Abstract A DNA building block with tunable rigidity was constructed, and the corresponding hydrogel formation process investigated accordingly. high demonstrated to facilitate fast gelation. Different gelation pathways of rigid flexible blocks were revealed, a cyclized dimer intermediate proposed. The energy barrier ring-opening also shown play fundamental role in determining kinetics. Furtherm...

We have presented a systematic small angle neutron scattering investigation of ring–linear blends, where we vary either the ring volume fraction for given in long linear matrix or length at low fraction. found that radius gyration (Rg) shrinks with increasing and nearly reaches Rg melt ϕR = 0.5. At same time, fractal dimension, which is close to Gaussian conformation ϕR, decreases value melt. A...

Cobalt-porphyrin-catalysed intramolecular ring-closing C-H bond amination enables direct synthesis of various N-heterocycles from aliphatic azides. Pyrrolidines, oxazolidines, imidazolidines, isoindolines and tetrahydroisoquinoline can be obtained in good to excellent yields in a single reaction step with an air- and moisture-stable catalyst. Kinetic studies of the reaction in combination with ...

Cholesterol is one of the most ubiquitous compounds in nature. The 9,10-seco-pathway for the aerobic degradation of cholesterol was established thirty years ago. This pathway is characterized by the extensive use of oxygen and oxygenases for substrate activation and ring fission. The classical pathway was the only catabolic pathway adopted by all studies on cholesterol-degrading bacteria. Stero...

The transition structures of the thione-to-thiol rearrangement of O-(2-dimethylaminoethyl and 2-methylthio-) S-methyl xanthates in several solvents were located by semiempirical molecular orbital method (PM3) using the conductor-like screening model (COSMO) approach. Each transition state transforms into the ion-pair intermediate with a three-membered ring structure (aziridinium or thiiranium),...

A concise enantioselective synthesis of the advanced intermediate 5 for the synthesis of pumiliotoxins (Gallagher's intermediate) is described. The synthesis started from the regio- and trans-diastereoselective (dr = 98:2) reductive 3-butenylation of (R)-3-(tert-butyldimethylsilyloxy)glutarimide 14. After O-desilylation and Dess-Martin oxidation, the resulting keto-lactam 10 was subjected to a ...

Addition of low order phenyldimethylsilylcyanocuprates to allenes followed by "in situ" reaction of the intermediate silylcuprate with electrophiles ("the silylcuprate strategy") provides new routes for the synthesis of functionalised allylsilanes, which undergo highly stereocontrolled silicon-assisted intramolecular cyclizations leading to three to seven membered ring-formation.

Bioisosteric analogues of pachastrissamine that contain sulfur and selenium atoms replacing the oxygen in the ring system, were efficiently prepared from a cyclic sulfate intermediate by sequential intermolecular and intramolecular S(N)2 displacement reactions of the dianions. The analogues exhibited cytotoxicities comparable to that of pachastrissamine.

The first enantioselective total syntheses of virosaine A and bubbialidine are described. Key transformations include the formation of a tetracyclic intermediate via an intramolecular aza-Michael addition, generation of a N-hydroxy-pyrrolidine through a Cope elimination and an intramolecular [1,3]-dipolar cycloaddition to generate a complex 7-oxa-1-azabicyclo[3.2.1]octane ring system.

This paper presents an algorithm for computing algebraically relative resolvents which enhances an existing algorithm by avoiding the accumulation of superfluous powers in the intermediate computations. The superfluous power generated at each step is predetermined over a certain quotient ring. As a byproduct, an efficient algorithm for extracting an n-th root of a univariate polynomial is obtai...