Efficient synthesis of novel carbocyclic nucleosides via sequential Claisen rearrangement and ring-closing metathesis

Very efficient synthetic route to novel 4′α-C-hydroxymethyl branched carbocyclic nucleosides was described. The stereocontrolled synthesis of target nucleosides was successfully achieved by Johnson orthoester–Claisen rearrangement, ring-closing metathesis (RCM) starting from a simple acyclic precursor 1,3-dihydoxy acetone 1. Nucleosidic bases (adenine and cytosine) were coupled by Pd(0)-catalyzed allylic alkylation in a highly regiocontrolled manner.