Nucleosides and Nucleotides. 191. Ring Expansion Reaction of 1-[2,3,5-Tri-O-TBS-4#alpha#-formyl-#beta#-D-ribo-pentofuranosyl]uracil by Treating with (Methylene)triphenylphosphorane to Give a New Nucleoside Containing Dihydrooxepine Ring at the Sugar

摘要

When 1-[2,3,5-tri-O-TBS-4#alpha#-formyl-#beta#-D-ribo-pentofuranosyl]uracil (5) was treated with (methylene)triphenylphosphorane in THF, an unusual ring-expansion reaction occurred to give a nucleoside (7) containing dihydrooxepine ring at the sugar moiety. A deuterium-label experiment showed that one carbon unit derived from the ylide was incorporated into the 5'-position of 7. A ring cleavage between the C-3' and C-4' of 5 during the reaction was suggested.