title: Computer-aided design (CAD) of Mn(II) complexes: superoxide dismutase mimetics with catalytic activity exceeding the native enzyme.
abstract: New Mn(II) macrocyclic pentaamine complexes derived from the biscyclohexyl-pyridine complex, M40403 ([manganese(II)dichloro[(4R,9R,14R,19R)-3,10,13,20,26-pentaazatetracyclo[20.3.1.0.(4,9)0(14,19)]hexacosa-1(26),-22(23),24-triene]]), are described here. The complex M40403 was previously shown to be a superoxide dismutase (SOD) catalyst with rates for the catalytic dismutation of superoxide to oxygen and hydrogen peroxide at pH = 7.4 of 1.2 x 10(+7) M(-1) s(-1).(1) The use of the computer-aided design paradigm reported previously for this class of Mn(II) complexes(2,3) led to the prediction that the 2S,21S-dimethyl derivative of M40403 should possess superior catalytic SOD activity. The synthesis of this new macrocyclic Mn(II) complex, [manganese(II)dichloro[2S, 21S-dimethyl-(4R,9R,14R,19R)-3,10,13,20,26-pentaazatetracyclo[20.3.1.0.(4,9)0(14,19)]hexacosa-1(26),22(23),24-triene]], 5, was accomplished via a high yield template condensation utilizing the linear tetraamine, N,N'-Bis[(1R,2R)-[2-(amino)]cyclohexyl]-1,2-diaminoethane, 1, 2,6-diacetylpyridine, and MnCl(2) to form the macrocyclic diimine complex, 2, which then is reduced. The two other possible dimethyl diastereomers of 5 (2R,21R-dimethyl,3, and 2R,21S-dimethyl, 6) were also prepared via reduction of the diimine complex 2. Two of these complexes, 3 and 5, were characterized by X-ray structure determination confirming their absolute stereochemistry as 2R,21R-dimethyl and 2S,21S-dimethyl, respectively. The results of the MM calculations which predict that the 2S,21S-dimethyl complex, 5, should be a high activity catalyst and that the 2R,21R-dimethyl complex, 3, should have little or no catalytic activity are presented. The catalytic SOD rates for these complexes are reported for each of these complexes and a correlation with the modeling predictions is established showing that 2R,21R-complex, 3, has no measurable catalytic rate, while the 2R,21S complex, 6, is identical to M40403, and the 2S,21S- complex, 5, possesses a very fast rate at pH = 7.4 of 1.6 x 10(+9) M(-1) s(-1) exceeding that of the native mitochondrial MnSOD enzymes.
authors: Pharmacia Corporation (BB4M), 700 Chesterfield Parkway North, Chesterfield, Missouri 63017, USA.
authors: K
authors: K
authors: Aston
authors: N
authors: N
authors: Rath
authors: A
authors: A
authors: Naik
authors: U
authors: U
authors: Slomczynska
authors: O F
authors: OF
authors: Schall
authors: D P
authors: DP
authors: Riley
mesh_terms: D002384:Catalysis; D017076:Computer-Aided Design; D018360:Crystallography, X-Ray; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008345:Manganese / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D018716:Molecular Mimicry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D013237:Stereoisomerism; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000378:metabolism
chemical_list: D009942:Organometallic Compounds; C121876:imisopasem manganese; D008345:Manganese; D013482:Superoxide Dismutase