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贝耶-维利格单氧化酶催化细菌类核结构成熟的产品选择性

  • 0Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Department of Natural Product Biotechnology, Helmholtz Centre for Infection Research (HZI) and Department of Pharmacy at Saarland University, Campus E8.1, 66123 Saarbrücken, Germany.

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Reactions of Aldehydes and Ketones: Baeyer–Villiger Oxidation 01:22

4.1K

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The carbonyl center is...

Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule 02:17

14.1K

If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...

Regioselectivity and Stereochemistry of Hydroboration 02:36

8.1K

A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn...

Regioselectivity of Electrophilic Additions-Peroxide Effect 02:35

8.5K

In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.

In the first...

Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry 01:29

4.6K

Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.

Dienophiles with one or more electron-withdrawing substituents form stereochemically different products in which the substituents are oriented in an endo (towards) or exo (away) configuration relative to the double bond.

The endo isomer is formed faster and is the kinetic product. The exo isomer is more stable and is the thermodynamic...

Aldol Condensation with β-Diesters: Knoevenagel Condensation 01:27

3.0K

The Knoevenagel condensation is an aldol-type reaction involving the condensation of aldehydes or ketones with active methylene compounds such as β-diesters to produce substituted olefins.

The reaction is catalyzed by amine base, which abstracts the acidic α hydrogen of the activated methylene to generate a resonance stabilized enolate ion. The basic strength of the amine is insufficient to form the enolate of aldehydes or ketones. However, it acts as a nucleophile that attacks the carbonyl...