Abiotic ammonium formation in the presence of Ni-Fe metals and alloys and its implications for the Hadean nitrogen cycle

Experiments with dinitrogen-, nitrite-, nitrate-containing solutions were conducted without headspace in Ti reactors (200°C), borosilicate septum bottles (70°C) and HDPE tubes (22°C) in the presence of Fe and Ni metal, awaruite (Ni80Fe20) and tetrataenite (Ni50Fe50). In general, metals used in this investigation were more reactive than alloys toward all investigated nitrogen species. Nitrite and nitrate were converted to ammonium more rapidly than dinitrogen, and the reduction process had a strong temperature dependence. We concluded from our experimental observations that Hadean submarine hydrothermal systems could have supplied significant quantities of ammonium for reactions that are generally associated with prebiotic synthesis, especially in localized environments. Several natural meteorites (octahedrites) were found to contain up to 22 ppm Ntot. While the oxidation state of N in the octahedrites was not determined, XPS analysis of metals and alloys used in the study shows that N is likely present as nitride (N3-). This observation may have implications toward the Hadean environment, since, terrestrial (e.g., oceanic) ammonium production may have been supplemented by reduced nitrogen delivered by metal-rich meteorites. This notion is based on the fact that nitrogen dissolves into metallic melts

Studies on the role of conformation and of hydrogen-bonding on the dihydroxylation of cyclic allylic alcohols: Application to the synthesis of conduritol D

A study on the dihydroxylation of a series of conformationally 'locked' cyclohexenols is reported. The orientation of the hydroxy group (i.e. equatorial or axial) is crucial in determining the degree of diastereoselectivity observed during oxidation. In some cases, the use of hydrogen-bonding enables the stereoselective synthesis of syn triols and tetraols. This effect has been utilised in the synthesis of conduritol D: X-ray crystal structure analysis provided a method of assigning the relative and absolute stereochemistry of an advanced synthetic intermediate

Reduction of electron-deficient pyrroles using group I and II metals in ammonia

The preparation and Birch reduction of a series of electron-deficient pyrroles is described. This methodology allows the synthesis of a variety of C-2 substituted 3-pyrrolines in good to excellent yields. The role of various activating groups (amide, ester, carbamate and urea) has been examined with regard to both stability under the Birch conditions and ease of deprotection after reduction. In addition, we discovered that the 3-pyrroline skeleton can be oxidised at C-5 with chromium trioxide-3,5-dimethylpyrazole to form the 3-pyrrolin-2-one nucleus. The identity of the Birch reduced products and also of the oxidised 3-pyrrolin-2-ones has been confirmed by X-ray crystallography on two derivatives

The structural characterization of amavadin

WOS: 000079232700010PubMed ID: 2971181

Investigations of Amavadin

2nd Symposium on Biological Aspects of Vanadium -- AUG 16-17, 1999 -- BERLIN, GERMANYWOS: 000087817300004PubMed ID: 10885458The development of the understanding of the co-ordination chemistry and the properties of Amavadin, the chemical form in which vanadium is accumulated by the Amanita genus of mushrooms, is reviewed. (C) 2000 Elsevier Science Inc. All rights reserved