The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. 
The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. 
The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. 
The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

Asymmetric 1,3-Dipolar Cycloaddition Reactions

Over the last decade, substantial research has led to the introduction of an impressive number of efficient procedures which allow the selective construction of CC bonds by directly connecting two different CH bonds under oxidative conditions. Common to these methodologies is the generation of the reactive intermediates in situ by activation of both CH bonds. This strategy was introduced by the group of Li as cross-dehydrogenative coupling (CDC) and discloses waste-minimized synthetic alternatives to classic coupling procedures which rely on the use of prefunctionalized starting materials. This Review highlights the recent progress in the field of cross-dehydrogenative C sp 3C formations and provides a comprehensive overview on existing procedures and employed methodologies.

The Cross-Dehydrogenative Coupling of C sp 3H Bonds: A Versatile Strategy for CC Bond Formations

This review gives a survey on the latest most representative developments and progress concerning ionic liquids, from their fundamental properties to their applications in catalytic processes. It also highlights their emerging use for biomass treatment and transformation.

Ionic liquids and catalysis: Recent progress from knowledge to applications

NMR Studies of Cyclodextrins and Cyclodextrin Complexes

The Local Structure of Ionic Liquids: Cation–Cation NOE Interactions and Internuclear Distances in Neat [BMIM][BF4] and [BDMIM][BF4]

Evidence for a molecule-induced homolysis of dimethyldioxirane by several classes of organic compounds (alkanes, alkenes, ethers, alcohols, aldehydes, iododerivatives) is reported. Carbon-centered radicals, arising from alkanes, ethers, and aldehydes, are trapped by CBrCl3 or protonated quinolines. The dramatic influence of oxygen in these reactions, as well as the formation of products of induced homolysis of the dioxirane by carbon-centered radicals (CH4, CH3OH, CH3COOCH3, ROCOCH3, CH3COOCH2COCH3), strongly supports a radical mechanism. With alkenes and iodo derivatives the induced homolysis would lead to diradical intermediates, whose very fast fragmentation would prevent detection, but circumstantial evidence supports a radical mechanism.

Molecule-Induced Homolysis versus “Concerted Oxenoid Oxygen Insertion” in the Oxidation of Organic Compounds by Dimethyldioxirane

Proton Nuclear Magnetic Resonance Spectroscopy Studies of the Inclusion Complex of Piroxicam with β‐Cyclodextrin

Efficient synthesis of optically pure α-(fluoroalkyl)-β-sulfinyl enamines has been achieved by aza-Wittig reaction of triphenyliminophosphoranes with the corresponding α-fluorinated-α‘-sulfinyl ketones. The title compounds 3,4 showed an overwhelming preference for the Z stereochemistry of the enamine form. Their general reactivity has been studied. The reaction with some electrophiles (i.e. benzyl chloroformate and benzyl and allyl bromide) occurs at the nitrogen atom providing the corresponding N,N-disubstituted enamines. Nucleophiles add smoothly to C-2:  heteroatom-centered nucleophiles like methanol, ammonia, and thiophenol afford gem-disubstituted derivatives under thermodynamic control, while a C-centered nucleophile like nitromethane adds in irreversible fashion. The hydride- and deuteride-promoted reduction of 3,4 to the N-Cbz-protected (14) and N-unprotected (15) α-fluorinated-α‘-sulfinyl amines has been studied. Hydride addition was stereoselective, while low stereoselection was obtained with th...

New Versatile Fluorinated Chiral Building Blocks: Synthesis and Reactivity of Optically Pure α-(Fluoroalkyl)-β-sulfinylenamines

The results of the homolytic acylation of compounds containing pyridine and pyrazine rings are reported, aldehydes being used as source of acyl radicals. The reactions proceed in high yields and with complete selectivity at positions α and γ to a heterocyclic nitrogen atom. The factors affecting mono- and poly-substitution and the formation of 9-acyl-9,10-dihydro-derivatives with acridine are discussed. A new process of homolytic acylation, based on decarboxylation of α-keto-acids, is also reported.

Giovanni Fronza

Papers

The Local Structure of Ionic Liquids: Cation–Cation NOE Interactions and Internuclear Distances in Neat [BMIM][BF4] and [BDMIM][BF4]

Molecule-Induced Homolysis versus “Concerted Oxenoid Oxygen Insertion” in the Oxidation of Organic Compounds by Dimethyldioxirane

Proton Nuclear Magnetic Resonance Spectroscopy Studies of the Inclusion Complex of Piroxicam with β‐Cyclodextrin

New Versatile Fluorinated Chiral Building Blocks: Synthesis and Reactivity of Optically Pure α-(Fluoroalkyl)-β-sulfinylenamines

Homolytic acylation of protonated pyridine and pyrazine derivatives