• Title/Summary/Keyword: Stereoselective synthesis

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Asymmetric Reduction of 3-Ketoproline Ethyl Ester by Modified Borohydrides and Various Vegetables

  • Wibowo, Agustono;Shaameri, Zurina;Mohammat, Mohd Fazli;Hamzah, Ahmad Sazali
    • Journal of the Korean Chemical Society
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    • v.61 no.5
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    • pp.244-250
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    • 2017

  • Reduction of (${\pm}$)-3-ketoproline ethyl ester (1) by $NaBH_4$ in the presence of $CaCl_2$ and $MgCl_2$ as the chelating agents gave selective products cis-3(R/S)-alcohols, while reduction by $NaBH_4$ alone or chelated with $NiCl_2$ and $AlBr_3$ gave mixtures of cis- and trans-alcohols. The reduction of (${\pm}$)-1 by various vegetables however, gave exclusively the cis-alcohol as the major and trans-alcohol as the minor. On the contrary, reduction of (${\pm}$)-1 by carrot afforded a mixture of cis- and trans-alcohols, in which the trans-alcohol exists as the major product. In addition, we found that this biocatalyst selectively converted S-enantiomer of (${\pm}$)-1 to the cis-alcohol, and R-enantiomer to a mixture of cis- and trans-alcohols with cis-alcohol as the major product. This fact prompted us to use various fresh plant tissues for stereoselective reduction of diverse types of pyrrolidinones, as its stereoselectivity towards racemic mixtures is higher compared to that using chemical reducing agents.

  • https://doi.org/10.5012/jkcs.2017.61.5.244 인용 PDF KSCI

Stereoselective Synthesis and Antiviral Activity of Novel 4′(α)-Hydroxymethyl and 6′(α)-Methyl Dually Branched Carbocyclic Nucleosides

  • Kim, Jin-Woo;Choi, Bo-Gil;Hong, Joon-Hee
    • Bulletin of the Korean Chemical Society
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    • v.25 no.12
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    • pp.1812-1816
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    • 2004

  • The stereoselective synthesis 4′,6′-dually branched carbocyclic nucleosides was accomplished in this study. The introduction of a methyl group in the 6′$({\alpha})$-position was accomplished by Felkin-Anh controlled alkylation. The construction of the required 4′$({\alpha})$-quaternary carbon was carried out using a [3,3]-sigmatropic rearrangement. Bis-vinyl 6 was successfully cyclized using a Grubbs' catalyst II. The natural bases (adenine, cytosine) were efficiently coupled using a Pd(0) catalyst. When the synthesized compounds were examined for their activity against several viruses such as the HIV-1, HSV-1, HSV-2 and HCMV, the cytosine analogue 13 exhibited good antiviral activity against the HCMV.

  • https://doi.org/10.5012/bkcs.2004.25.12.1812 인용 PDF KSCI

A Stereoselective Synthesis of 1 $\beta$-Aminocarbapenems.

  • Seo, Gyeong Jae;Lee, Tae Ho;Lee, Yeon Yeong
    • Bulletin of the Korean Chemical Society
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    • v.22 no.6
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    • pp.553-558
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    • 2001

  • A stereoselective synthesis of $1\beta-aminocarbapenems$ (11a-c) starting from-4-acetoxy-2-axetidinone derivative 4 is described. 4-Acetoxy-2-azetidinone derivative (4) was reacted with lithium enolate of benzophenone limine of glycine phenyl ester (5f) to give alkylated product (R)-6f in good yield with high diastereoselectivity. The alkylated procudt (R)-6f was transformed to thioesters (7a-c) by transesterification with thiols, Thioesters (7a-c) were converted to their oxalimides (8a-c), followed by the phosphite-mediated reductive cyclization to give carbapenems (9a-c). Removal of all protecting groups of carbapenems (9a-c) afforded $1\beta-aminocarbapenems$ (11a-c).

  • https://doi.org/10.5012/bkcs.2001.22.6.553 인용 PDF