Synthesis and Molecular Structure of New Unsaturated Analogues of Nucleotides Containing Six‐Membered Rings

The reaction of 1‐(chloromethyl)‐3‐(diethoxyphosphonyl)allenes 15 and 16 with purine and pyrimidine bases in the presence of cesium carbonate afforded new acyclic analogs of nucleotides containing a 1,2‐alkadienic skeleton (17−24). Intramolecular cyclization of the alkoxides tethered to the allenyl moiety yielded dihydropyrans 33−38 and dihydrofurans 39 and 40. Dealkylation of the dihydropyrans led to the corresponding phosphonic acids. The molecular structures of new nucleotide analogs 33 and 36 were determined by single‐crystal X‐ray analyses. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)