Preparation and regioselective reactions of novel gem-difluorinated vinyloxiranes with some organometallic reagents.
Hitherto unknown, relatively labile gem-difluorinated vinyloxiranes were prepared by difluoro-Wittig reactions with alpha,beta-epoxyketones; for these vinyloxiranes alkyl groups were delivered at the fluorine-attached terminal carbon atom in an SN2' manner by RLi, while Me3Al and MeMgBr-CuCl (3: 1) introduced the Me group at the allylic epoxy carbon with retention and inversion of the original stereochemistry, respectively.
Studying the signaling role of 2-oxoglutaric acid using analogs that mimic the ketone and ketal forms of 2-oxoglutaric acid.
2-Oxoglutaric acid (2-OG), a Krebs cycle intermediate, is a signaling molecule in many organisms. To determine which form of 2-OG, the ketone or the ketal form, is responsible for its signaling function, we have synthesized and characterized various 2-OG analogs. Only 2-methylenepentanedioic acid (2-MPA), which resembles closely the ketone form of 2-OG, is able to elicit cell responses in the cyanobacterium Anabaena by inducing nitrogen-fixing cells called heterocysts. None of the analogs mimicking the ketal form of 2-OG are able to induce heterocysts because none of them are able to interact with NtcA, a 2-OG sensor. NtcA interacts with 2-MPA and 2-OG in a similar manner, and it is necessary for heterocyst differentiation induced by 2-MPA. Therefore, it is primarily the ketone form that is responsible for the signaling role of 2-OG in Anabaena.
Ethoxyvinyl polyfluoroalkyl ketones versatile synthones in fluoroorganic chemistry
Abstract We have found readily available β-ethoxyvinyl trifluoromethyl ketone to be a convenient and comprehensive starting material for the synthesis of various fluoro-containing compounds such as heterocycles, enones, enaminones and chelate complexes. The 4,4,4-trifluoro-3-oxo-l-butenyl group formed by β-ethoxyvinyl trifluoromethyl ketone is a suitable protecting group for the N-H terminal of amino acids in peptide synthesis. The formation of peptides using these protected amino acids occurs without racemization.