Corrections to the Alder and Winther semiclassical cross section for first order Coulomb excitation are considered through the Sukumar and Brink systematic expansion of the propagator in inverse powers of Sommerfeld’s parameter, η. The zeroth order term is that provided by unsymmetrised Alder-Winther theory and it is shown that to order 1/η the only type of correction is one corresponding to en...

Here we found that the enantioselectivity of G-quadruplex DNA-based Diels-Alder reaction can be switched by just changing Na(+) to K(+), which is ascribed to the structural transformation of the G-quadruplex from antiparallel to hybrid-type. By tuning the ratio of Na(+)/K(+), the enantioselectivity of the Diels-Alder reaction could be switchable and shows much more sensitive to K(+) than to Na(+).

A concise synthesis of forbesione (1) and desoxymorellin (3) is presented. Central to the strategy is a biomimetic Claisen/Diels-Alder/Claisen reaction cascade that proceeds in a regioselective manner and produces the desired scaffold exclusively. The observed regioselectivity and product distribution of the Claisen/Diels-Alder/Claisen reaction are attributed to the electronic effects of the xa...

Electrocatalysis was employed to promote Diels–Alder reactions between electronically mismatched substrates. A catalytic amount of electricity was enough to complete the overall reactions and GC-MS monitoring and CV measurements clearly illustrated the electrocatalytic nature of the reactions, which involve an EC-backward-E mechanism. The electrocatalytic Diels–Alder reactions were rationally d...

A sequential Diels-Alder reaction/silicon-directed [4 + 2]-annulation was developed to assemble hydroisochromene-type ring systems from menadione 2. In the first step, a Diels-Alder of the 1-silyl-substituted butadiene 1 with 2 furnished an intermediate cyclic allylsilane. Subsequently, TMSOTf promoted a [4 + 2]-annulation through trapping of an oxonium, generated by condensation between an ald...

Satellite photo-comparisons indicate extensive expansion of alder (Alnus) shrubs since 1968 within tundra ecotones near Kharp in northwest Siberia. Field observations reveal that nearly all expansion occurred on exposed circles in patterned ground. We mapped the location of alders and circles and measured surface organic thickness, mineral soil thickness, nearsurface soil temperature, shrub hei...

Three new Diels-Alder adducts, macrourins E - G (1: -3: ), one new 2-arylbenzofuran, macrourin H (4: ), and eight known Diels-Alder adducts (5: -12: ) were isolated from Morus macroura. Their structures were elucidated through extensive analysis of spectroscopic data. The 1H NMR and ECD trends in the determination of the configurations of these Diels-Alder adducts were summarized. The tyrosinas...

There is currently a tremendous interest in developing bioorthogonal "click chemistry" methods for the modification of biopolymers. Very recently, inverse-electron-demand Diels-Alder reactions have received attention, but to date they have not been applied to nucleic acids. Here we describe the first example of DNA modification by inverse-electron-demand Diels-Alder reaction. We synthesized fou...

The Carboni-Lindsey reaction between tetrazines and strained unsaturated hydrocarbons has in recent years become a useful tool bioorthogonal chemistry for labelling biomolecules vitro vivo. Here, we report computational studies on the mechanism of Diels-Alder/Retro-Diels-Alder commercially available tetrazine norbornene. Isomerism with norbornene-amide relevant applications bioconjugation chemi...

Alder and conifer soil were examined for Streptomyces spp. and non-filamentous bacteria antagonistic to Phellinus weirii. Conifer soil supported higher populations Streptomyces spp. and higher percentage of Streptomyces species antagonistic to P. weirii than did alder soil. The populations of non-filamentous bacteria were low in both soils. Alder soil, however, had a higher percentage of non-fi...