Furyl glycosides

Scheme 1 Synthesis of trihydroxyalkyl-substituted furans derivatives 3 or 4 from D-pentose and C-furyl glycosides 5 or 6 from D-hexoses...

A number of modified sugars have been obtained by using the aforementioned approach. For example, methyl 4-0-methyl-5,5-di-C-methyl-p-DL-lyxoside, the glycoside of the sugar component of the antibiotic novobiocin, was synthesized with high selectivity from 2-(2-furyl)propan-2-ol. Methyl 6-acetamido-6-deoxy and 6-deoxy-6-nitro-a-DL-mannopyranosides were prepared from suitably substituted 2-furylethanols. 1,4-Addition of an active methylene compounds to... 

In our laboratory we have developed a novel approach to the synthesis of an enantiopure AB segment of the anthracyclinones based on a new type of chiral substrate, enone 131 [131,132]. Di-O-acetyl-L-rhamnal (129), obtained from L-rhamnose, was converted into benzyl glycoside 130 [133] by the Perrier procediue [134], Hydrolysis and oxidation of the C-4 (carbohydrate numbering) hydroxyl group in 130 gave enone 131 in 67% overall yield (Scheme 27). It is worthy of note that uloside 131 is also readily available from a non-sugar chiral pool. Enzymatic resolution of racemic l-(2-furyl)ethanol yielded the (S)-enantiomer 138 in 98% ee [135]. This was transformed in two steps, by known procedures, into ulose 139 (Scheme 28) [136,137] from which uloside 131 was readily obtained. 

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). 

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