Fructose branched-chain derivatives

A useful application of the chemistry shown in Scheme 83 is the synthesis of branched-chain functionalized carbohydrates. For this purpose two epoxides 261 and 262 derived from D-glucose and 263 derived from D-fructose were prepared following reported methodologies, and were submitted to a DTBB-catalyzed lithiation as described above in Scheme 83. The expected intermediates 264-266 and final products 267-269 were prepared in a regio- and stereoselective manner in 15- 95% yield" Also here, the use of a prochiral electrophile gave equimolecular amounts of both diastereomers. 

The value of the 1,3-dithian route to branched-chain sugar derivatives has been illustrated further by stereospecific syntheses of 3-C-formyl, 3-C-hydroxymethyl, and 3-C-methyl derivatives of D-psicose from the ketone (373) via the dithianyl adduct (374). Addition of nitromethane to (373) gave both 3-C-nitromethyl-o-psicose and -fructose derivatives, which, after separation by chromatography, were reduced to the corresponding 3-C-aminomethyl derivatives. The use of dithianyl derivatives in the synthesis of streptomycin components is dealt with in Chapter 18. 

D-Fructose 1,6-diphosphate aldolase has been used to catalyse aldol condensations on some branched-chain sugar derivatives. For example the deoxytetrose (15) afforded the... 

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