Dinucleotides of 4′-C-vinyl- and 5′-C-allylthymidine as substrates for ring-closing metathesis reactions

Thymidine derivatives containing a 4'-C-vinyl group or a 5'-C-allyl group are synthesized and used as building blocks for three different dinucleotides. These are evaluated as substrates for ring-closing metathesis cyclisations, and a protected 5'-C-allylthymidine homo-dimer is found to be the most reactive. A protected precursor for a conformationally restricted cyclic dinucleotide with a four carbon 5'-C to 5'-C connection is hereby efficiently obtained, whereas a corresponding three carbon 4'-C to 5'-C connection is obtained in a lower yield. (C) 2003 Elsevier Ltd. All rights reserved.