Peracetyl derivative

Reaction of hydrazine 165 with a number of monosaccharides give hydrazones 166 (92BCJ546). Their acetylations gave peracetyl derivatives 167. The same reactions were extended to the /V-methyl and the 7-methyl derivatives of 165 (93 JPROO). That compounds 166 exist as open-chain structures was based on a 2D NMR study (93MI1) (Scheme 35). 

The compositions of high-mannose oligosaccharides isolated from urine of animals suffering from genetic or chemically induced mannosidoses have been assigned from their f.a.b.-mass spectra. After chromatography, some samples were sufficiently pure to be examined underivatized. Others required conversion into their peracetylated derivatives. 

Warren and associates (18) have prepared a glycosyl azide derivative (15) of a heptasaccharide. This glycosyl azide was obtained from O-a-D-manno-pyranosyl-( 1 — 6)-0-[a-D-mannopyranosyl-( 1 — 3)-(9-a-D-mannopyrano syl-(l— 6)-0-a-D - mannopyranosyl - (1 — 3)] - O-fi- d - mannopyranosyl -(1 — 4) - O - (2 - acetamido - 2 - deoxy-/ -d-glucopyranosyl) - (1 — 4) - 2 -acetamido-2-deoxy-D-glucopyranose (12) by treatment of its peracetylated derivative 13 with trimethylsilyl trifuoromethanesulfonate, followed by reaction of the intermediary oxazoline 14 with trimethylsilyl azide. Reduction of the glycosyl azide 15 in the presence of Lindlar catalyst gave the glycosyla-mine derivative 16. The condensation of 16 with 1-tert-butyl N-(9-fluoren-... 

Sephadex LH-20 methanol peracetylated derivatives of chitin oligosaccharides 92... 

Consideration of rotatory powers of l,l-bis(acylamido)-l-deoxy-alditols showed79 certain correlations between optical rotation (d line of sodium) and configuration that can be summarized as follows. (a) When the acyl group is aliphatic (for example, acetyl or propionyl), the alditol will be dextrorotatory in water if the configuration of C-2 is S. (The rule does not apply to peracetylated derivatives.) (b) When the two substituents on C-l are benzamido and the configuration at C-2 is S, a solution of the alditol in pyridine will be levorotatory. Peracetylation does not alter applicability of this rule, (c) The abso-... 

Shapiro and Acher[136] condensed the gal-oc-( 1 -> 4)-gal derivative (124) [prepared by the action of hydrogen bromide in acetic acid on the previously described peracetyl derivative [137] with the 1,6-anhydroglucose derivative (125) [or (126) which was superior since acyl migration was reduced] to give the trisaccharide (127). This was acetolysed and converted into the glycosyl chloride and condensation of the latter with the benzoyl ceramide (63) and subsequent deprotection gave the complete Fabry glycolipid. 

In the synthesis of the glycolipid asialo GMI described by Ogawa and co-workers [107] the trisaccharide derivative (215) (used in the synthesis of asialo GM2) was converted into the 4,6-O-benzylidene derivative (233) and this was condensed with aceto-bromogalactose in the presence of mercury(II) cyanide and molecular sieves to give the P-linked acetylated galactose derivative in 97 % yield. The product was deprotected and acetylated to give the peracetyl derivative (234) of the tetrasaccharide which was converted into the free sugar (235) with hydrazine hydrate. Compound (235) was converted into asialo GMI via the imidate as described above for the synthesis of asialo GM2 from the imidate (219). 

Figure 14. Field desorption mass spectra of peracetyl derivative of N-stearoyl dihydrolactocerebro-...

A series of closely related oligosaccharides with increasing complexity and in decreasing abundance were observed on reverse-phase high pressure liquid chromatography as the peracetylated derivatives [procedure adapted from those of Wells and Lester... 

A. Dell, Preparation and desorption mass spectrometry of permethyl and peracetyl derivatives of oligosaccharide, Meth. Enzymol., 193 (1990) 647-660. 

For the experimental data, the values are given for aglycones having the Gal (28), Glc (29), and Man (30, 32) configurations, in this order. The asterisk denotes the values for the peracetylated derivative. 

Peracetylated derivatives of alditols and reduced sugars are sufficiently stable for GC analysis and possessing good properties, but a relatively complicated procedure is required for their preparation. They also cannot be applied to the simultaneous determination of the sugar and the corresponding alditol with xylose, 2- and 4-substituted isomers cannot be resolved owing to the symmetry of xylitol. This gave rise to the use of combination with other derivatives, firstly with nitriles [442]. The procedure for a standard mixture... 

The ESI/MS/MS fragmentation spectrum of permethylated LNF-II is displayed in Figure 8.48. [243] This spectrum is somewhat more complicated than the one from the per-acetylated derivative, but allows additional structural information to be obtained. As for the peracetylated derivative, this spectrum contains the ions characteristic of the sequence observed at m/z 638 (B2, trisaccharidic Hex-[Fuc]-GlcNAc-Me 8) and 842 (B3, Hex-[Fuc]-GlcNAc-Hex-Me 11), which allow the branched structure and the sequence on the reducing side to be established. 

Under these conditions, hydrolysis of peracetylated derivatives 135,136, and 139 was very slow, presumably because of the electron-withdrawing effect of the acetoxy groups. When /V-iodosuccinimide was employed instead of mercury trifluoroacetate, the reaction was complete in 12 h at room temperature and the yield was good (Table II). 

The methylacarviosin 447, a core structure of acarbose and related pseudo-oligosaccharidic a-amylase inhibitors, together with its 6-hydroxy analog 448, were prepared by Shibata et al. [257] from the corresponding oligobiosaminide derivatives 443 and 444. The aziridine intermediates 445 and 446 were treated with hydrochloric acid to give the corresponding 6 -chloro derivative, and then elimination of the chlorine by base fmnished the title compoimds 447 and 448 as peracetylated derivatives (compoimds 441-448). 

There have been no reports of bioactive metabolites from the ascidians of the cool temperate west coast of southern Africa. Bioactivity guided fractionation of an ethyl acetate extract of the marine ascidian, Pseudodistoma sp., collected in the Tsitsikamma Marine Reserve on the warm temperate south-east coast of southern Africa, revealed that the anti-microbial activity in this extract resided in a group of detergent-like acyclic amino alcohols isolated as their peracetylated derivatives 80 83... 

The mass spectra of several aromatic C-glycosyl compounds have been studied. The fragmentation patterns of these compounds are largely governed by the aromatic residue, but secondary fragmentations typical for the sugar moiety (such as eliminations of acetic acid or ketene from peracetylated derivatives) are observed. 

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