Elementary patterns in protein–nucleic acid interactions. VI. Structures of 3-(7-adeninyl)propionamide monohydrate, C8H10N6O.H2O

Abstract

M r = 224.2, monoclinic, P2~/c, a = 9.850(1), b = 2 8 . 3 2 6 (1), c = 7 . 2 6 1 ( 1 ) , ~ , t = 96.63 (1) °, V = 2012.4/~3, D m = 1.48, D x = 1.480 Mg m -a, Z = 8, 2(Cu Ka) -1.54184 ,/k; R = 0.057 for 3079 diffractometer-measured intensities. The two independent molecules in the asymmetric unit form a dimer, with hydrogen bonds between the carbamoyl group of one molecule and the adenine N(1)of another. This N H . . . N hydrogen bond may suggest a strong affinity of the carbamoyl group for adenine N(1). Introduction. As part of a study on elementary patterns of interaction between amino acid residues and purinepyrimidine bases, the title compound was prepared by esterification followed by ammonolysis of 3-(7adeninyl)propionic acid which is obtained together with 3-(9-adeninyl)propionic acid and 3-(7-adeninyl)propionic acid lactam in the reaction reported by Kondo, Sato & Takemoto (1973). Experimental. Prismatic crystals (from a methanolwater solution), 0.5 x 0.25 x 0.05 mm, D m by flotation in a mixture of cyclohexane and carbon tetrachloride, Weissenberg photographs showed systematic absences (hOl l odd, 0k0 k odd) of P21/c; Rigaku automated four-circle diffractometer, Ni-filtered Cu Ka radiation (2= 1.54184/1,); unit-ceU dimensions determined by least squares with the 20 values of 48 high-angle reflexions; intensity data in the range 5 ° Fnm ) included in least-squares calculation by assuming F o = Fnm and w = o'(Flim); final R = 0 . 0 5 7 for 3079 measured reflexions ( w R = 0.054), maximum shift of parameters in the last cycle 0. la; atomic scattering factors from International Tables for X-ray Crystallography (1974); F(000) = 944. Discussion. Atomic parameters are listed in Table 1.* Bond distances and angles in molecules A and B are shown in Fig. 1. The values in the two adenine moieties are similar to each other and, in general, to those found in 7-substituted purine derivatives (Takenaka, Nakano & Sasada, 1979; Watson, Sweet & Marsh, 1965). The purine moieties are planar with maximum shifts of 0.029/~ at C(5A) and 0.016 ,/k at N(1B). N(6A) and N(6B) deviate by 0.058 and 0.037 A, respectively, from their purine planes. The conformation of the ethyl chain with the carbamoyl group is similar to that found in the complex 3(9adeninyl)propion amide1methylthymine dihydrate (Takimoto, Takenaka & Sasada, 1982), but different from that of 3-(9adeninyl)propionamide (Takimoto, Takenaka & Sasada, 1981). In the present crystal, the torsion angles N(7) -C(11) -C(12) -C(13) and C(11) -C(12) C(13)--N(13) are 39.6(3) and -134 .6 (3 ) ° , respectively, in A; the corresponding values in B are 4 7 . 2 (3) and 122.5 (3) ° . The dimensions of the carbamoyl group are similar to those of 3-(9-adeninyl)propionamide. The hydrogen-bond distances and angles are given in Table 2. Molecules A and B in the asymmetric unit form a pair through hydrogen bonds between carbamoyl N(13)H and adenine N(1) and are related by the pseudo inversion centre. The dihedral angle between the purine plane of A and the carbamoyl plane of B is 63.2(1) ° [the torsion angle C(13A)-N(13A).. . * Lists of structure factors, anisotropic thermal parameters of C, N and O atoms, atomic parameters of H atoms, bond angles involving H atoms, the least-squares planes of the purine ring and the carbamoyl group and hydrogen-bond distances and angles involving H atoms have been deposited with the British Library Lending Division as Supplementary Publication No. SUP 38082 (19 pp.). Copies may be obtained through The Executive Secretary, International Union of Crystallography, 5 Abbey Square, Chester CH1 2HU, England. 0108-2701/83/010073-03501.50 © 1983 InternationalUnion of Crystallography 74 3-(7-ADENINYL)PROPIONAMIDE MONOHYDRATE Table 1. FractDnal coordinates and equivalent isotrop& temperature fac tors B values are the equivalent isotropic temperature factors calculated from the anisotropic thermal parameters using the equation B = 8z~2(U~ + U 2 + U~)/3, where U v U v and U3 are principal components of the mean-square displacement matrix O. Values in angle brackets are the anisotropicity defined by [Y(B--8zr2Ui)2/3] u2. The e.s.d.'s in parentheses refer to the last