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【答案】应助回帖
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感谢参与，应助指数 +1
greenhand_ku: 金币+2, 感谢您的及时应助，欢迎常来本版交流。 2014-05-23 08:05:20
吡啶二甲酸: 金币+50 2014-05-25 14:43:59
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The crucial part of the asymmetric addition is the design and synthesis of chiral ligand. Ephedrine and its derivatives as the common ligands play important role in asymmetric addition reactions. Due to the limited methods for the derivatization of ephedrine, there is a need to develop new class of ligand for the asymmetric addition reactions. According to the potential problems, starting from readily available enantio-enriched amino acid as the chiral pool, use 2,6-pyridine dicarboxylic acid as the substrate. After esterification, reduction followed by oxidation to form 2,6-pyridine dialdehyde whereas chiral amino acid underwent esterification, Grignard reaction to provide a series of beta- amino alcohols (1a-1f). Through the condensation reaction of 2,6-pyridine dialdehyde with beta- amino alcohols (1a-1f), the intermediates (2a-2f) were obtained, after the further reduction using NaBH(OAc)3, 6 novel pyridine containing beta- amino alcohols were successfully achieved together with an additional ligand 3g. All the novel compounds were charecterized via 1H NMR, 13C NMR as well as Infra-red spectrometry. The reaction condition optimization was also carried out, as a result, they overall reaction yield has reached 45-50%. This synthesis has set up a solid foundation for the future studies of the enantioselectivity of asymmetric addition reactions using organozinc reagents with aldehydes. |
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