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    Bio-catalytic asymmetric synthesis of ?-adrenergic receptor blocker precursor: (R)-2-bromo-1-(naphthalen-2-yl)ethanol
    (Taylor & Francis Ltd, 2020) Tasdemir, Volkan; Kalay, Erbay; Dertli, Enes; Sahin, Engin
    Aromatic alpha-halohydrins, particularly 2-haloethanols as significant precursor of drugs, can easily be converted to chiral beta-adrenergic receptor blockers. Eight strains of Lactobacillus curvatus were tested as biocatalysts for asymmetric reduction of 2-bromo-1-(naphthalen-2-yl)ethanone 1 to 2-bromo-1- (naphthalen-2-yl) ethanol 2. The parameters of the bioreduction were optimized using L. curvatus N4, the best biocatalyst found. As a result, (R)-2-bromo-1-(naphthalen-2-yl)ethanol 2, which can be beta-adrenergic receptor blocker precursor, was produced for the first time in high yield and enantiomerically pure form using biocatalysts. Moreover, the gram scale synthesis was performed and 7.54 g of (R)-2 was synthesized as enantiopure form (enantiomeric excess >99%) in 48 h. The important advantages of this process are that it produces of (R)-2 for the first time in enantiopure form, in excellent yield and under environmentally friendly and moderate reaction conditions. This system is of the potential to be applied at a commercial scale.
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    Characterisation and functional roles of a highly branched dextran produced by a bee pollen isolate Leuconostoc mesenteroides BI-20
    (Elsevier, 2022) Yilmaz, Mustafa Tahsin; Ispirli, Humeyra; Taylan, Osman; Tasdemir, Volkan; Sagdic, Osman; Dertli, Enes
    Lactic Acid Bacteria (LAB) from different niches can be responsible for the production of distinct exopoly-saccharides (EPS) that might possess important structural and technological features. In this respect, the aim of this study was to isolate an EPS producer LAB strain from bee pollen environment. Leuconostoc mesenteroides BI-20 with a slimy-mucoid colony morphology was identified from bee pollen and the structural, technological and functional characteristics of EPS produced by this strain were determined. EPS BI-20 was a highly branched dextran containing 20% (1 -> 3)-linked alpha-D-glucose branches determined by H-1 and C-13 NMR analysis. The presence of (1 -> 6)/(1 -> 3)-linked alpha-D-glucose linkages in dextran BI-20 was also confirmed by FTIR analysis. Dextran BI-20, with a molecular weight of 1 x 10(8) Da, possessed strong thermal properties, amorphous nature and highly branched and fibrous microstructural characteristics determined by DSC, TGA, XRD and SEM analysis, respectively. In terms of functional roles, dextran BI-20 demonstrated strong antioxidant capacity detected by ABTS and CUPRAC tests. Finally, no digestion was observed in dextran BI-20 under simulated gastric conditions. Results of this study unveiled techno-functional characteristics of dextran BI-20 produced by a bee pollen isolate LAB strain.