Attempted Synthesis of Type-A Inositolphosphoglycan Mediators – Synthesis of a Pseudohexasaccharide Precursor

Abstract

A block synthesis approach to the inositol‐containing pseudohexasaccharide 1 is presented. The myo‐inositol building block 6 has been prepared using a key regioselective acylation through a boron‐tin exchange reaction and the 2‐azido‐2‐deoxy glycosyl donors 15 and 17 have been synthesized from D‐glucosamine using a diazo transfer reaction. The anomeric position of the mono‐ and disaccharide building blocks has been temporarily protected as phenyl thioglycoside and this function was then converted into the different leaving groups to perform the glycosylation reactions. Both trichloroacetimidates and fluorides have been used as glycosyl donors for the construction of the different glycosidic linkages. The protected pseudohexasaccharides 44, 48‐50, which are precursors of pseudohexasaccharide 1, have been efficiently prepared and fully characterized. Pseudohexasaccharide 1 contains the fundamental structural features which have been proposed for type A inositolphosphoglycans, which may be involved in the insulin‐signaling process.

Strong Aphicidal Activity of GlcNAc(β1→4)Glc Disaccharides: Synthesis, Physiological Effects, and Chitinase Inhibition

“…In our first approach, we used an azido precursor of the glucosamine unit due to its stability and its easy conversion into a NHAc group in the last steps of the synthesis. When using thioglucoside 9 12 as a donor, standard conditions of N ‐iodosuccinimide/trifluoromethanesulfonic acid or silver trifluoromethanesulfonate (AgOTf) were ineffective for coupling, but the system13, 14 of BSP/DTBMP/trifluoromethanesulfonic anhydride (Tf 2 O) was successful to give the corresponding disaccharide in 67 % yield as a 1:2 α/β mixture, from which the major disaccharide 10 was obtained in pure form (Scheme ). In the 1 H NMR spectrum of 10 , the resonance of H1′ at δ =4.66 ppm (d, J 1′,2′= 7.9 Hz) confirmed the formation of the β‐linkage.…”

Recent trends in the synthesis of O-glycosides of 2-amino-2-deoxysugars

“…Deprotection of the phthaloyl group can be achieved with hydrazine hydrate in MeOH or EtOH, 370,371,388,430 alcoholic methylamine, 431,432 ethylenediamine in BuOH or EtOH, 368,376,380,[433][434][435] ammonia in MeOH, 398 sodium borohydride, 401,436 and hydrazine acetate, 437 to form a free amine.…”

Synthesis of a Potentially Insulin-Mimetic, Lipid-Linked Inositol Glycan

“…Scheme 3b, however, was successful, probably due to the higher stability of the phenyl thioglycoside group. 86 Chromatographic separation of the two anomers using a EtOAc/heptane solvent system (as reported in the literature) 35 was not very efficient. The spots for the starting material 24 and products were observed at the same R f on TLC using this solvent system.…”

“…The trichloroacetimidate donor 24 is also a known compound that could be synthesized from commercially available D-glucosamine 36 as shown in Scheme 3b. 86,87 An alternate strategy for synthesis of 24 was also proposed in Scheme 3a.…”

“…Rotation followed by C-O bond formation 53,82,86,87 Initial attempts to synthesize 24 via Scheme 3a were unsuccessful probably due to the interconversion between the cyclic and acyclic forms of the glucosamine derivative ( Figure 18). Due to this interconversion, benzylation of 38 resulted in a mixture of various benzylated products.…”