Synthesis of new nucleoside analogues comprising a methylenecyclobutane unit

Synthesis of eight nucleoside analogues with a methylene cyclobutane unit is described. Wittig or Peterson reactions with protected 2-hydroxycyclobutanones and gave E- and Z-derivatives, respectively. After functional modifications the heterocyclic moieties were introduced via a Mitsunobu reaction either on the lateral chain or on the cycle. When adenine was used in this reaction only the N-9 substitution products were obtained. Removal of the protecting groups provided the target products.