Resin glycosides synthesis

Scheme 45 Macrocyclization by RCM in Fiirstner s total synthesis of the resin glycoside woodrosin I (218) [104]...

The synthesis of the disaccharide subunit 85 of tricolorin A, a cytotoxic resin glycoside isolated from lpomoea tricolor, provides a unique opportunity to compare the efficiency of an RCM-based macro cyclization reaction with that of a more conventional macrolactonization strategy. Furthermore, this specific target molecule challenges the compatibility of the catalysts with various functional groups. 

Fiirstner A, Muller T (1998) Metathesis Route to Resin Glycosides Formal Total Synthesis of Tricolorin A. J Org Chem 63 424... 

Unique glycolipids produced by plants are the resin glycosides for which the first synthesis was based on the trichloroacetimidate method [293,294]. Other members of this family have been... 

The acid used in the Fischer glycoside synthesis was originally HCl (which made the kinetic data reproducible only with difficulty, as in methanol HCl is slowly consumed to form methyl chloride). Nowadays, ion-exchange resins are used preparatively, whilst the data on 4- and 5-O-methylated glycosides were obtained with camphor sulfonic acid. 

Furstner, A., Muller, T., Efficient total synthesis of resin glycosides and analogues by ring-closing olefin metathesis, J. Am. Chem. Soc. 1999, 121 7814-7821. 

The performance and excellent application profile of RCM are illustrated by the total synthesis of various resin glycosides and sugar-based macrodiolides such as tricolorins A and G, woodrosin I, and ipomoeassins B and E (Scheme 5.47). The synthesis of these amphiphilic natural products has resulted in the advancement of carbohydrate chemistry and is due to Ftirsner et al. who have recently reviewed their effort in this area [86]. In this review, they fully detail the syntheses of tricolorins A (208) (Equation 1, Scheme 5.47) and G (211) (Equation 2, Scheme 5.47), two natural products isolated from Ipomea tricolor, which are plant growth inhibitors... 

This synthesis demonstrated that the neighboring-group participation effect on the stereoselectivity of glycosylation reactions can be extended to sohd-phase processes. In this case, milder and more practical cleavage conditions than previously discussed were established. The use of /V- bromosuccinimide as the thiophilic reagent in acetone/water or tetrahydrofuran/methanol permitted the release of oligosaccharides in form of lactols or 1-0-Me glycosides, respectively. The tetrasaccharide derivative was isolated in 34% yield from thiol resin 3 (80% yield per step). 

This book covers all of the most recent (at the time of writing) developments in the field of solid support oligosaccharide synthesis. Included are chapters discussing different synthetic strategies, glycosylation protocols, the use of solid supports versus soluble polymeric supports and on-resin analytical methods. Special topics such as the formation of [3-glycosidic linkages on solid support are also discussed. 

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