Modeling the active sites of bacteriophage T7 lysozyme, bovine 5-aminolevulinate dehydratase, and peptide deformylase: synthesis and structural characterization of a bis(pyrazolyl)(thioalkoxy)hydroborato zinc complex, [(Ph₂CHS)Bp^But,Pri]ZnI

Abstract

Insertion of thiobenzophenone into a B–H bond of [Bp^But,Pri]ZnI achieves the synthesis of [(Ph₂CHS)Bp^But,Pri]ZnI, a complex in which the in situ generated [NNS] donor ligand models the binding of the histidine and cysteine residues at the active sites of bacteriophage T7 lysozyme, bovine 5-aminolevulinate dehydratase and peptide deformylase.

References

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13. [Bp^But,Pri]ZnI is obtained by reaction of ZnI₂ with Tl[Bp^But,Pri](C. Dowling, P. Ghosh and G. Parkin, Polyhedron, 1997, 16, 3469).
14. [(Ph₂CHS)Bp^But,Pri]ZnI·0.5C₇H₈ is monoclinic, P2₁/c(no. 14), a= 20.474(2), b= 9.228(1), c= 20.785(2)Å, β= 90.767(6)°, U= 3926.4(7)ų, and Z= 4. CCDC 182/718.
15. Selected bond lengths in T7 lysozyme: 2.52 Å[Zn–N(His-17)], 2.67 Å[Zn–N(His-122)] and 2.15 Å[Zn–S(Cys-130)]. See ref. 10.
16. Selected bond lengths (EXAFS) in bovine 5-aminolevulinate dehydratase: 2.05 Å[Zn–N(His)], 2.05 Å[Zn–N(His)] and 2.32 Å[Zn–S(Cys)]. See ref. 11.
17. U. Brand and H. Vahrenkamp, Inorg. Chem., 1995, 34, 3285.
18. Likewise, N-(2-mercaptophenyl)picolylamine has not yielded monomeric [NNS]ZnX complexes that have been structurally characterized. See: U. Brand and H. Vahrenkamp, Chem. Ber., 1996, 129, 435.
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20. Copper and tungsten derivatives of related [(RS)Bp^RR'] ligands, namely [(p-TolS)Bp^Me₂]CuSR^20a and [(p-TolCH₂S)Bp]Mo(CO)₂(η²-S₂CR),^20b have also been reported, although they have not been structurally characterized. (a) J. S. Thompson, J. L. Zitmann, T. J. Marks and J. A. Ibers, Inorg. Chim. Acta, 1980, 46, L101; (b) A. F. Hill and J. M. Malget, J. Chem. Soc., Dalton Trans., 1997, 2003.
21. [(Ph₂CHO)Bp^But,Pri]ZnI is orthorhombic, Pca2₁(no. 36), a= 10.826(2), b= 16.378(3), c= 19.729(4)Å, U= 3498(1)ų and Z= 4. CCDC 182/718.
22. It is also worth noting that barriers to rotation follow a similar trend. For example, rotation about the B–O bond in R₂BOR' complexes is more facile than rotation about the B–S bond in R₂BSR'. See: M. T. Ashby and N. A. Sheshtawy, Organometallics, 1994, 13, 236.
23. For a brief review on dynamic NMR spectroscopy, see: G. Binsch and H. Kessler, Angew. Chem., Int. Ed. Engl., 1980, 19, 411.
24. The enthalpy and entropy of activation are: ΔH^‡= 9(1)kcal mol^–1 and ΔS^‡=– 19(5) cal K^–1 mol^–1.
25. For other examples of inversion that have been studied by dynamic NMR spectroscopy, see: E. W. Abel, S. K. Bhargava and K. G. Orrell, Prog. Inorg. Chem., 1984, 32, 1.
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