Synthesis and Structure of Dinucleotides with S‐Type Sugar Puckering and Noncanonical ϵ and ζ Torsion Angle Combination (ν 2 ,ϵ,ζ‐D‐CNA)

The synthesis of the diastereoisomers of ν 2 ,ϵ,ζ‐D‐CNA dinucleotide building units of nucleic acids and their (2′,5′)‐ν 2 ,ϵ′,ζ′‐D‐CNA analogues, in which the ϵ and ζ torsional angles are stereocontrolled by a dioxaphosphorinane ring structure (D‐CNA family) is described from a common 3‐deoxy‐3‐(hydroxymethyl)‐ D ‐allofuranose intermediate. NMR spectroscopic and circular dichroism structure analysis of ν 2 ,ϵ,ζ‐D‐CNA shows that the sugar puckering is fixed in the C‐2′‐ endo conformation and that these D‐CNA structuralelements allow stabilization of the ϵ/ζ torsion angle combinations, which are significantly different from the typical combinations observed in canonical A‐ or B‐form duplexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)