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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 61, Number 5
JKCSEZ 61(5)
October 20, 2017 

Asymmetric Reduction of 3-Ketoproline Ethyl Ester by Modified Borohydrides and Various Vegetables
Agustono Wibowo, Zurina Shaameri, Mohd Fazli Mohammat, Ahmad Sazali Hamzah*
Ketoproline, Stereoselective reduction, Vegetable, Sodium borohydride, Metal salt
Reduction of (±)-3-ketoproline ethyl ester (1) by NaBH4 in the presence of CaCl2 and MgCl2 as the chelating agents gave selective products cis-3(R/S)-alcohols, while reduction by NaBH4 alone or chelated with NiCl2 and AlBr3 gave mixtures of cis- and trans-alcohols. The reduction of (±)-1 by various vegetables however, gave exclusively the cis-alcohol as the major and trans-alcohol as the minor. On the contrary, reduction of (±)-1 by carrot afforded a mixture of cis- and transalcohols, in which the trans-alcohol exists as the major product. In addition, we found that this biocatalyst selectively converted S-enantiomer of (±)-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.
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