- Resolution of 1-phenyl-2-(p-tolyl)ethylamine via diastereomeric salt formation
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(S)-1-Phenyl-2-(p-tolyl)ethylamine (S)-1, used for the industrial scale resolution of chrysanthemic acids, was obtained via resolution of the racemate with the hemiphthalate of (S)-isopropylidene glycerol (R)-2. The maximum experimental efficiency [69% yield and >99% e.e. of (S)-1] was achieved by a simple precipitation of (S)-1·(R)-2 from the solution of the 1:1 diastereomeric salt mixture in 93/7 isopropanol/water at saturation of the more soluble (R)-1·(R)-2 salt. Such an experimental efficiency was consistent with 0.79 maximum theoretical resolvability, derived from the solubilities of the two diastereomeric salts, and with DSC data, which indicated that the (S)-1·(R)-2/(R)-1·(R)-2 system is a binary mixture exhibiting an eutectic with composition approximately corresponding to a 0.2 molar ratio of (S)-1·(R)-2.
- Pallavicini, Marco,Bolchi, Cristiano,Moroni, Barbara,Valoti, Ermanno,Piccolo, Oreste
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- Practical resolution of 1-phenyl-2-(4-methylphenyl)ethylamine using a single resolving agent controlled by the dielectric constant of the solvent
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A practical resolution of 1-phenyl-2-(4-methylphenyl)ethylamine 1 for obtaining (R)- and (S)-enantiomers by a dielectrically controlled resolution (DCR) method using a single resolving agent, (S)-mandelic acid 2, has been studied. The configuration of the excess enantiomer 1 in the less-soluble diastereomeric salt was found to vary depending on the solvent controlled by adjusting the solvent dielectric constant ε and the water content of the alcohol solvent. It was found that the presence of water molecules and the solvent molecular structures was key to controlling the configurational change phenomenon in the chiral discrimination between molecules 1 and 2. Moreover, the reaction environment controlled by the solvent dielectric constant plays a very distinct role in utilizing water molecules for crystallizing the less-soluble diastereomeric salt during the resolution. Based on the results, a practical resolution process for (R)-1 and (S)-1 production has been developed involving a simple solvent switch method; the (S)-1?(S)-2?H2O salt (33% yield, 96% de, E 64%) was obtained by the crystallization from 74% (w/w) aqueous ethanol in the first resolution, while the (R)-1?(S)-2 salt (23% yield, 98% de, E 46%) was crystallized from 100% ethanol of the condensate of the mother liquor after the first resolution.
- Sakai, Kenichi,Sakurai, Rumiko,Nohira, Hiroyuki,Tanaka, Rumiko,Hirayama, Noriaki
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- PROCESS FOR PREPARING HYDROCINNAMIC ALDEHYDES IN ENANTIOPURE OR ENANTIOMERICALLY ENRICHED FORM
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A process is described for preparing hydrocinnamic aldehydes in enantiopure or enantiomerically enriched form of Formula I, in which R is isopropyl or tert-butyl and R' is hydrogen, or R and R' when taken together are a methylenedioxolyl group, comprising the following steps: a) reacting the hydrocinnamic aldehyde of Formula I with the alcohol of Formula Il in enantiopure or enantiomerically enriched form to give the crystallized hemiacetal of Formula III, in which R, R' have the same meaning as Formula I and (*) indicates a stereogenic centre in the absence of a solvent or in one or more aprotic solvents or mixtures thereof with apolar solvents; b) recovering the hydrocinnamic aldehyde of Formula I in enantiopure or enantiomerically enriched form from the crystallized hemiacetal of Formula III and the aldehyde of opposite configuration in enantiopure or enantiomerically enriched form from the hemiacetal crystallization mother liquors. The invention also concerns a process for preparing the alcohol of Formula Il to be introduced into step a).
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Page/Page column 26-27
(2010/12/17)
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- COMPOSITIONS AND METHODS FOR CYCLOFRUCTANS AS SEPARATION AGENTS
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The present invention relates to derivatized cyclofructan compounds, compositions comprising derivatized cyclofructan compounds, and methods of using compositions comprising derivatized cyclofructan compounds for chromatographic separations of chemical species, including enantiomers. Said compositions may comprise a solid support and/or polymers comprising derivatized cyclofructan compounds.
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Page/Page column 45-49; 63
(2010/12/31)
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- Synthesis of enantiomerically pure amino-substituted fused bicyclic rings
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This invention describes various processes for synthesis and resolution of racemic amino-substituted fused bicyclic ring systems. One process utilizes selective hydrogenation of an amino-substituted fused bicyclic aromatic ring system. An alternative process prepares the racemic amino-substituted fused bicyclic ring system via nitrosation. In addition, the present invention describes the enzymatic resolution of a racemic mixture to produce the (R)- and (S)-forms of amino-substituted fused bicyclic rings as well as a racemization process to recycle the unpreferred enantioner. Further provided by this invention is an asymmetric synthesis of the (R)- or (S)-enantiomer of primary amino-substituted fused bicyclic ring systems.
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- ASYMMETRIC REDUCTION OF OXIME ETHERS. DISTINCTION OF ANTI AND SYN ISOMERS LEADING TO ENANTIOMERIC AMINES.
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Anti and syn ketoxime ethers were reduced with a chiral reducing agent prepared from (-)-norephedrine and 2 eq of BH3 to give S and R amines respectively in up to 92percentee.The preferred absolute configuration of the amine was dependent on the geometry of the oxime ether.
- Sakito, Yoji,Yoneyoshi, Yukio,Suzukamo, Gohfu
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p. 223 - 224
(2007/10/02)
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