The synthesis of polyoxygenated, enantiomerically pure cyclopentane derivatives on route to neplanocin A stereoisomers via alkylidenecarbene species prepared from sugar templates

Our new method for the generation of alkylidenecarbenes, based on the reaction of trimethylsilylazide/Bu2SnO with α-cyanomesylates, has been applied to the synthesis of enantiomerically pure polyhydroxylated cyclopentane derivatives from conveniently functionalized sugar intermediates prepared from d-mannose. The stereoselectivity of the 1,5 C–H insertion reaction leading to the major trans-isomers (8a,b) has been assigned by 1H RMN spectroscopic data, and correctly rationalized by a computational analysis at DFT level. Compounds 8a and 8b have been designed as suitable intermediates for the synthesis of neplanocin A enantiomer.

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