- Synthesis of l -Ribose from d -Ribose by a Stereoconversion through Sequential Lactonization as the Key Transformation
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l -Ribose, a key precursor of various l -nucleosides can only be synthesized from other sugars or other non-sugar precursors. Herein, the study involves the synthesis of naturally rare l -ribose from readily available d -ribose. Though, many synthetic strategies are developed to meet the increasing demands of l -ribose, seeking innovation, a synthesis employing sequential lactonization as the key transformation was explored. This novel conversion involves protection, oxidation, sequential lactonization, reduction with DIBAL-H, and deprotection..
- Ban, Jaeyoung,Shabbir, Saira,Lim, Minkyung,Lee, Byunghoon,Rhee, Hakjune
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p. 4299 - 4302
(2017/09/12)
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- Expanding the reaction space of aldolases using hydroxypyruvate as a nucleophilic substrate
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Aldolases are key biocatalysts for stereoselective C-C bond formation allowing access to polyoxygenated chiral units through direct, efficient, and sustainable synthetic processes. The aldol reaction involving unprotected hydroxypyruvate and an aldehyde offers access to valuable polyhydroxy-α-keto acids. However, this undescribed aldolisation is highly challenging, especially regarding stereoselectivity. This reaction was explored using, as biocatalysts, a collection of aldolases selected from biodiversity. Several enzymes that belong to the same pyruvate aldolase Pfam family (PF03328) were found to produce the desired hexulosonic acids from hydroxypyruvate and d-glyceraldehyde with complementary stereoselectivities. One of them was selected for the proof of concept as a biocatalytic tool to prepare five (3S,4S) aldol adducts through an eco-friendly process.
- De Berardinis, Véronique,Guérard-Hélaine, Christine,Darii, Ekaterina,Bastard, Karine,Hélaine, Virgil,Mariage, Aline,Petit, Jean-Louis,Poupard, Nicolas,Sánchez-Moreno, Israel,Stam, Mark,Gefflaut, Thierry,Salanoubat, Marcel,Lemaire, Marielle
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p. 519 - 526
(2017/08/14)
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- A novel mechanism for the oxidation of erythro-series pentoses and hexoses by N-arylbromosulphonamides in alkaline medium
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Kinetic studies of the oxidation of D-mannose, D-glucose, D-fructose, L-arabinose and D-ribose by bromamine-T (sodium N-bromo-p-toluenesulphonamide or BAT) and bromamine-B (sodium N-bromobenzenesulphonamide or BAB) in alkaline medium were investigated at 30°C. The rate of the reaction was first order both with respect to the oxidant and the sugar and second order with respect to [HO-]. The addition of the reaction product, p-toluenesulphonamide (PTS) or benzenesulphonamide (BSA), and the variation of ionic strength of the medium have no effect on the rate. The rate decreases with decrease in dielectric constant of the medium and values of dAB, the size of activated complex, were calculated. Proton inventory studies were made in H2O-D2O mixtures. The activation parameters of the reaction were computed from Arrhenius plots. HPLC and GLC-MS analysis of the products indicated that the sugars were oxidized to a mixture of aldonic acids consisting of arabinonic, ribonic, erythronic and glyceric acids. A general mechanism consistent with the observed results has been proposed.
- Shashikala,Rangappa
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p. 219 - 234
(2007/10/03)
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