2-Deoxy-a-glycosides

Scheme 30. Strategies for the chemical synthesis of 2-deoxy-a-glycosides...

Laupichler, L, Sajus, H, Thiem, J, Convenient iodonium-promoted stereoselective synthesis of 2-deoxy-a-glycosides by use of 5 -(2-deoxyglycosyl) phosphorodithioates as donors. Synthesis, 1133-1136, 1992. 

Bielawska, H, Michalska, M, Flighly stereoselective s3mthesis of 2-deoxy-a-glycosides and a-disaccharides, Tetrahedron Lett., 39, 9761-9764, 1998. 

Tatsuta, K, Fujimoto, K, Kinoshita, M, Umezawa, S, Novel synthesis of 2-deoxy-a-glycosides, Carbohydr. Res., 54, 85-104, 1977. 

Toshima, K, Nagai, H, Ushiki, Y, Matsumura, S, Novel glycosidations of glycals using BCI3 or BBrs as a promoter for catalytic and stereoselective syntheses of 2-deoxy-a-glycosides, Synlett, 1007-1009, 1998. 

Tatsuta s oleandomycin synthesis is based on the construction of the aglycone by coupling of the C1-C7 (131) and Cg-Ci3 (136) segments, which are derived from L-rhamnose and (S)-( + )-methyl 3-hydroxy-2-methylpropionate, respectively, and on the stereo- and regioselective introduction of the two sugar moieties. Methods for selective esterification and for the synthesis of 2-deoxy-a-glycosides were developed in the course of the synthesis. 

Stereo- and regioselective introduction of the two sugar moieties. The stereoselective formation of the 2-deoxy-a-glycoside (Tatsuta s method) was developed and illustrated (29). 

Simple alkoxides react upon these a-adducts to give 2-deoxy-P-glycosides according to a Sn mechanism [97]. Activation by thiophilic promoters such as silver perchlorate in acetonitrile [96], or NIS in dichloromethane, or IDCP in acetonitrile [98] leads with alcohols mainly to 2-deoxy-a-glycosides. 2 -Deoxy-a-disaccharides (147) can thus be prepared in good yields, but with a p ratios better than 9 I only in a few eases (sugar alcohol 146). 

The unstable phosphate 150 reacts with alcohols in the presence of magnesium perchlorate to give mainly 2-deoxy-a-glycosides 132 in good yields (a 3 ratio 2.3-4.5 1). 

Tatsuta [107] reported that highly a-stereoselective glycosylation of phenyl 2-deoxy-3,4-0-isopropylidene-l-thio-D-fucopyranoside 158 could be accomplished because of its rigid and unusual boat conformation. 2-Deoxy-a-glycosides (161 versus 159) were obtained with a much lower selectivity from 2-deoxyfucosyl donors 160 in an usual (d) chair conformation (Scheme 37). It was also shown that... 

SCHEME 38.31. Solid phase synthesis of 2-deoxy-a-glycoside using 2-deoxy-2-selenophenylgly-cosyl fluoride. 

Sherry BD, Loy RN, Toste FD.Rhenium(V)-catalyzed synthesis of 2-deoxy-a-glycosides. J. Am. Chem. Soc. 2004 126 451(L4511. 

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