Water molecules in the crystal structure of tricyclic acyclovir.

The biologically important molecule tricyclic acyclovir, presented here as 3-[(2-hydroxyethoxy)methyl]-6-methyl-3H-imidazolo[1,2-a]purin-9(5H)-one dihydrate, C11H13N5O3*2H2O, shows conformational flexibility, which is observed in the solid state as two symmetrically independent molecules with different side-chain conformations. Additionally, one of these molecules exhibits side-chain disorder, such that there are three different conformations in the crystal. Water molecules found in the crystal form (H2O)8 clusters which are located between molecules of tricyclic acyclovir. The complex hydrogen-bond network formed between water and tricyclic acyclovir in the solid state may be related to the solvation of the molecules in solution.

Diverse reactivity of dialkylaluminum dimesitylboryloxides [(mu-Mes2BO)AlR2]2. Synthetic and structural study.

Several stable dimeric dialkylaluminum boryloxides of the formula [(mu-Mes2BO)AlR2]2 (R = Me (1), Et (2), iBu) have been prepared from dimesitylborinic acid Mes2BOH and trialkylaluminums R3Al. Compound 1 has been characterized by X-ray diffraction. These compounds exhibit diverse reactivity toward protonolytic reagents depending on the bulkiness of these reagents. Treatment of 1 with tert-butyl alcohol afforded crystalline species trans-[mu-tBuO)(Mes2BO)AlMe]2 (3), which is the first example of a mixed system containing boryloxide and alkoxide ligands together. Most surprisingly, Mes2BOH was found to undergo catalytic decomposition in the presence of [(mu-Mes2BO)AlR2]2 via the unexpected cleavage of one boron-carbon bond. The molecular structure of the decomposition product, i.e., trimesitylboroxin [MesBO]3 (4) is reported.

Conformational comparison of 1,2-dimethyl-6-oxo-1,6-dihydro-3,4'-bipyridine-5-carbonitrile free base and its hydrobromide monohydrate salt.

C13H11N3O (I), Mr = 225.25, monoclinic, P21/c, a = 11.713 (4), b = 7.891 (3), c = 12.154 (4) A, beta = 92.27 (4) degrees, V = 1123 (1) A3, Z = 4, Dx = 1.333 Mg m-3, lambda (Mo K alpha) = 0.71073 A, mu = 0.082 mm-1, F(000) = 472, T = 293 K, R = 0.063 for 2579 reflections. 5-cyano-1,2-dimethyl-6-oxo-1,6-dihydro-3,4'-bipyridinium bromide monohydrate, C13H12N3O+.Br-.H2O (II), Mr = 324.18, orthorhombic, Pbca, a = 7.2893 (8), b = 18.955 (3), c = 19.814 (3) A, V = 2738 (1) A3, Z = 8, Dx = 1.573 Mg m-3, lambda (Mo K alpha) = 0.71073 A, mu = 2.972 mm-1, F(000) = 1312, T = 293 K, R = 0.086 for 2292 reflections. The twist angle around the bipyridine C(1)-C(1)' bond is 66.6 (2) and 44.1 (8) degrees for the free base (I) and its salt (II), respectively. The larger C(3)'-N(4)'-C(5)' pyridine ring angle [121.8 (5) degrees] in the salt structure compared with the corresponding value for the free base [116.1 (1) degrees] suggests that N(4)' is a protonation site. The water molecule in the salt structure (II) is disordered with occupancy refined to 0.6 and 0.4.