C-Disaccharides synthesis

A. Baudat and P. Vogel, Aza-C-disaccharides Synthesis of 6-deoxyglalctono-jirimycin (3-C-(l->3) linked with D-altrofuranosides and D-galactose, J. Org. Chem., 62 (1997) 6252-6260. 

Martin and coworkers have used this strategy for synthesis of a- and P-(l,6)-linked C-disaccharides (Eq. 5.40).58... 

PCC in the presence of 4 A MS to afford the corresponding keto sugars (175, 176), which after Tebbe methylenation led to the corresponding exoglycals, valuable intermediates for the synthesis of C-disaccharides. Dondoni el al.159 made use of PCC in the presence of powdered 4 A MS to introduce suitable formyl groups in the carbohydrate, and allowing the synthesis of >6)-linked oligosaccharides,... 

B. Vauzeilles and P. Sinay, Selective radical synthesis of /i-C-disaccharides,... 

Anomeric acetates 104 have been also used as electrophiles toward alkynylindium reagents 105 under Barbier conditions. Good yields and 1,2-cA-stereoselectivities were observed during the reaction (Scheme 36). The alkynylation was applied to the synthesis of an a-(l —>6)-C -disaccharide (110) analogue of methyl isomaltoside.108... 

This strategy was later refined by Stork and co-workers142 who used silicon (e.g. 164) as the tethering atom [Scheme 55a)]. The latter strategy was adapted by Sinay and co-workers143 for the synthesis of C-disaccharides (e.g. 169) by employing 8- and 9-endo radical cyclizations with the readily prepared silaketal connectors [Scheme 55b)]. 

Fig. 14 Synthesis of a C-disaccharide exploiting the Sml2 catalyzed reaction of a glycosyl pyridylsulphone.

P. Vogel, S. Gerber-Lemaire and L. Juillerat-Jeanneret, Imino -C- disaccharides and analogs synthesis and biological activity, in Imino sugars, from synthesis to therapeutic applications, ed. P. Compain and O. Martin, Wiley, 2007, pp. 87-130. 

Applying the procedure just described, Rouzaud and Sinay (65) described a stereospecific synthesis of a C-disaccharide in which a methylene group takes the place of the interunit oxygen atom. Starting from 51a and the dibromoalkene 59, the hemiacetal 60 was obtained. Reduction of 60, followed by catalytic hydrogenolysis, gave the /J-(l — 6)- C-disaccharide 61. 

The reaction of type i is utilized for the preparation of a variety of dicarboxylic acids. Scheme 25 shows the synthesis of a C-disaccharide (73) from a carbohydrate carboxylic acid (72) [98]. 

H. Berber, T. Brigaud, O. Lefebvre, R. Plantier-Royon, C. Portella, Reactions of difluoroenoxysilanes with glycosyl donors Synthesis of difluoro-C-glycosides and difluoro-C-disaccharides, Chem. Eur. J. 7 (2001) 903-909. 

T.F. Herpin, W.B. Motherwell, M.J. Tozer, The synthesis of difluoromethylene-linked C-glycosides and C-disaccharides, Tetrahedron Asymmetr. 5 (1994) 2269-2282. 

Figure 6.26 Synthesis of difluoro-C-glycosides and difluoro-C-disaccharides starting from difiuoroenoxysiianes/ ...

C-Glycoside synthesis via the intermolecular addition of anomeric radicals to activated alkenes has been pioneered by Giese and co-workers [120]. A wide variety of acceptors have been used in this area and both simple [131,132] and more complex (a C-disaccharide 290) [133] examples are shown (Scheme 77). 

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... 

E. Caneva, Synthesis of C-disaccharides through dimerization of exo-glycal, J. Org. Chem. 57 1304 (1992) A. Boschetti, F. Nicotra, L. Panza, G. Russo, and L. Zucchelli, Easy synthesis of a C-disaccharide, J. Chem. Soc. Chem. Commun. p. 1085 (1989). 

D. P. Sutherlin and R. W. Armstrong, Stereoselective synthesis of dipyranyl C-disaccharides, Tetrahedron Lett. 34 4897 (1993). 

R. R, Schmidt and R. Preuss, Synthesis of carbon bridged C-disaccharides, Tetrahedron Lea. 30 3409 (1989) B. Giese, M. Hoch, C. Lamberth, and R. R. Schmidt, Synthesis of methylene bridged C-disaccharides, Tetrahedron Lett. 29 1375 (1988). 

B. Giese and T. Witzel, Synthesis of C-disaccharides by radical C-C bond formation, Angew. Chem. Int. Ed. Engl. 25 450 (1986). 

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