[reaction: see text] A fast and efficient synthetic route to novel Northern locked carbocyclic nucleosides (as precursors of carbocyclic locked nucleic acids or cLNAs) is described. The target nucleoside with a oxabicyclo[2.2.1]heptane ring system was prepared from a simple starting material, diethyl malonate. Ring closure by intramolecular O-alkylation provided the target ring system as the major isomer over the [3.2.0] oxetane system. The adenine moiety was introduced through a reactive triflate after inversion of the stereochemistry of the corresponding alcohol by oxidation and reduction.
Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
