Synthesis of Carbocyclic Nucleosides from 2-Azabicyclo[2.2.1]hept-5-en-3-ones: Sodium Borohydride-Mediated Carbon-Nitrogen Bond Cleavage of Five- and Six-Membered Lactams

Abstract

Various carbocyclic ribofuranosyl nucleosides were stereoselectively synthesized through a small number of steps from 2-azabicyclo[2.2.1]hept-5-en-3-ones by the use of sodium borohydride-mediated C-N bond cleavage as a key step. Ready availability of a novel synthetic precursor, (+)-4/Miydroxymethyl-l/l-ureidocyclopentane-2a,3a-diol [(+)-carbocyclic ribofuranosylurea], provides not only facile routes to carbocyclic ribofuranosylpyrimidines, but also another route to the corresponding cyclopentylamine, (±)-l/l-amino-4/f-hydroxymethylcyclopentane-2a,3a-diol [(±)-carbocyclic ribofuranosylamine], which is useful for the synthesis of the corresponding purine nucleosides. © 1991, The Pharmaceutical Society of Japan. All rights reserved.