594-34-3Relevant articles and documents
REACTION OF ACETYLENIC AND VINYLIC ORGANOLITHIUM REAGENTS WITH TRIETHOXYCARBENIUM TETRAFLUOROBORATE: PREPARATION OF α-ACETYLENIC AND α-ETHYLENIC TRIETHYL ORTHOCARBOXYLATES
Picotin, G.,Miginiac, Ph.
, p. 249 - 254 (1987)
Acetylenic and vinylic liyhium derivatives react with triethoxycarbenium tetrafluoroborate to give α-unsaturated triethyl orthocarboxylates.
Synthesis of the stereoisomers of a novel antibacterial agent and interpretation of their relative activities in terms of a theoretical model of the penicillin receptor
Wolfe,Zhang,Johnston,Kim
, p. 1066 - 1075 (2007/10/02)
2,2-Dimethyl-3-(2'-hydroxypropyl)-5-carboxy-Δ3-1,4-thiazine (1) is a designed antibacterial agent. Based on an analysis of how penicillin complexes to and reacts with a model of a penicillin-binding protein, 1 contains a functional group (C=N) that can react with a serine hydroxyl group of the receptor according to the putative reaction Enz-OH + C=N → Enz-O-C-NH. Compound 1 also contains additional substituents that are designed to position the O-H and C=N groups relative to one another in the enzyme-substrate complex in a geometry that attempts to reproduce the optimum geometry of approach of two such reactants. A most important assumption is that this optimum geometry can be computed ab initio. In a first preparation of 1, (±)-5-methyl-4-hexene-2-ol (2) was converted to the lithium salt of (±)-2-mercapto-2-methyl-5-tert-butyldimethylsiloxy-3-hexanone (7), which was condensed with the N-tert-butoxycarbonyl-D- and L-serine-β-lactones (3). The synthesis was completed by deprotection with formic acid and cyclization in water. The R and S enantiomers of 2 have now been obtained, and the absolute configuration of the alcohol established, by reaction of the R- and S-propylene oxides with an organometallic reagent prepared from β,β-dimethylvinyl bromide. The R alcohol has also been secured by lipase-catalyzed transesterification with trifluoroethyl butyrate, and chemical hydrolysis of the trifluoroethyl ester. The R and S enantiomers of 2 were converted to the R and S enantiomers of 7, and these were condensed with the R and S enantiomers of 3 to yield each of the stereoisomers of the chemically unstable 1 in ca. 95% optically pure form. Antibacterial activity resides in the 5S,8R and 5S,8R isomers. These findings are shown to be consistent with the theoretical model. It is hoped that the stability of the lead structure 1 can be improved, to allow binding experiments with penicillin recognizing enzymes to proceed. 2,2-Dimethyl-3-(2′-hydroxypropyl)-5-carboxy- Δ3-1,4-thiazine (1) is a designed antibacterial agent. Based on an analysis of how penicillin complexes to and reacts with a model of a penicillin-binding protein, 1 contains a functional group (C = N) that can react with a serine hydroxyl group of the receptor according to the putative reaction Enz-OH + C = N → Enz-O-C-NH. Compound 1 also contains additional substituents that are designed to position the O-H and C = N groups relative to one another in the enzyme-substrate complex in a geometry that attempts to reproduce the optimum geometry of approach of two such reactants. A most important assumption is that this optimum geometry can be computed ab initio. In a first preparation of 1, (±)-5-methyl-4-hexene-2-ol (2) was converted to the lithium salt of (±)-2-mercapto-2-methyl-5-tert-butyldimethylsiloxy-3-hex anone (7), which was condensed with the N-tert-butoxycarbonyl-D- and L-serine-β-lactones (3). The synthesis was completed by deprotection with formic acid and cyclization in water. The R and S enantiomers of 2 have now been obtained, and the absolute configuration of the alcohol established, by reaction of the R- and S-propylene oxides with an organometallic reagent prepared from β,β-dimethylvinyl bromide. The R alcohol has also been secured by lipase-catalyzed transesterification with trifluoroethyl butyrate, and chemical hydrolysis of the trifluoroethyl ester. The R and S enantiomers of 2 were converted to the R and S enantiomers of 7, and these were condensed with the R and S enantiomers of 3 to yield each of the stereoisomers of the chemically unstable 1 in ca. 95% optically pure form. Antibacterial activity resides in the 5S,8R and 5S,8S isomers. These findings are shown to be consistent with the theoretical model. It is hoped that the stability of the lead structure 1 can be improved, to allow binding experiments with penicillin recognizing enzymes to proceed.
Solvent Effects on the Rate of Heterolysis of t-Butyl Chloride, Bromide, Iodide, and 2,4-Dinitrophenolate
Mitsuhashi, Tsutomu,Hirota, Hiroshi,Yamamoto, Gaku
, p. 824 - 830 (2007/10/02)
Rates of heterolytic decompositions of t-butyl chloride, bromide, iodide, and 2,4-dinitrophenolate have been measured by an NMR method in eight deuterated or undeuterated polar solvents; methanol-d4, ethanol-d6, dimethyl-d6 sulfoxide, N,N-dimethylformamide-d7, acetonitrile-d3, pyridine, nitrobenzene, and acetone-d6.The observed solvent effect is discussed on the basis of cation and anion solvation.With t-butyl halides, the anion solvation due to hydrogen bonding by protic solvents drastically decreases on increasing the radius of halide ions, and thus the differential solvation transferred from anion-solvating methanol to cation-solvating dimethyl sulfoxide is dramatically reversed on going from the chloride to the iodide (kMe2SO-d6/kmethanol-d4 at 60 deg C: t-BuCl, 5E-2; t-BuBr, 6E-1; t-BuI, 7).The 2,4-dinitrophenolate behaves like the iodide.Complicated products are obtained in the decomposition of t-butyl bromide in dimethyl sulfoxide; however, a mechanism involving a bimolecular decomposition process of the bromide is ruled out.During the decomposition od t-butyl iodide in dimethyl sulfoxide, an intermediate salt t-butoxydimethylsulfonium iodide has been detected.The salt decomposes to isobutene, but the process is much slower than the heterolytic decomposition of t-butyl iodide itself at ambient temperature.
