• Title/Summary/Keyword: chiral intermediates

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Improving Catalytic Efficiency and Changing Substrate Spectrum for Asymmetric Biocatalytic Reductive Amination

  • Jiang, Wei;Wang, Yali
    • Journal of Microbiology and Biotechnology
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    • v.30 no.1
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    • pp.146-154
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    • 2020
  • With the advantages of biocatalytic method, enzymes have been excavated for the synthesis of chiral amino acids by the reductive amination of ketones, offering a promising way of producing pharmaceutical intermediates. In this work, a robust phenylalanine dehydrogenase (PheDH) with wide substrate spectrum and high catalytic efficiency was constructed through rational design and active-site-targeted, site-specific mutagenesis by using the parent enzyme from Bacillus halodurans. Active sites with bonding substrate and amino acid residues surrounding the substrate binding pocket, 49L-50G-51G, 74M,77K, 122G-123T-124D-125M, 275N, 305L and 308V of the PheDH, were identified. Noticeably, the new mutant PheDH (E113D-N276L) showed approximately 6.06-fold increment of kcat/Km in the oxidative deamination and more than 1.58-fold in the reductive amination compared to that of the wide type. Meanwhile, the PheDHs exhibit high capacity of accepting benzylic and aliphatic ketone substrates. The broad specificity, high catalytic efficiency and selectivity, along with excellent thermal stability, render these broad-spectrum enzymes ideal targets for further development with potential diagnostic reagent and pharmaceutical compounds applications.

Asymmetric Intramolecular Diels-Alder Cycloadditions of 2-Pyrone-3-Carboxylates and Synthesis of Vitamin $D_3$ A Ring Phosphine Oxide

  • 조천규;Gary H. Posner
    • Bulletin of the Korean Chemical Society
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    • v.19 no.9
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    • pp.957-961
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    • 1998
  • Intramolecular Diels-Alder cycloadditions of 2-pyrone-3-carboxylates with trans-vinyl silaketal groups tethered via a chiral, non-racemic 1,3-butanediol auxiliary proceeded in unexpected stepwise cycloadditions through ionic intermediates to provide cis-disubstituted bicylolactones. The ratio of two isomers, exo and endo, was 5 to 1, and each isomer was found to be diastereomerically pure (>99% de). Their relative and absolute stereochemistries were determined by $^1H$ NMR spectroscopy and confirmed by X-ray crystallography of minor, endo-adduct 9. The major exo-adduct was successfully transformed to (-)-2-butyl substituted A-ring phophine oxide 16, a key element for the synthesis of 2-butyl vitamin D3.

Synthetic Studies on Phospholipid Derivatives 1. Comparative Syntheses of (R)-and (S)-Glycerol Acetonide (Phospholipid 유도체에 관한 연구 1. (R)-과 (S)-Glycerol acetonide의 효과적인 비교합성)

  • Sung Ki Chung;B. E. Kim;K. S. Chang
    • Journal of the Korean Chemical Society
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    • v.35 no.3
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    • pp.253-257
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    • 1991
  • The optically active glycerol acetonides are often used as important chiral intermediates for many syntheses. In connection with the development of inhibitors of phospholipases, we have compared the synthetic routes to (S)-and (R)-glycerol acetonide from D-mannitol and D-isoascorbic acid, and L-serine and L-ascorbic acid, respectively. In our hands, the conversions of L-serine to (R)-glycerol acetonide and of D-mannitol to (S)-glycerol acetonide were found to be most effective.

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Recent Developments and Prospects in the Enzymatic Acylations (효소를 이용한 아실화 반응의 최근 동향과 전망)

  • Park, Oh-Jin
    • Korean Chemical Engineering Research
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    • v.51 no.6
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    • pp.716-726
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    • 2013
  • Enzymatic acylations catalyzed by hydrolytic enzymes, along with enzymatic hydrolysis, are established reactions in the synthesis of fine chemicals such as chiral intermediates and polymerizations in the industry. Those reactions have been carried out mostly in organic media due to the thermodynamic limitations. Recently, there have been reports on enzymatic acylations in aqueous media. They have dealt with the elucidation of reaction mechanisms of hydrolases and acyl transferases based on their X-ray structures, homology comparison of the two kinds of enzymes, substrate engineering of acyl donors and computational design of acyl transferases for enzymatic acylations in aqueous media. Enzymatic acylations play an important role in the combinatorial synthesis of natural products such as polyketides and nonribosomal peptides. In this review, the historic developments of enzymatic acylations and industrial examples are described briefly. In addition, recent developments of enzymatic acylations in the modification of natural products and their prospects will be discussed.