Monosaccharides apiose

The glycosyl-residue compositions of the three purified fractions (Table 1) were very similar with a predominance of galacturonic acid, rhamnose and arabinose. The presence in the three purified fractions of the rare monosaccharides characteristic of RG-II (e.g. 2-( -methyl-L-fucose, 2-O-methyl-D-xylose, apiose, Kdo, Dha and aceric acid) was confirmed by GC-CIMS analysis. The molar ratios corresponded approximately to the known structure of the RG-II molecule (Figure 1) and to previously published data for RG-II from sycamore [26], rice [4], arabidospis leaves [8] and Pectinol [12]. 

Within this extremely important group of monosaccharides [9,107] the typical representative bears a branched functional group at any position except the anomeric carbon, but most commonly at the C-2 and C-3, as in natural L-streptose, D-hamamelose, or L-apiose. 

Pathways in the formation of NDP-sugars. A seiection of monosaccharide conversions occurring at the phosphate ester and nucieotide-monosaccharide ievei in animais, piants and bacteria are shown all pathways radiate from fructose-6-phosphate, indicating the central role of this metabolite. The dTDP, GDP and UDP-yV-acetylmu-ramic pathways are peculiar to bacteria, whereas ADP-o-glucose, UDP-o-apiose and UDP-L-arabinose are found in plants. For reasons of simplicity, other pathways, e. g., to UDP-L-rhamnose in plants, GDP-o-rhamnose in Pseudomonas aeroginosa and GDP-o-arabinose in trypanosomatids are not included. The figure is reproduced from Chap. 6.4 of the first edition of this book... 

The unambiguously assignment of H and resonances of each monosaccharide was made (Table 2) by using 2D NMR spectra.. Comparison of the CNMR data of 28-O-sugar moiety in compound 2 with those of the corresponding individual methyl glycosides indicated that one apiose unit and one xylose unit were at terminal positions, and that the glycosylation positions were at C-3 of inner arabinose (+12.2 ppm), C-2 of inner xylose (+5.8 ppm), C-3 and C-4 of inner rhanuiose (+11.3 and +5.0 ppm, respectively) [5, 6]. In the HMBC spectrum of... 

D-Apiose a branched monosaccharide, M, 150.13, Kd +9° (pure syrup). d-A. is found in various glyco-... 

The monosaccharides in the glycosides include o-xylose, o-glucose, o-galactose, D-aUose, D-apiose, D-fucose, o-quinovose, o-glucuronic acid, L-arabinose, and L-rhamnose. 

A hitherto unobserved component of the primary cell walls of dicotyledonous plants, rhamnogalacturonan II, has been isolated and partially characterized. It is a very complex polysaccharide containing residues of ten different monosaccharides including o-apiose, 2-O-methyl-D-xylose, and 2-O-methyl-L-fucose. The polysaccharide, which accounts for 3—4% of the primary cell walls of suspension-cultured sycamore cells, is also characterized by the presence of 2-linked D-glucosyluronic acid, 3,4-linked L-fucosyl, and 3-linked L-rhamnosyl residues. These linkages have not previously been detected in polysaccharides of sycamore primary cell walls. Evidence was also presented that similar polysaccharides are present in the primary cell walls of pea, pinto bean, and tomato. 

Another structural variation replaces a hydroxyl group with an amine group and its derivatives. A few monosaccharides have branched structures. D-Apiose, which is present in parsley and many other plants, is an example. Note that 0-3 is not a stereogenic center because it is bonded to two hydroxymethyl groups. 

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