20246-26-8Relevant articles and documents
Phenolic compounds from the leaves of Cornus controversa
Lee, Dongho,Kang, Shin-Jung,Lee, Seung-Ho,Ro, Jaiseup,Lee, Kyongsoon,Kinghorn, A. Douglas
, p. 405 - 407 (2000)
Two novel phenolic compounds from the leaves of Cornus controversa (Cornaceae) were characterized as (-)-2,3-digalloyl-4(E)-caffeoyl-L-threonic acid and (-)-2-galloyl-4-(E)-caffeoyl-L-threonic acid, using spectroscopic methods. (C) 2000 Elsevier Science Ltd.
Oxidation of threose-series, pentose and hexoses by N-arylbromosulphonamides in alkaline medium
Shashikala,Rangappa
, p. 1907 - 1914 (2007/10/03)
Kinetic studies of the oxidation of D-galactose, L-sorbose and D-xylose by bromamine-T (sodium-N-bromo-p-toluenesulphonamide or BAT) and bromamine-B (sodium-N-bromobenzene sulphonamide or BAB) in alkaline medium has been investigated at 303 K. The rate of the reaction is first order both with respect to oxidant and 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 the decrease in dielectric constant of the medium and values of dAB, the size of activated complex are calculated. Proton inventory studies in H2O · D2O mixtures suggest a single transition state. Product analysis for D-galactose, L-sorbose and D-xylose reveal that hexoses give mainly mixture of lyxonic and threonic acids with minor proportions of hexonic, xylonic and glyceric acids, whereas xylose yields a mixture of lyxonic, threonic and glyceric acids with minor amounts of xylonic and hexonic acids. From the results of kinetic studies, reaction stoichiometry and product analysis, a possible mechanism for the oxidation of threose-series sugars is suggested.
Sodium N-Chlorobenzenesulfonamide as a Selective Oxidant for Hexosamines in Alkaline Medium: A Kinetic and Mechanistic Study
Rangappa, Kanchugarakoppal S.,Raghavendra, Manikanahally P.,Mahadevappa, Dandinasivara S.,Channegowda, Doddegowda
, p. 531 - 536 (2007/10/03)
Oxidation of D-mannosamine (1), D-glucosamine (2), and D-galctosamine (3) by sodium N-chlorobenzenesulfonamide or chloramine-B (CAB) at 313 K is followed by a shortening of carbon chain and obeys the rate law, rate = k[CAB][sugar][HO-]x, where x is less than unity. The products are arabinonic acid, ribonic acid, and erythronic acid for 1 and 2 with smaller amounts of glyceric and hexonic acids, while lyxonic and threonic acids are predominant in the oxidation of 3 with smaller amounts of glyceric and hexonic acids. Proton inventory studies made in a H2)O-D2)O mixture point toward a single transition state. In the proposed mechanism the alkoxy anion (S-) of the hexosamine formed in a base-catalyzed reaction at C-1 carbon is subjected to an electrophilic rate-limiting attack by Cl+ of the oxidant. The hexonic acid formed is decarboxylated with loss of ammonia to form the respective pentose, which is further converted into the corresponding pentonic acid. The breaking of the bond between C-1 and C-2 carbons in pentose yields tetronic acids. The thermodynamic parameters for sugar alkoxy anion formation and activation parameters for the rate-limiting step have been evaluated.
