity, artifacts from diffraction that are typically present in coherent imaging are significantly suppressed, and lateral resolution of phase imaging is improved. We use the instrument to demonstrate high-quality phase imaging of live cells, both static and dynamic, and thickness measurements of a nanoscale cholesterol helical ribbon.     

Novel oxadiazole functionalized pyridopyrimidine derivatives; their anticancer activity and molecular docking studies

A series of novel oxadiazole functionalized pyridopyrimidine derivatives prepared starting from 6-methyl/ethyl-2-oxo-4-(trifluoromethyl)-1,2-dihydropyridine-3-carbonitrile 1 . This compound 1 on reaction with sulfuric acid obtained compound 2 , further compound 2 on reaction with chloroacetamide followed by reaction with ethoxy methylene malonic diethyl ester coupling and further cyclization to obtain compound 5 . Compound 5 on reaction with hydrazide hydrate obtained hydrazide derivatives 6 . Compound 6 on reaction with diverse substituted aromatic acids to get oxadiazole derivatives 7a–l . All the final compounds 7a–l evaluated for anticancer activity against four human cancer cell lines such as HeLa—cervical cancer (CCL-2); COLO 205—colon cancer (CCL-222); HepG2—liver cancer (HB-8065); and MCF7—breast cancer (HTB-22) and promising compounds 7d and 7k have been identified and evaluated for molecular docking interactions.