Concise Synthesis of Optically Active Cyclopropane β-Amino Acid Derivatives via Olefination of Cyclopropanone Surrogates.

An expedient synthesis of cyclopropane β-amino acid derivatives is reported from readily accessible cyclopropanone surrogates. The addition of stabilized phosphorus ylides to 1-sulfonylcyclopropanols leads to the formation of highly electrophilic alkylidenecyclopropanes shown to be reactive in a telescopic aza-Michael reaction, in mild conditions. The transformation proceeds with complete diastereocontrol in favor of the products and is amenable to the rapid production of highly enantioenriched β-amino acid derivatives, peptidomimetics and spirocyclic analogues.