Azido carbohydrates

The latter sequence, as reported by Overkleeft, van Boom and coworkers, employs substrates of type 9-42 containing both azide and aldehyde functionalities. Treatment of 9-42 with PMe3 in MeOH at room temperature forms a cyclic imine 9-43 via an intermediate phosphazene. Following the addition of an acid and an isocyanide 9-43, products of type 9-44 are obtained. According to this scheme, enan-tiopure carbohydrate-derived azido aldehydes 9-45 and 9-48 led to the morpholino compounds 9-46 and 9-47, as well as to the pipecolic acid scaffolds 9-49 and 9-50, re-... 

Figure 17.12 Azido derivatives of sugars can be used as monomers for glycan and carbohydrate synthesis by cells. Such modifications can be probed using click chemistry or Staudinger ligation reactions.

Other carbohydrate scaffolds with synthetic interest have also been investigated by NMR. For instance, the factors driving the conformational preferences of methyl azido-trideoxy-hex-5-enopyranosides have been discussed based on the analysis of the 1H-1H coupling constants which afford conformational information.61... 

A. Hasegawa, M. Goto, and M. Kiso, An unusual behavior Of methyl or benzyl 3-azido-5-0-benzoyl-3,6-dideoxy-a-L-talofuranoside with (dimethylamino) sulfur trifiuoride migration of the alkoxyl group from the C-l to the C-2 position, J. Carbohydr. Chem. 4 627 (1983). 

C. Auge, S. David, and A. Malleron, An inexpensive route to 2-azido-2-deoxy-t>-mannose fcnd its conversion into an azido analog of Af-acetylneuraminic acid, Carbohydr. Res. 188 201 (1989). 

M. Kiso, A. Yasm, and A. Hasegawa, Synthesis of 2-azido-2-deoxy-3,4 5,6-di-0-isopropyl-idene-aldehydo-D-aanoose dimethyl acetal and 4-azido-4-deoxy-2r3 5,6-di-0-isopropyI-i ene-aldehydo-D-piictoee dimethyl acetal, Carbohydr. Res. 127 137 (1984). 

M. Bols, I. Lundt, and E. R. Ottosen, Preparation of 2-, 3-, and 4-deoxy derivatives of L-rhamnose, and derivatives of 2-azido-2-deoxy-L-rhamnose and 2,6-dideoxy-2-fluoro-L-glucose, for use in glycosylation reactions, Carbohydr. Res., 222 (1991) 141-149. 

G. Yang and F. Kong, Synthesis and glycosidic coupling reaction of substituted 2,6-dioxabicyclo[3.1.1]heptanes l,3-anhydro-2-azido-4,6-di-0-benzyl-2-deoxy-/ -D-manno-pyranose, Carbohydr. Res., 312 (1998) 77-83. 

M. Kloosterman, M. P. de Nijs, and J. H. van Boom, Synthesis of l,6-anhydro-2-0-trifluoromethanesulphonyl-/l-D-mannopyranose derivatives and their conversion into the corresponding l,6-anhydro-2-azido-2-deoxy-/ -D-glucopyranoses a convenient and efficient approach, J. Carbohydr. Chem., 5 (1986) 215-233 compare Ref. 129. 

E. Ayadi, S. Czemecki, and J. Xie, Convenient preparation of perbenzylated 2-azido and 2-iV-acetylamino-2-deoxy-D-hexono-1,5-lactones by oxidation of the corresponding lactols,. /. Carbohydr. Chem., 15 (1996) 191-199. 

---