Synthesis of Hexane-Tetrols and -Triols with Fixed Hydroxyl Group Positions and Stereochemistry from Methyl Glycosides over Supported Metal Catalysts

Abstract

Carbohydrates are a renewable feedstock for the production of partially reduced polyols, but typical hydrogenolysis processes are unselective toward C−O bond cleavage at different positions and erase the stereocenters present in the feedstock. In this study, we demonstrate the synthesis of new types of acyclic polyols from methyl glycosides with fixed hydroxyl group positions and stereochemistry. Products include (2R,3S)-1,2,3,6-hexanetetrol, (2R,5S)-1,2,5,6-hexanetetrol, (2S,5S)-1,2,5-hexanetriol, and (4R,5S)-1,4,5-hexanetriol. Methyl glycosides are first selectively deoxydehydrated and hydrogenated to methyl dideoxyglycosides as reported in previous work. These methyl dideoxy-glycosides are then converted to hexane-triols and-tetrols over Pt-based catalysts in water in 80−95% yield via methoxy bond hydrolysis and hydrogenation. This route largely preserves the stereocenters of the remaining hydroxyl groups (>92% stereopurity). The nature of the intermediates formed depends on the structure of the glycoside feedstock. 3,4-Dideoxy-glycosides can undergo inversion of the C 2 −OH stereocenter because of an aldose-ketose isomerization reaction, which can be mitigated by using a bifunctional metal−acid catalyst to facilitate the reaction at lower temperature. By demonstrating a new route to produce renewable polyols with fixed hydroxyl group positions and stereochemistry, this report lays the groundwork for further research into the applications of these molecules in the chemical industry.

Mechanistic Insights into the Conversion of Biorenewable Levoglucosanol to Dideoxysugars

“…Therefore, the ( S , S )/( S , R ) ratio of tetrol can be tuned through selection of the feedstock TL/EL ratio, catalyst, and temperature, which together determine whether DDM/DDG or DDF are formed during the reaction. We note that the findings in this work concerning the interplay between acid-catalyzed hydrolysis, water-assisted tautomerization, and aldose–ketose isomerization facilitated by background concentrations of OH – are likely relevant to the transformations of other deoxy sugars …”

Reduction of sugar derivatives to valuable chemicals: utilization of asymmetric carbons

“…It was demonstrated that high yields of the target chiral polyols (82-97%) were obtained while maintaining the original chiral structures (92 ≥ 99% ee). 37,39 In addition, they also reported that ReO x -Au/CeO 2 acted as an effective heterogeneous catalyst for the DODH of methyl Scheme 26 DODH of D-glucarate-6,3-lactone with ReO x /ZrO 2 catalyst and stepwise synthesis of dibutyl adipate from D-glucarate-6,3-lactone ReO x /ZrO 2 and Pd/C catalysts. 35 Scheme 27 Transformation of tartaric acid with MoO x /carbon black and HBr.…”

“…Scheme 30 Transformation of methyl glycosides to the corresponding chiral polyols by DODH, HG, hydrolysis and HG with ReO x -Pd/CeO 2 and hydrogenation catalysts 37,39. Scheme 31 DODH reaction of methyl glycosides with the ReO x -Au/ CeO 2 catalyst 40.…”

Production of Hexane-1,2,5,6-tetrol from Biorenewable Levoglucosanol over Pt-WOx/TiO2

“…1−9 Sugar derivatives have been shown to offer many opportunities to obtain such platform molecules. 10,11 Levoglucosenone (LGO) is a biobased sugar-like compound, which can be produced from cellulose by mild pyrolysis. 12−14 Notably, based on the pyrolytic method developed by the Circa Group, an actual 1000 ton LGO/year plant is currently being developed in France.…”

“…Channeling the production of commodity chemicals from petroleum-derived resources to renewable lignocellulosic feedstocks is a great route to the effective transitioning of the chemical industry toward materials and products with a lower CO 2 footprint. Biomass-derived monomers can be used as important platform molecules for the synthesis of polymers, resins, solvents, surfactants, among others. − Sugar derivatives have been shown to offer many opportunities to obtain such platform molecules. , Levoglucosenone (LGO) is a biobased sugar-like compound, which can be produced from cellulose by mild pyrolysis. − Notably, based on the pyrolytic method developed by the Circa Group, an actual 1000 ton LGO/year plant is currently being developed in France . LGO can also be produced at yields up to 51% using polar aprotic solvents and sulfuric acid at 170–230 °C .…”