Stereospecific molybdic acid-catalyzed isomerization of 2-hexuloses to branched-chain aldoses

1-Deoxy-d-xylulose: Synthesis Based on Molybdate-Catalyzed Rearrangement of a Branched-Chain Aldotetrose

“…The remarkable transformation of 9 into 2 is believed to involve the formation of dimolybdate complexes I and II having structures shown in Scheme . Similar complexes were originally proposed in molybdate-catalyzed C2-epimerization of aldoses in which C1 and C2 are transposed via C2−C3 bond cleavage, and more recently in the molybdate-catalyzed conversion of 2- C -(hydroxymethyl)aldopentoses to 2-ketohexoses . An inspection of these proposed complexes reveals that the aldehydic hydrogen in aldose−dimolybdate complexes can be replaced by CH 3 without introducing unfavorable steric crowding in this region of the complexes (see Scheme ), thus explaining the facile interconversion of 9 and 2 via analogous C2−C3 bond cleavage and transposition.…”

“…Subsequent NMR and crystallographic studies of molybdate complexed with acyclic alditols confirmed the structure of this species. It was observed recently that the aldehydic proton of an acyclic aldose could be replaced by a CH 2 OH group, thereby promoting interconversion between a C2 branched-chain aldose and a 2-ketose . It thus became evident that the synthesis of 2 might be effected through a similar transformation.…”

Uncharted Pathways for CrCl3 Catalyzed Glucose Conversion in Aqueous Solution

“…Hamamelose was obtained from Carbosynth. In order to detect 2-C-(hydroxymethyl) lyxose signals, sorbose was reacted with 0.2% (w/v) ammonium heptamolybdate tetrahydrate for 2 hours at 80 ºC and observed NMR signals of 2-C-(hydroxymethyl)-L-lyxose signals were identified in the resultant mixture using previously assigned chemicals shifts for the purified compound[34].…”

Enhancing tungsten oxide/SBA-15 catalysts for hydrolysis of cellobiose through doping ZrO2

“…Its yield was 4% at 15 min, and decreased as the reaction time increases, which indicated that the glucopyranosyl-glucitol formed in the primary reaction could subject to further hydrolysis. It is interesting to note that the mannose yield on these tungstate rich catalysts is significantly higher than those on the Brønsted acid type catalysts, but is similar to those on the supported molybdate catalysts [54,55]. It has been reported that molybdate dimmer could adsorb glucose through interaction with the hydroxyl groups connecting to C1-C4 carbon atoms and facilitate the forming C1 C3 bond at the expense of breaking the C2 C3 bond, leading to the formation of mannose [56].…”