Microbial diversity in waters, sediments and microbial mats evaluated using fatty acid-based methods

The review summarises recent advances towards a greater comprehensive assessment of microbial diversity in aquatic environments using the fatty acid methyl esters and phospholipid fatty acids approaches. These methods are commonly used in microbial ecology because they do not require the culturing of micro-organisms, are quantitative and reproducible and provide valuable information regarding the structure of entire microbial communities. Because some fatty acids are associated with taxonomic and functional groups of micro-organisms, they allow particular groups of micro-organisms to be distinguished. The integration of fatty acid-based methods with stable isotopes, RNA and DNA analyses enhances our knowledge of the role of micro-organisms in global nutrient cycles, functional activity and phylogenetic lineages within microbial communities. Additionally, the analysis of fatty acid profiles enables the shifts in the microbial diversity in pristine and contaminated environments to be monitored. The main objective of this review is to present the use of lipid-based approaches for the characterisation of microbial communities in water columns, sediments and biomats

Stereoselectivity in the double reductive alkylation of pyrroles: synthesis of cis-3,4-disubstituted pyrrolidines

The preparation and Birch reduction of a 1,3,4-tri-substituted pyrrole is described: the heterocycle is loaded with electron-withdrawing groups and undergoes a double reductive alkylation reaction to yield cis-3,4-disubstituted pyrrolidines

The partial reduction of heterocycles: an alternative to the Birch reduction

The partial reduction of a series of heterocycles in THF is described. By adding amine 3 as a proton source and naphthalene as an electron carrier, we were able to produce reductively alkylated pyrrolines and dihydrofurans in moderate to good yields. This reaction does not require liquid ammonia as a solvent, which may have interesting ramifications for large-scale synthesis. Moreover, we were also able to quench the reduction reactions with an acid chloride so performing a reductive acylation reaction. (C) 2000 Elsevier Science Ltd

Stereoselective reductive alkylation of 2,5-disubstituted pyrroles: a role for naphthalene in the partial reduction of heterocycles

Lithium in ammonia promotes the stereoselective reduction of 2,5- disubstituted pyrroles: such reactions proceed with good levels of stereoselectivity, producing the trans-isomer. The stereochemistry of one of the reduced compounds was proven by X-ray crystallography. A mechanism is proposed which explains the stereoselectivity and a modification made to the reducing system that includes catalytic naphthalene and obviates the need for liquid ammonia. (C) 2000 Elsevier Science Ltd

The birch reduction of 3-substituted pyrroles

The Birch reduction of electron-deficient 3-substituted pyrroles is described. Use of a reductive alkylation procedure involving sodium metal in liquid ammonia gave good yields of 4-alkyl-2-pyrrolines. The identity of these products was proven by an X-ray structure of a crystalline derivative. Moreover, the pyrroles used in this study could be readily prepared by reaction of TOSMIC with acrylic amides and esters and, once the reduction was complete, the ester activating group could be easily removed to yield the corresponding N-protected β-proline derivatives