Choline sodium 4-amino-1-β-d-ribofuranosyl-2-(1H)-pyrimidionone diphosphate tetrahydrate (Sodium cytidine diphosphocholine,C14H33N4NaO15P2)

This communication presents a preliminary report on the crystal structure of this important nucleotide, involved in lecithin synthesis in animal tissues. The crystallographic data were recorded using a four-circle diffractometer with Cu-K x-radiation. Crystal data: orthorhombic, space groupP2₁2₁2₁ (No. 19),Z = 4,a = 6.98 pm,b = 123.6 pm,c = 292.3 pm,U = 2.522 nm³. The structure was solved by means of a Patterson and electron-density maps and refined by several cycles of least-squares using isotropic temperature factors toR = 0.14.The torsion angles associated with the furanosyl ring are, in general, at the very extreme of the range commonly observed for C(2) endopuckering (Altona and Sundaralingam, 1972); their values are 1 = 319 °, 2 = 47 °, 3 = 326 °, 4 = 13 °, 5 = 18 °. The phase angle of pseudorotation, calculated from these values using the formula given by Altona and Sundaralingam (1972) is 139 °. This shows the ribose ring to be slightly nearer to the C(1) exopuckering than the C(2) endopuckering conformation, but remote from being a C(3) endo-conformer. The sugar ring, in fact, is very close to being an idealized twist conformer. This is supported by a four-atom least-squares planes study, and is consistent with the high value of 237 ° (Sundaralingam, 1973).Backbone torsion angles associated with the structure are = 57 °, = 133 °, = 174 °, and = 291 °. is some 7 ° less than the preferred minimum value for C(2) endopuckering.