Synthesis and Structures of (Dialkylamino)ethylcyclopentadienyl Derivatives of Zinc

Binding affinity of substituted ureido-benzenesulfonamide ligands to the carbonic anhydrase receptor: a theoretical study of enzyme inhibition

The binding properties of a series of benzenesulfonamide inhibitors (4-substituted-ureido-benzenesulfonamides, UBSAs) of human carbonic anhydrase II (hCA II) enzyme with active site residues have been studied using a hybrid quantum mechanical/molecular mechanical (QM/MM) model. To account for the important docking interactions between the UBSAs ligand and hCA II enzyme, a molecular docking program AutoDock Vina is used. The molecular docking results obtained by AutoDock Vina revealed that the docked conformer has root mean square deviation value less than 1.50 Å compared to X-ray crystal structures. The inhibitory activity of UBSA ligands against hCA II is found to be in good agreement with the experimental results. The thermodynamic parameters for inhibitor binding show that hydrogen bonding, hydrophilic, and hydrophobic interactions play a major role in explaining the diverse inhibitory range of these derivatives. Additionally, natural bond orbital analysis is performed to characterize the ligand-metal charge transfer stability. The insights gained from this study have great potential to design new hCA-II inhibitor, 4-[3-(1-p-Tolyl-4-trifluoromethyl-1H-pyrazol-3-yl)-ureido]-benzenesulfonamide, which belongs to the family of UBSA inhibitors and shows similar type of inhibitor potency with hCA II. This work also reveals that a QM/MM model and molecular docking method are computationally feasible and accurate for studying substrate-protein inhibition.

Late metal salicylaldimine complexes derived from 5-aminosalicylic acid — Molecular structure of a zwitterionic mono Schiff base zinc complex

Condensation of salicylaldehyde (2-HOC6H4C(O)H) with 5-aminosalicylic acid (5-H2NC6H3-2-(OH)-CO2H) afforded the Schiff base 2-HOC6H4C(H)=NC6H3-2-(OH)-5-CO2H (a). Similar reactivity with 5-bromosalicylaldehyde was also observed to give 5-Br-2-HOC6H3C(H)=NC6H3-2-(OH)-5-CO2H (b). Reaction of these salicylaldehydes with Pd(II), Cu(II), and Zn(II) salts gave the corresponding bis(N-arylsalicylaldiminato)metal complexes (M = Pd (1), Cu (2), Zn (3)). The molecular structure of the Schiff base compound a has been confirmed by an X-ray diffraction study. Crystals of a were monoclinic, space group P2(1)/c, a = 7.0164(7) Å, b = 11.0088(11) Å, c = 14.8980(15) Å, β = 102.917(2)°, Z = 4. The molecular structure of a novel zwitterionic conformer of 3a was also characterized by an X-ray diffraction study. Crystals of 4 were monoclinic, space group P2(1)/c, a = 9.5284(5) Å, b = 19.5335(11) Å, c = 8.6508(5) Å, β = 90.596(1)°, Z = 4. All new compounds have been tested for their antifungal activity against Aspergillus niger and Aspergillus flavus. Key words: 5-aminosalicylic acid (5-ASA), antifungal, copper, palladium, salicylaldimines, Schiff base, zinc.

Discrete Metal-Based Catalysts for the Copolymerization of CO2 and Epoxides: Discovery, Reactivity, Optimization, and Mechanism

Most synthetic polymers are made from petroleum feedstocks. Given the non-renewable nature of these materials, there is increasing interest in developing routes to polymeric materials from renewable resources. In addition, there is a growing demand for biodegradable polymeric materials. Polycarbonates made from CO(2) and epoxides have the potential to meet these goals. Since the discovery of catalysts for the copolymerization of CO(2) and epoxides in the late 1960's by Inoue, a significant amount of research has been directed toward the development of catalysts of improved activity and selectivity. Reviewed here are well-defined catalysts for epoxide-CO(2) copolymerization and related reactions.

Concerning the Mechanism of the Ring Opening of Propylene Oxide in the Copolymerization of Propylene Oxide and Carbon Dioxide To Give Poly(propylene carbonate)

The reactions between (TPP)AlX, where TPP = tetraphenylporphyrin and X = Cl, O(CH(2))(9)CH(3), and O(2)C(CH(2))(6)CH(3), and propylene oxide, PO, have been studied in CDCl(3) and have been shown to give (TPP)AlOCHMeCH(2)X and (TPP)AlOCH(2)CHMeX compounds. The relative rates of ring opening of PO follow the order Cl > OR > O(2)CR, but in the presence of added 4-(dimethylamino)pyridine, DMAP (1 equiv), the order is changed to O(2)CR > OR. From studies of kinetics, the ring opening of PO is shown to be first order in [Al]. Carbon dioxide inserts reversibly into the Al-OR bond to give the compound (TPP)AlO(2)COR, and this reaction is promoted by the addition of DMAP. The coordination of DMAP to (TPP)AlX is favored in the order O(2)C(CH(2))(6)CH(3) > O(2)CO(CH(2))(9)CH(3) >> O(CH(2))(9)CH(3). The microstructure of the poly(propylene carbonate), PPC, formed in the reactions between (TPP)AlCl/DMAP and (R,R-salen)CrCl and rac-PO/S-PO/R-PO and CO(2), has been investigated by (13)C [(1)H] NMR spectroscopy. The ring opening of PO is shown to proceed via competitive attack on the methine and methylene carbon atoms, and furthermore attack at the methine carbon occurs with both retention and inversion of stereochemistry. On the basis of these results, the reaction pathway leading to ring opening of PO can be traced to an interchange associative mechanism, wherein coordination of PO to the electrophilic aluminum atom occurs within the vicinity of the Al-X bond (X = Cl, OR, O(2)CR, or O(2)COR). The role of DMAP is two-fold: (i) to labilize the trans Al-X bond toward heterolytic behavior, and (ii) to promote the insertion of CO(2) into the Al-OR bond.