Bis C-aryl glycosides

Bis-C-aryl glycosides as model kidamycins are mentioned in Chapter 3, and amino acid analogues of 3-deoxyprumycin are referred to in Chapter 9. Cyclophellitol and its diastereomers are covered in Chapter 18, and the synthesis of intermediates for antibiotics is mentioned in Chapter 24. 

Matsumoto, T, Katsuki, M, Suzuki, K, Bis(cyclopentadienyl)dichlorozirconium-silver perchlorate (Cp2ZrCl2-AgC104) efficient promoter for the Friedel-Crafts approach to C-aryl glycosides. Tetrahedron Lett., 30, 833-836, 1989. 

Bis-C-aryl- and bis-C-alkynylaryl-glycosides such as 98 were introduced by Vasella and collaborators [168,280]. Aromatic ethynyl spacers have been built up by Sonogashira coupling [281,282]. 

Use as an Electrophile. The chlorosilane function is highly electrophilic and can react with a variety of nucleophiles, for instance with an aryllithium carbanion, to provide silyl derivatives. The (bromomethyl)chlorodimethylsilane can also be utilized as a bis-electrophilic reagent, thanks to the bromomethylene function. Initial substitution of chlorine by an aryllithium or an aryl Grignard followed by the displacement of bromine by a phenoxide anion provided valuable linkages for solid phase s)m-thesis. Based on the same idea, Martin proposed a new synthesis of unsymmetrical C-aryl glycosides. Orthometallation of a furyl moiety followed by silylation sets a diene on a silicon tether. The masked dienophile (a benzyne) is then introduced by 0-alkylation. The cycloadduct was then converted to various naphthol derivatives (eq 25). 

Bicyclic aromatic [283,284] or triazole [285] spacers were used to arrange oligosaccharides in a parallel fashion to investigate mimicry of cellulose I and II. Interesting aryl C,5-bis-glycosides of type 89 (O Scheme 17) have been obtained during the work on antithrombotic 1,5-dithiopyranosides [286]. 

Halogenoacetals generating the type F radicals were used by De Mesmaeker in the synthesis of C-glycosides and C-2 branched pyranosides [70]. Easy access to furobenzofurans was provided as shown in the conversion of the aryl bromide 102 into the product 103 in a formal synthesis of aflatoxin Bi (104) by Snieckus [71] (Scheme 36). 

Hosoya T, Ohashi Y, Matsumoto T, Suzuki K (1996) On the stereochemistry of aryl C-glycosides unusual behavior of bis-TBDMS protected aryl C-olivosides. Tetrahedron Lett 37 663-666... 

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