Jens Hartung

Reductive and brominative termination of alkenol cyclization in aerobic cobalt-catalyzed reactions.

Tetrahydrofur-2-ylmethyl radicals were stereoselectively generated from substituted pent-4-en-1-ols in aerobic cobalt(II)-catalyzed oxidations. Intermediates were trapped with cyclohexa-1,4-diene, gamma-terpinene, BrCCl(3), diethyl dibromomalonate, or electron-deficient olefins such as acrylonitrile or dimethyl fumarate to afford functionalized tetrahydrofurans in synthetically useful yields.

Organic Radical Reactions Associated with Nitrogen Monoxide

5.1. Combination 4505 5.1.1. Alkyl Radical Trapping 4505 5.1.2. Vinyl Radical Trapping 4507 5.1.3. Oxyl Radical Trapping 4507 5.2. Homolytic Substitution 4508 5.2.1. Carbon Radical Substitution 4508 5.2.2. Oxyl Radical Substitution 4509 5.3. Addition 4509 5.3.1. Formation of Nitrogen Carbon Bonds 4509 5.3.2. Formation of Nitrogen Nitrogen Bonds 4510 5.4. Pericyclic Reactions 4512 5.5. Electron Transfer 4513 6. Concluding Remarks 4513 7. References 4514

On the reactivity of bromoperoxidase I (Ascophyllum nodosum) in buffered organic media: formation of carbon bromine bonds.

Peroxidase (PO) activity of vanadate(V)-dependent bromoperoxidase (BPO) I (Ascophyllum nodosum) [VBrPO(AnI)] was retained with a half-life time of ~60 days, if stored in H2O2-incubated, morpholin-4-ethane sulfonic acid (MES)-buffered aqueous alcoholic solutions. These conditions were applied for converting bromide and, e.g., methyl pyrrole-2-carboxylate into bromopyrroles with an almost quantitative peroxide yield. δ,ε-unsaturated alcohols furnished β-bromohydrins and products of bromocyclization, i.e., tetrahydrofurans and tetrahydropyrans (70–84 % mass balance), if treated with H2O2, KBr, and VBrPO(AnI) in phosphate-buffered, CH3CN-diluted media.

Bromoperoxidase activity and vanadium level of the brown alga Ascophyllum nodosum.

Vanadium-dependent peroxidase activity in extracts of Ascophyllum nodosum growing in the intertidal region close to Roscoff/France, and algal vanadium levels, followed approximately similar seasonal variation, as deduced from a study lasting from April 2005 to March 2006. High peroxidase (PO) activity was found in extracts obtained from algae collected in between midwinter to spring [approximately 100-190 U per g dry mass (dm), triiodide assay] with a maximum in April. Periods of reduced PO activity lasted from summer to early winter (approximately 50-90 U per g dm). High vanadium levels (1.5-2.2 mg kg(-1)dm) were found in algae collected from midwinter to spring, whereas reduced levels (0.6-1.4 mg kg(-1)dm) were found in summer to early winter.