Glycosyl azides reduction

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-... 

Reduction of a-Glycosyl Azide and Peptide Coupling /V -Fmoc-Asn[tetra-0-Bzl-a-D-Glc-(1 6)-tri-0-Piv- J-D-Glc-(l—>6)-tri-0-Bzl-a-D-Glc-(l—d-AJ-Pro-OtBu 4081... 

Fig. 11. Synthesis of glycosyl amine by reduction of glycosyl azide (88,95).

The use of Pd/C (87,89), neutral Raney Ni (W-2) (91,95), and Lyndlar s catalyst (90) have been reported in literature. Conditions used for the reduction of glycosyl azide have to be carefully optimized in order to suppress anomerization and the formation of undesired a-glycosides. Use of basic conditions and procedures that avoid noble metals leads to decreased a-glycosides formation (94). 

The key [4+2] glycosylation followed by desilylation of the two phosphorylation sites resulted in a moderate 39% yield over two steps (Scheme 13.23). Phosphoramidite 153 was used to phosphorylate both of the resulting free hydroxy groups. A three-step protocol was applied for final deprotection, starting with azide reduction with Zn and acetic acid, then removal of cyanoethoxy phosphate protection with DBU, and finally... 

Scheme 1 (a) Synthesis of glycosyl azide, (b) Reduction of glycosyl azide to the corresponding glycosylamine followed... 

Reduction of protected glycosyl azides under mild conditions (hydrogenation at atmospheric pressure and room temperature using Pt02 or Raney... 

P. Boullanger, V. Maunier, and D. Lafont, Syntheses of amphiphilic glycosylamides from glycosyl azides without transient reduction to glycosylamines, Carbohydr. Res., 324 (2000) 97-106. 

Thiem et al. have described [75,76] the synthesis of hexopyranosyl imides of gluco and manno configuration starting from 0-protected glycosylamines available by reduction of glycosyl azides. Reaction of 52, 53 with succinic anhydride followed by a cycHzation reaction of the corresponding... 

Figure 2. /V-linked glycopeptides can be obtained by acylation of glycosyl amines, prepared either by reduction of glycosyl azides or directly from reducing sugars.

Glycosylamines. — a-D-Mannopyranosylamine was synthesized by reduction (H2 - Adams cat.) of the corresponding glycosyl azide (see this Chap., Section 2). A, A(-Di-(P-D-... 

Glycosyl azides are an important family of carbohydrate derivatives. They have been used as precursors of glycopeptides and heterocyclic M-glycosides. The corresponding glycosylamines, which can be obtained by reduction of the azide group, can be used as precursors to glycopolymers or hyper-branched dendrimers, after A-acryloylation. Furthermore, azide functionalities can be easily converted into... 

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