Alditols, acetyl deriv

Alditols [405] and amino sugars [406] have been analysed by GC—MS as combined methyl ether—acetyl derivatives. Acetylation was performed with acetic anhydride in pyridine, as follows. A 0.15-ml volume of re-distilled dry pyridine was added to 0.5 ml of 1.5 A acidic methanolysate containing 0.025—2.5 pmol of amino sugars. The apparent pH of the methanolic pyridinium hydrochloride varied in the range 4—5. Acetic anhydride (0.1 ml) was added and the mixture was stirred thoroughly and allowed to stand at room temperature for 30 min. Evaporation to dryness was performed in vacuum over solid KOH with subsequent vacuum drying for 4 h over P20s. SE-30 was used as the stationary phase. 

Analysis of the monosaccharide signals in the C-NMR spectrum (103.1, 77.9, 75.0, 71.3 and 66.9) and further assignment of all proton and carbon chemical shifts using H- H COSY and HMQC experiments indicated the presence of a xylose residue. The presence of xylose was confirmed by acid hydrolysis of 44 with aqueous 2N trifluoroacetic acid followed by GC analysis of the corresponding peracetylated alditol. The D-configuration was determined by GC analysis of the l-[(S)-A-acetyl-(2-hydroxypropylamino)]-l-deoxy alditol acetate derivative as for... 

The unusual sugars such as apiose, aceric acid, or KDO require special techniques for their detection and characterization. However, 0-methylated sugars can be characterized by GLC-MS of their alditol acetates (Darvill et al., 1978). Mono-O-methylated derivatives elute faster than their completely acetylated homologues. This can be illustrated by comparison of the retention times (on a SP-1000 glass capillary column) of the acetylated derivatives of xylitol (R-0.71) and 4-0-methylxylitol (R-... 

With disaccharides containing a 2-amino-2-deoxyaldose reducing residue, it is advantageous to use the A-acetyl derivative, ° or perhaps better still, the A-acetyl derivative of the disaccharide alditol. The oxidation products formed from these derivatives do not become significantly overoxidized, and hence, the stoichiometry of the reaction is clearly indicative of the linkage position. For example, 1 mol of... 

I. K. Baird, M. I. Holroyde, and D. C. Ellwood, Analysis of the products of Smith degradation of polysaccharides by g.l.c. of the acetylated, derived aldononitries and alditols, Carbohydr. 

The substitution of sodium acetate or N-methyl-imldazole for pyridine in the preparation of alditol acetate derivatives for the capillary g.c. analysis of neutral and amino-sugars using selected ion monitoring m.s. detection has been examined. While N-methyl-imidazole effected full acetylation of alditols in the presence of borates and water, it led to a higher detector background than the more tedious use of sodium acetate. Muramic acid produced two alditol acetate derivatives, the lactams (1) and (2), in a reproduceable fashion only in the sodium acetate-catalyzed procedure... 

Acetylated derivatives have been used in the characterization of dialdose dianhydrides, partially methylated heptitols, and aldobiuronic acid methyl ester methyl glycosides. The origin of the fragments with even mass numbers derived from alditol acetates is based on elimination of keten, acetic acid, and acetic anhydride. ... 

Hudson has suggested conversion of alditols to the fully acetylated derivatives which in every known instance have pronounced rotations in chloroform when the configurations are not meso (64). 

Improved procedures for the preparation and g.c. analysis of peracetylated aldoses have been developed. Acetylation (AcjO-l-raethylimidazole) can be performed directly on acid hydrolysates, and factors influencing the ratios of isomers produced have been studied. This method was compared with the alditol acetate procedure for the quantitative analysis of four plant materials. G.l.c.-m.s. data have been reported for partially methylated and acetylated derivatives of L-gfycero-n-manno- and n-gfycero-D-manno-heptoses and -heptitols. ... 

A new method for preparing alditol acetate derivatives has been detailed which avoids the need to remove borate prior to acetylation,... 

The contribution to the c.d. of pair interaction between acetyl groups in acetyl derivatives of 1,5-anhydro-alditols accounts for the observed signal, and allows their stereochemistry to be deducedf 1.3 Branched-Chain Alditols.- Doubly branched alditols (19) have been prepared (as sections of erythronolide B) by cuprous cyanide... 

Oxidation of PI with chromium trioxide. Fraction PI was twice acetylated as described above. The peracetylated polysaccharide (75 mg), together with 20 mg of mannitol hexacetate as internal standard was dissolved in 1.5 mL of HCCI3, and treated with 1.89 mL of glacial acetic acid and 189 mg of chromium trioxide, at 50°C. Aliquots were removed at zero, 30, 60 and 120 min, water then added, and the material recovered by extraction with chloroform, hydrolyzed and analysed by GLC of derived alditol acetates. 

Intramolecular cyclization can also be effected with acyclic intermediates derived from such readily available alditols as D-mannitol. Kuszmann and Vargha63 reported the formation of 2,5-anhydro-l,6-dibromo-l,6-dideoxy-4-0-(methylsulfonyl)-D-glucitol (63), in 73% yield, by boiling 3,5-di-0-acetyl-l,6-dibromo-l,6-dideoxy-2,4-di-0-... 

It so happens that the great majority of compounds separated as acetates are alditols or other polyhydric compounds, and this Section is therefore concerned with the problems of reduction and acetylation. There is no a priori reason why alditols and other polyols should not be separated as their trimethylsilyl ethers, and such methods are known (see Section VII,l,p. 57 Section XIII, p. 90 Table Va, p. 119 and Table Xlla, p. 151), but experience shows that the resolution of acyclic O-trimethylsilyl derivatives is less satisfactory than that of cyclic compounds. 

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