The calculations of a C–H bond activation were carried out with a two-layer ONIOM (MO:MM) method using DREIDING for the low layer and density functional theory (DFT) at the B3LYP level for the high layer. One of the calculated elementary reactions was that from (C5Me5)Ru(μ-CH2=CH2)(μ-H)2Ru(C5Me5) (4) to (C5Me5)Ru(μ-CH=CH2)(H)(μ-H)2Ru(C5Me5) (5) (eq 2) and the other was that from (C5Me5)Ru(C2H5)(μ-CH2=CH2)(μ-H)Ru (C5Me5) (6) to (C5Me5)Ru(C2H5)(μ-CH=CH2)(H)(μ-H)Ru(C5Me5) (7) (eq 3). All the optimized geometries were consistent with the intermediates in keeping with the phenomenon of "bimetallic activation" reaction where the two metal centers work concertedly in a reaction. The activation free energies of eqs 2 and 3 were 18.8 and 6.9 kcal/mol, respectively. The calculations of two types of C–H bond activation pathways that respectively contain eqs 2 and 3 were carried out. These results suggested that the pathway containing eq 3 was suitable.
On the basis of restricted subduced cycle indices with chirality fittingness (RSCI-CFs), the restricted-fixed-point-matrix (RFPM) method has been developed as a new method for the combinatorial enumeration of sterically hindered derivatives of a given skeleton. Such RSCI-CFs are derived from subduced cycle indices with chirality fittingness (SCI-CFs) defined in the unit-subduced-cycle-index (USCI) approach (S. Fujita, "Symmetry and Combinatorial Enumeration in Chemistry," Springer-Verlag (1991)). Thus, the SCI-CFs are combined with territory indicators to give territory discriminants, which are treated by considering a restriction condition that rejects the occupation of any adjacent sites, so as to generate RSCI-CFs. The resulting RSCI-CFs are used to evaluate marks (the numbers of fixed points) in place of the original SCI-CFs and combined with the fixed-point-matrix (FPM) method of the USCI approach to develop the RFPM method. The RFPV method based on RSCI-CFs is applied to enumeration of sterically hindered derivatives of dodecahedrane.
The restricted-partial-cycle-index (RPCI) method for combinatorial enumeration under the restriction of no adjacency of ligands has been developed as a restricted version of the partial-cycle-index (PCI) method of the unit-subduced-cycle-index (USCI) approach (S. Fujita, "Symmetry and Combinatorial Enumeration in Chemistry," Springer-Verlag (1991)). To take account of the restriction condition, (unrestricted) subduced cycle indices with chirality fittingness (SCI-CFs) of the USCI approach are converted into restricted subduced cycle indices with chirality fittingness (RSCI-CFs). Then, restricted partial cycle indices with chirality fittingness (RPCI-CFs) are derived from the RSCI-CFs, just as partial cycle indices with chirality fittingness (PCI-CFs) are derived from the SCI-CFs in the USCI approach. The resulting RPCI-CFs provide generating functions for restricted enumerations. The RPCI method using such RPCI-CFs is applied to enumeration of dodecahedrane derivatives under the restriction of no adjacency of ligands. Several enumerated derivatives are depicted and their symmetries are discussed to comprehend stereochemical properties such as pseudoasymmetry, sphericity, and prochirality.
Chalcones and the related α,β-unsaturated ketones were studied to discover their inhibitory activities for tumor necrosis factor-α (TNF-α) and nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW264 macrophages and their molecular orbital energies. The simple α,β-enone, 1-penten-3-one (6), showed the activities stronger than or comparable to those of the phenyl-conjugated α,β-enones including natural chalcones, suggesting that the α,β-enone structure in 6 is enough to induce the above inhibition. The correlation between the inhibitory activities and the frontier molecular orbital energies suggests that (1) the enones primarily act as Michael acceptors in the inhibition with high susceptibility to the steric hindrance from their molecular structures, and (2) a possibility remains that the phenyl-conjugated enones and those with phenolic hydroxy groups act as electron-donating agents in the inflammatory process. Thus, the α,β-enone core singly suppresses the TNF-α and NO production in LPS-stimulated macrophages, but the conjugated hydroxyphenyl rings in chalcones are also important for their pharmacological activity.