Glycosides partially acylated

Stoicheiometric RuOyCCl was also used to oxidise several furanoses, partially acylated glycosides and l,4 3,6-dianhydrohexitols [317] pyranosides to pyrano-siduloses [313] methyl 2,3,6-tri-O-benzoyl-a-D-glucopyranoside and its C-4 epimer to the a-D-xy/o-hexapyranosid-4-ulose (Table 2.3) [317], and methyl 2,3,6-trideoxy-a-D-e 7f/tro-hexapyranoside to the -a-D-,g/yceri9-hexa-pyranosid-4-ulose, an intermediate in the synthesis of forosamine [318], It was also used to oxidise benzyl 6-deoxy-2,3-0-isopropylidene-a-L-mannopyranoside to the a-L-/yxo-hexapyranosid-4-ulose [319] and for oxidation of isolated secondary alcohol functions, e.g. in the conversion of l,6-anhydro-2,3-0-isopropylidene-P-D-man-nopyranose to the-P-D-/yxo-hexa-pyranos-4-ulose mannopyranose (Fig. 2.16, Table 2.3 [20, 320, 324]). 

General Procedure for the Preparation of Partially Acylated MOP Glycosides 3-Methoxy-2-pyridyl 2,3,4-tri-O-p-fluorobenzoyl-fi-D-glucopyranoside (33)... 

Additionally, the arming and disarming properties of the STaz glycosides were evaluated. It was demonstrated that activated (benzylated) STaz derivatives could be activated over electronically disarmed (partially acylated) STaz glycosyl acceptors in die presence of either AgOTf or Cu(OTf)2 78). For example, a classic armed-disarmed approach (79) allowed chemoselective activation of 54 over disarmed acceptor 61 in the presence of Cu(OTf)2to afford... 

Fig. 4. Survey of the selected fragment ions A-H worked out for trimethylsilylated (O-acylated) N-acylneuraminic acid methyl ester(s) (methyl glycosides) and for (partially) O-methylated N,N>acetyl,methyl-neuraminic acid methyl ester methyl glycosides. Partially O-methylated compounds are trimethylsilylated or acetylated.

A partial synthesis of cerebroside sulfate [ sulfatide, the glycoside of ceramide with galactose 3-sulfate, (90)] was achieved [90] by acylating the sphingosine galactosyl 3-sulfate (89) (obtained by basic hydrolysis of natural sulfatide) with palmitoyl chloride or D-2-acetoxypalmitoyl chloride (and subsequent basic hydrolysis of the... 

Serious undesired side reactions we encountered during the attempted total synthesis of multifidoside B are described here (Scheme 21). Efforts toward the total synthesis was hampered by the final-step deprotection of the partially protected natural product precursor 48, resulting in giving decomposed product 49 by P-elimination of the glycoside moiety. Use of milder conditions for the deprotection resulted in double-bond isomerization to give an /Z (2/1) mixture of multifidoside B. It has also been reported in the literature that the undesired side reactions such as acyl migration from the desired 4-(9-acylate to the undesired 6-0-acylate and overreduction, and isomerization of the p-coumaroyl moiety have been observed during... 

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