A C3′ modified nucleotide. The difluorophosphonate function, a phosphate mimic, governs the conformational behaviour of the ribofuranose

A conformational analysis using the Pseurot 6.3 software package of a modified nucleoside-3′-phosphate is reported and reveals that the phosphate mimic strongly influences the conformational behaviour of the ribose ring and shifts the North/ South equilibrium to a northern position. A rational classification by the group electronegativity of several phosphate analogues is presented. The λ factor of the difluorophosphonate group in water (Diez–Donders generalised Karplus equation) is also determined.