Imaging Study by Mass Spectrometry of the Spatial Variation of Cellulose and Hemicellulose Structures in Corn Stalks.

The study used mass spectrometry imaging (MSI) to map the distribution of enzymatically degraded cell wall polysaccharides in maize stems for two genotypes and at several stages of development. The context was the production of biofuels, and the overall objective was to better describe the structural determinants of recalcitrance of grasses in bioconversion. The selected genotypes showed contrasting characteristics in bioconversion assays as well as in their lignin deposition pattern. We compared the pattern of cell wall polysaccharide degradation observed by MSI following the enzymatic degradation of tissues with that of lignin deposition. Several enzymes targeting the main families of wall polysaccharides were used. In the early stages of development, cellulose and mixed-linked ß-glucans appeared as the main polysaccharides degraded from the walls, while heteroxylan products were barely detected, suggesting subsequent deposition of heteroxylans in the walls. At all stages and for both genotypes, enzymatic degradation occurred preferentially in nonlignified walls for all structural families of polysaccharides studied here. However, our results showed heterogeneity in the distribution of heteroxylan products according to their chemical structure: arabinosylated products were mostly represented in the pith center, while glucuronylated products were found at the pith periphery. The conclusions of our work are in agreement with those of previous studies. The MSI approach presented here is unique and attractive for addressing the histological and biochemical aspects of biomass recalcitrance to conversion, as it allows for a simultaneous interpretation of cell wall degradation and lignification patterns at the scale of an entire stem section.

Synthesis of 1,2-cis-2-C-branched aryl-C-glucosides via desulfurization of carbohydrate based hemithioacetals.

1-C and 2-C-branched carbohydrates are present as substructures in a number of biologically important compounds. Although the synthesis of such carbohydrate derivatives is extensively studied, the synthesis of 1,2-cis-2-C-branched C-, S-, and N-glycosides is less explored. In this article a synthetic strategy for the synthesis of 1,2-cis-2-C-branched-aryl-C-glucosides is reported via a hydrogenolytic desulfurization of suitably orientated carbohydrate based hemithioacetals. 1,2-cis-2-Hydroxymethyl and 2-carbaldehyde of aryl-C-glucosides have been synthesized using the current strategy in very good yields. The 2-carbaldehyde-aryl-C-glucosides have been identified as suitable substrates for the stereospecific preparation of 2,3-unsaturated-aryl-C-glycosides (Ferrier products).

Prop-2-yn-1-yl 4,6-di-O-acetyl-2,3-dide-oxy-α-d-erythro-hex-2-enopyran-o-side.

The absolute structure of the title compound, C(13)H(16)O(6), was determined. The pyranosyl ring adopting an envelope conformation. The acetyl groups are located in equatorial positions. The crystal structure features weak C-H⋯O inter-actions.

NaHSO(4) supported on silica gel: an alternative catalyst for Ferrier rearrangement of glycals.

NaHSO(4) supported on silica gel catalyses the Ferrier rearrangement reaction of 3,4,6-tri-O-acetyl-D-glucal with alcohols and thiols to give the corresponding 2,3-unsaturated glycosides in high anomeric selectivity and good to excellent yield in short reaction time.

Phenyl 4,6-di-O-acetyl-2,3-dide-oxy-1-thio-α-d-erythro-hex-2-enopyran-oside.

The pyranosyl ring in the title compound, C(16)H(18)O(5)S, adopts an envelope conformation, with the acetyl groups in equatorial positions. In the crystal, weak C-H⋯O inter-actions link the molecules into chains.