Bis(mu-N-[2-(eta[5]-cyclopentadienyl)-ethyl]-4-toluenesulfonamido-N,O:O')-bis[bis(trifluoromethanesulfonato-O)-titanium(II)]bis(dichloromethane) solvate.

The title compound, [Ti(2)(CF(3)O(3)S)(4)(C(14)H(15)NO(2)S)(2)].2CH(2)Cl(2), consists of unique centrosymmetric dimers, with an eight-membered ring derived from the monomer subunits by formation of two Ti-(N,O)-S-O head-to-tail sequences around a crystallographic inversion centre, and two ordered dichloromethane solvate molecules. The Ti ion has distorted octahedral coordination, through the N atom and one O atom of one p-toluenesulfonamido group linked by an ethyl group to the bound cyclopentadiene moiety, one O atom from the other p-toluenesulfonamido group and two singly bound trifluoromethanesulfonates moieties which are coordinated in pseudo-cis positions. Both Ti-O(sulfonamido) bond lengths [2.149 (3) and 2.388 (3) A] are considered bonding interactions.

(N-[2-(eta[5]cyclopentadienyl)ethyl]-4-toluenesulfonamido-N,O)(tetrahydrofuran-O)bis(trifluoromethanesulfonato-O)titanium(II).

The title compound, [Ti(CF(3)O(3)S)(2)(C(14)H(15)NO(2)S)(C(4)H(8)O)], contains a unique ligand system in which the Ti ion is bound to the N and O atoms of a 2-p-toluenesulfonamide ligand, which is linked by an ethyl group to a coordinated cyclopentadiene moiety. The distorted octahedral geometry about the Ti ion is completed by two trifluoromethanesulfonate ligands and a tetrahydrofuran molecule. Comparison with related compounds shows that both the Ti-N and Ti-O bonds of the sulfonamide, although longer than normal values, indicate significant bonding interactions.

Transition state structure of purine nucleoside phosphorylase and principles of atomic motion in enzymatic catalysis.

Immucillin-H [ImmH; (1S)-1-(9-deazahypoxanthin-9-yl)-1,4-dideoxy-1,4-imino-D-ribitol] is a 23 pM inhibitor of bovine purine nucleoside phosphorylase (PNP) specifically designed as a transition state mimic [Miles, R. W., Tyler, P. C., Furneaux, R. H., Bagdassarian, C. K., and Schramm, V. L. (1998) Biochemistry 37, 8615-8621]. Cocrystals of PNP and the inhibitor are used to provide structural information for each step through the reaction coordinate of PNP. The X-ray crystal structure of free ImmH was solved at 0.9 A resolution, and a complex of PNP.ImmH.PO(4) was solved at 1.5 A resolution. These structures are compared to previously reported complexes of PNP with substrate and product analogues in the catalytic sites and with the experimentally determined transition state structure. Upon binding, ImmH is distorted to a conformation favoring ribosyl oxocarbenium ion formation. Ribosyl destabilization and transition state stabilization of the ribosyl oxocarbenium ion occur from neighboring group interactions with the phosphate anion and the 5'-hydroxyl of the ribosyl group. Leaving group activation of hypoxanthine involves hydrogen bonds to O6, N1, and N7 of the purine ring. Ordered water molecules provide a proton transfer bridge to O6 and N7 and permit reversible formation of these hydrogen bonds. Contacts between PNP and catalytic site ligands are shorter in the transition state analogue complex of PNP.ImmH.PO(4) than in the Michaelis complexes of PNP.inosine.SO(4) or PNP.hypoxanthine.ribose 1-PO(4). Reaction coordinate motion is dominated by translation of the carbon 1' of ribose between relatively fixed phosphate and purine groups. Purine and pyrimidine phosphoribosyltransferases and nucleoside N-ribosyl hydrolases appear to operate by a similar mechanism.

1D-3,4-Di-O-(diphenylmethylphosphonio)-1,2,5, 6-tetra-O-methyl-chiro-inositol diiodide.

The title compound, 3,4,5,6-tetramethoxycyclohexane-1, 2-diyldioxybis(methyldiphenylphosphonium) diiodide, C(36)H(44)O(6)P(2)(2+).2I(-), was prepared from a New Zealand natural product, D-chiro-inositol, in order to develop new catalytic metal complexes. The inositol ring retains its usual chair conformation with only minor perturbations caused by the bound diphenylmethylphosphines. Crystal-packing forces are provided by C-H. I cation-anion interactions.

The synthesis and antibacterial activity of totarol derivatives. Part 3: Modification of ring-B.

Ring-B derivatization of totarol (1) afforded the series of compounds 2-22 which were screened in vitro against: beta-lactamase-positive and high level gentamycin-resistant Enterococcus faecalis, penicillin-resistant Streptococcus pneumoniae, methicillin-resistant Staphylococcus aureus (MRSA), and multiresistant Klebsiella pneumoniae. Several of the derivatives retained much of the antibacterial activity of totatol against the first three of these organisms (all gram-positive), but none was more active. The gram-negative Klebsiella was resistant to all compounds examined. Totarol (1) was shown to uncouple oxidative phosphorylation in isolated mitochondria at 50 microM.

Isolation and structural characterization of triethanolaminotitanatranes: X-ray structures of partial hydrolysis condensates.

A family of triethanolamine complexes of titanium with varying metal/ligand ratios have been prepared from reactions of titanium tetraisopropoxide with triethanolamine. Three nonhydrolytic products, having essentially all isopropoxide ligands substituted by triethanolamine, were prepared as hygroscopic, glassy solids. Crystals of two hexameric titanatrane partial hydrolysis analogues [Ti3(mu 2-O)((HOCH2CH2)2NCH2CH2O)(OCH2CH2)2(mu 2-OCH2CH2)N)2(OCH2CH2)(mu 2- OCH2CH2)2N)]2 (1), and [Ti3(mu 2-O)(OCH(CH3)2)((OCH2CH2)2(mu 2-OCH2CH2)N)2(OCH2CH2)(mu 2- OCH2CH2)2N)]2 (2) were isolated and structurally characterized. The structures consist of a central core of two oxo-bridged dititanatranes (TEA)TiOTi(TEA) (TEAH3 = triethanolamine) with the nonhydrolytic residue (TEA)Ti(TEAH2) included as an adduct in (1), analogously to (TEA)Ti(OPri) in (2).