1-azido disaccharide

M. Schamann and H. J. Schafer, TEMPO-mediated anodic oxidation of methyl glycosides and 1-methyl and 1-azido disaccharides, Eur. J. Org. Chem. (2003) 351-358. 

Methyl 0-(2-Azido-3-0-Benzyl-4,6-0-Benzylidene-2-Deoxy-a-D-Galactopyranosyl)-(l-3)-0-(2-Azido-4,6-0-Benzylidene-2-Deoxy-(3-D-Galactopyranosyl)-(l-6)-2,3,4-Tri-O-Benzyl-a-D-Clucopyranoside (112) A mixture of the disaccharide acceptor 111 (0.1 mmol),... 

Thiodisaccharides in the GlcNAc series were recently synthesized. The substitution reaction of the triflate at C-4 of 2-acetamido- and 2-azido-o- galacto-sides (34 d) and (34 e) in DMF with thiolate nucleophiles (8i) or (8j) and (30b) afforded the expected disaccharides (aroimd 50 and 68%), from which the deprotected (41) and (42) were obtained [39a, 32] (Scheme 13). The coupling of the triflate (34 f) with the thiol (8j) in DMF in the presence of cysteamine gave a 63% yield of the expected thiocfrsaccharide which was converted into (41) in high yield [39b],... 

In this respect it is interesting to note that the tandem aldolization technique proved amenable also to the synthesis of a first C-glycosidic aza sugar (Scheme 2.2.5.19) [29, 36]. A rather simple dihydroxylated azido dialdehyde was generated from racemic azidocyclohexene 60 and subjected to FruA catalysis. The latter effected a smooth tandem addition to provide a diastereoisomerically pure bispyranoid azido C-disaccharide 61, from which the pyrrolidine-type aza sugar 62 was... 

The procedure was extended to O-benzylidene derivatives of some disaccharides,116-132 2-acetamido-2-deoxyhexopyranosides, 3-azido-3-... 

Paulsen and co-workers [191] synthesised the trisaccharide (263) representing the afucosyl end group of the blood-group A (type 1) determinant from the disaccharide (264). This was acetylated and deacetonated and the product converted into the acetate (265) via the 3, 4 -orthoacetate. Condensation of (265) with the azido-chloride (237) in the presence of silver perchlorate gave the a-linked trisaccharide (266) which was deprotected to give (263). 

The 2-azido-2-deoxy derivatives of mono- and disaccharides such as 27a and 27b are versatile intermediates in the preparation of 2-amino-2-deoxysaccharides23. 

Consequently, a dihydroxylated azidodialdehyde was examined next which indeed behaved as anticipated. When generated from the racemic allylic azide 37 [109], FruA catalysis effected a smooth tandem addition to the dialdehyde to provide a diastereoisomerically pure bipyranoid azido C-disaccharide 38, from which the pyrrolidine type aza sugar 39 was highly stereoselectively produced by standard reductive amination [108]. Model considerations suggest a close resemblance of the protonated aza C-disaccharide to transition states of saccha-rase or maltase. Indeed, several of the glycosidases tested were inhibited by 39 at concentrations below 1 mM. 

The block synthesis strategy is demonstrated here by the synthesis of the dimeric-Lewis octasaccharide (29) described by Schmidt and coworkers [8,9]. As shown in the retrosynthetic analysis (Scheme 5.5), the octasaccharide (29) should be accessible from the tri- (30) and disaccharide (31) units, represented by the blocks 32 and 33. The trisaccharide block can be disconnected from the L-fucosyl (34) and D-galactosyl (35) imidates and the 2-azido-2-deoxy-o-glucose derivative (36). 

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