10.1039/c2ob06849d
The research focuses on the synthesis and conformational analysis of oxy-substituted butenolide spiroacetals and spiro-N,O-acetals, which are complex organic compounds with potential applications in the synthesis of natural products. The study involves the oxidative spirocyclisation of 2-[(4-hydroxy or 4-sulfonamido)butyl]furans to form the spiroacetals. The experiments utilize techniques such as NMR spectroscopy to investigate the axial–equatorial preference of oxy-substituents, employing an acid-catalysed thermodynamic relay to assess configurational bias. Reactants include 2-(4-hydroxybutyl)furan derivatives, various oxy-substituents, and reagents like OsO4, NMO, and MCPBA for the oxidation steps. The analysis involves crystallographic data for certain compounds, indicated by CCDC references, and discussions on the potential origins of the observed preferences, such as stabilizing gauche effects and solvation influences. The research has implications for the synthesis of bis(acetylenic)enol ether spiroacetals, including AL-1 and related compounds, and provides insights into the conformational preferences that can guide the selection of starting materials and synthetic routes.
10.1016/S0040-4039(00)93423-3
The research aimed to develop a mild and chemoselective method for the oxidation of sulfides to sulfones, a transformation that is challenging due to the scarcity of mild and selective procedures. The study concluded that osmium tetraoxide, when used as a catalyst in conjunction with the co-oxidant N-methylmorpholine-N-oxide (NMO), is highly efficient for this oxidation, requiring only one mole percent to achieve nearly quantitative yields of sulfones from a variety of sulfides. The process is tolerant of other functional groups and can even selectively oxidize sulfides in the presence of olefins.
10.1016/S0040-4020(01)96078-8
The research focuses on the enantioselective syntheses of D- and L-ribo- and arabino-C,S-phytosphingosines, which are biologically important compounds found in plant sphingolipids and human brain and kidney lipids. The purpose of the study was to develop practical syntheses of these homochiral compounds from (R)-2,3-O-isopropylidene glyceraldehyde, utilizing key steps such as (Z)-selective olefination, selective monobenzoylation, Mitsunobu-type introduction of nitrogen, and osmylation. The conclusions drawn from the research indicate that the method is efficient, using inexpensive reagents and simple conditions suitable for gram-scale synthesis, and it also allows for the preparation of N- and O-protected derivatives, which could be useful for incorporating these compounds into biologically active ceramide and cerebroside structures. Chemicals used in the process include (R)-2,3-O-isopropylidene glyceraldehyde, phosphorane, benzoyl chloride, triphenylphosphine, diethyl azodicarboxylate, phthalimide, N-methyl-morpholine-N-oxide, osmium tetroxide, and various other reagents for protection and deprotection steps, as well as for chromatographic separation and analysis.
Xi
