Enantiospecific synthesis of the (4R)-1-azabicyclo[2.2.1]heptane ring system

Abstract

An enantioselective synthesis of (4R)-1-azabicyclo[2.2.1]heptane derivatives is described commencing from readily available trans-4-hydroxy-L-proline which is converted into the key intermediate (3R)-N-(tert-butoxycarbonyl)-3-methylsulfonyloxypyrrolidine 4. Reaction of the sulfonate ester 4 with an enolate anion yields a mixture of (3R)-pyrrolidinylacetic esters 8 and 9 which are reduced to the corresponding alcohols 10 and 11. Conversion of the alcohols into the sulfonate esters 12 and 13 followed by deprotection of the pyrrolidine nitrogen leads to cyclisation yielding the (4R)-1- azabicyclo[2.2.1 ] heptane derivatives 14 and 15.