A new route to (±)-erythro-roccellic acid and chaetomellic anhydride C through functional rearrangement, promoted by n-propylamine or CH3ONa/CH3OH, of N-propyl-3-chloro-4-dichloromethyl-3-dodecylpyrrolidin-2-one

The rearrangement of a trichloro-pyrrolidin-2-one, prepared by the CuCl-TMEDA catalyzed atom transfer radical cyclization of N-alkyl-N-(3-chloro-2-propenyl)-2,2-dichloromyristamide, with n-propylamine or CH₃ONa/CH₃OH, is the key step of a new, short and inexpensive route to chaetomellic anhydride C and (±)-erythro-roccellic acid.     

Phosphonyl radical addition to enol ethers. The stereoselective synthesis of cyclic ethers

Addition of diethyl phosphite or diethyl thiophosphite to enol ethers, in the presence of a radical initiator, results in the regioselective synthesis of organophosphonate or phosphonothioate derivatives, respectively, under mild conditions. This method can be applied to the stereoselective formation of substituted tetrahydrofurans and tetrahydropyrans, on cyclisation of vinyl ethers bearing unsaturated side chains.     

DNA Responds to Ionizing Radiation as an Insulator,Not as a “Molecular Wire”

The yields of radicals trapped on DNA, measured by EPR spectroscopy of oligodeoxyribonucleotide crystals (the EPR spectrum of a single crystal of d(CCCTAGGG) is shown), are found to be very high (0.7 μmol J⁻¹) and insensitive to long-range (>10⁶ base pairs) versus short-range stacking (8 base pairs) of the bases. These observations are evidence that DNA at 4 K has the properties of an insulator and argue against DNA acting as a “molecular wire”.     

Trapping of an Organic Radical by an O=CrVI Function

Not only capable of generating organic radicals by H abstraction, chromyl chloride can also trap them again (see scheme). This is confirmed by the crystal structure of a Cr^V oxo alkoxide, which was formed in three successive steps when bisadamantylidene oxide was allowed to react with CrO₂Cl₂.     

Interaction of Qinghaosu (Artemisinin) with Cysteine Sulfhydryl Mediated by Traces of Non-Heme Iron

The antimalarial action of 1,2,4-trioxanes such as qinghaosu (QHS) may take place through the mechanism shown schematically: In the presence of cysteine traces of non-heme iron (FeSO₄) may cleave the peroxy bond of QHS rapidly, and the transient carbon-centered radical can attack the sulfur ligand to form a covalent bond.     

A New Anion-Trapping Radical Host, [(Cu-dppe)3{hat-(CN)6}]2+

Anions PF ₆ ⁻ and CF ₃ SO ₃ ⁻ are trapped by the new radical host [(Cu-dppe)₃{hat-(CN)₆}]²⁺, which was synthesized in a one-pot reaction from a copper(I ) source, hat-(CN)₆, and dppe in acetone. The trapped salts have been characterized both in solution and in the solid state (see picture: A⁻: PF₆⁻, CF₃SO₃⁻). hat-(CN)₆=hexaazatriphenylene hexacarbonitrile; dppe=1,2-bis(diphenylphosphanyl)ethane.     

Flight from the Tyranny of Tin: The Quest for Practical Radical Sources Free from Metal Encumbrances

An urgent search is being made for generic reagents that promote free radical synthetic transformations as means of banishing the toxic threat of organotin hydrides. Although second-generation tin reagents are beguiling, organosilanes and a range of thiocarbonyl compounds are more intrinsically benign. Metal-free radical chain sequences based around cyclohexadiene derivatives are being developed (see reaction scheme), and tetrathiafulvalenes mimic metals and allow a crossover from homolytic to ionic chemistry. Z=alkene.     

Radical Cyclization/β-Elimination Tandem Reactions: Enantiopure Sulfoxides as Temporary Chiral Auxiliaries

Alkylidene-substituted cyclopentane derivatives are formed in high enantiomeric purity by the reaction shown below. A highly diastereoselective radical cyclization is followed by elimination of a β-sulfinyl radical. Interestingly, the addition of the Lewis acid methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) totally reverses the stereochemical outcome of the reaction. E=CO₂Me.     

Direct Observation of Radical Intermediates While Investigating the Redox Behavior of Thiamin Coenzyme Models

The redox behavior of “active aldehydes” 1 ⁻ derived from 3-benzylthiazolium salts and simple aldehydes in the presence of a base has been examined with low-temperature cyclic voltammetry and EPR spectroscopy. The highly negative oxidation potentials of 1 ⁻ and the spin distribution of the intermediate radicals 1 ^. indicate that the active aldehyde can act as an efficient electron mediator in thiamin-dependent enzymatic redox systems.