New Constrained Amines in a Bicyclo[2.2.1]Heptane Skeleton

Abstract

In this paper we present an efficient procedure for obtaining ether-protected bicyclo[2.2.1]heptane amines in six steps, from an optically active keto-alcohol norbornane compound, for building the heterocyclic bases of pyrimidine and purine constrained nucleosides. Trityl as protecting group makes it possible to isolate 5-endo-compounds in pure form by selective crystallization, and to isolate the intermediates in the next 3 steps of the reaction by crystallization. With TBDMS, all compounds were obtained as oil. The direct selective reduction of the keto-alcohol norbornane compound gave the pure 5-endo-diol 4d in high yield, which was then selectively protected at the primary hydroxyl with a trityl group; the next steps are similar for obtaining the trityl-protected bicyclo[2.2.1]heptane amine. The azide intermediates are valuable intermediates for click chemistry.