Diversity of the biosynthesis of the isoprene units

This review covers the biosynthesis of the starter units of terpenoids, isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) via the nonmevalonate pathway together with a new enzyme involved in the conversion of IPP and DMAPP, i.e type 2 IPP isomerase. The biosynthesis of terpenoids produced by actinomycetes is also reviewed. 117 references are cited.     

A B3LYP study on the mechanism of second H2O formation in a fully reduced cytochrome c oxidase

The mechanism of second H₂O formation in fully reduced cytochrome c oxidase is examined by sequential additions of one electron and two protons to a [Fe(IV)O, Cu(II)] compound II, which is the final intermediate of first H₂O formation. It is found that the addition of one electron induces the concerted proton–electron transfer from the Cu_B to FeO moieties with no energy barriers. The H₂O molecule coordinating to the Cu atom is a key molecule for the proton transfer from the Cu_B moiety to the FeO and/or Fe–OH moieties. It is also found from the results in previous and the present works that one can realize the reduction process of dioxygen by fully reduced cytochrome c oxidase.     

Polycyclic N-hetero compounds. XXXV. Syntheses and anti-platelet aggregation activity of 5,6-Dihydro-4H-benzo[3,4]cyclohept[1,2-e]imidazo[1,2-c]pyrimidines with an oxygen function at the 1-position

Various 6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-d][pyrimidines bearing amino acid group at the 4-position of the skeleton were synthesized by the reaction of 4-chloro-6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-d]-pyrimidine with some amino acid, which were cyclized to 5,6-dihydro-4H-benzo[3,4]cyclohept[1,2-e]imidazo-[1,2-c]pyrimidines, corresponding to B-homo-11,13,15-triazasteroids. Their inhibitory activities against platelet aggregation induced by collagen were also investigated.     

Redox-associated eta(1) to eta(2) conversion of disulfide ligands in dinuclear ruthenium complexes

Disulfide-bridged dinuclear ruthenium complexes [[Ru(MeCN)(P(OMe)(3))(2)](2)(mu-X)(mu,eta(2)-S(2))][ZnX(3)(MeCN)] (X = Cl (2), Br (4)), [[Ru(MeCN)(P(OMe)(3))(2)](2)(mu-Cl)(2)(mu,eta(1)-S(2))](CF(3)SO(3)) (5), [[Ru(MeCN)(P(OMe)(3))(2)](2)(mu-Cl)(mu,eta(2)-S(2))](BF(4)) (6), and [[Ru(MeCN)(2)(P(OMe)(3))(2)](2)(mu-Cl)(mu,eta(1)-S(2))](CF(3)SO(3))(3) (7) were synthesized, and the crystal structures of 2 and 4 were determined. Crystal data: 2, triclinic, P1, a = 15.921(4) A, b = 17.484(4) A, c = 8.774(2) A, alpha = 103.14(2) degrees, beta = 102.30(2) degrees, gamma = 109.68(2) degrees, V = 2124(1) A(3), Z = 2, R (R(w)) = 0.055 (0.074); 4, triclinic, P1 a = 15.943(4) A, b = 17.703(4) A, c = 8.883(1) A, alpha = 102.96(2) degrees, beta = 102.02(2) degrees, gamma = 109.10(2) degrees, V = 2198.4(9) A(3), Z = 2, R (R(w)) = 0.048 (0.067). Complexes 2 and 4 were obtained by reduction of the disulfide-bridged ruthenium complexes [[RuX(P(OMe)(3))(2)](2)(mu-X)(2)(mu,eta(1)-S(2))] (X = Cl (1), Br (3)) with zinc, respectively. Complex 5 was synthesized by oxidation of 2 with AgCF(3)SO(3). Through these redox steps, the coordination mode of the disulfide ligand was converted from mu,eta(1) in 1 and 3 to mu,eta(2) in 2 and 4 and further reverted to mu,eta(1) in 5. Electrochemical studies of 6 indicated that similar conversion of the coordination mode occurs also in electrochemical redox reactions.     

Total synthesis of the disaccharide of bleomycin, 2-0-(α-D-mannopyranosyl)-L-gulopyranose

2-0-(α-$\text{D}$-Mannopyranosyl)-$\text{L}$-gulopyranose, the sugar portion of bleomycin has been synthesized.     

ESR study of radiation-induced polymerization of methyl methacrylate on solid surfaces

ESR spectra of methyl methacrylate (MMA) adsorbed on solid surfaces such as silica, alumina, and CPG-10 show a seven-line absorption due to monomer radicals when γ-irradiated at ?196°C. These spectra turn into conventional nine-line spectra by annealing at ?86°C as a result of polymerization. The intensity ratio of the four-line component to the five-line component changes with further polymerization. The ratio depends on the kind of solid and the smallest value is obtained in the spectra of alumina-MMA. The temperature of irradiation strongly affects the value in alumina-MMA. These results suggest that MMA is strongly adsorbed and deformed the conformation on alumina surface.     

Ab initio molecular orbital study on the G-selectivity of GGG triplet in copper(I)-mediated one-electron oxidation

The G-selectivity for Cu(I)-mediated one-electron oxidation of 5'-TG(1)G(2)G(3)-3' and 5'-CG(1)G(2)G(3)-3' has been examined by ab initio molecular orbital calculations. It was confirmed that G(1) is selectively damaged by Cu(I) ion for both 5'-TG(1)G(2)G(3)-3' and 5'-CG(1)G(2)G(3)-3', being good agreement with experimental results. The Cu(I)-mediated G(1)-selectivity is primarily due to the stability of the Cu(I)-coordinated complex, [-XG(1)G(2)G(3)-,-Cu(I)(H(2)O)(3)](+). The Cu(I) ion coordinates selectively to N7 of G(2) of 5'-G(1)G(2)G(3)-3' rather than N7 of G(1). The G(2)-selective coordination induces the G(1)-selective trap of a hole that is created by one-electron oxidation and migrates to GGG triplet. Therefore, the radical cation of G(1) is selectively created in both 5'-TG(1)G(2)G(3)-3' and 5'-CG(1)G(2)G(3)-3', giving the G(1)-selective damage of 5'-G(1)G(2)G(3)-3'.     

Polymerization of (p‐vinylphenyl)hydrogalvinoxyl and formation of a stable polyradical derivative

4‐[(3,5‐Di‐tert‐butyl‐4‐hydroxyphenyl)(3,5‐di‐tert‐butyl‐4‐oxo‐cyclohexa‐ 2,5‐dienylidene)methyl]styrene (abbreviated as (p‐vinylphenyl)hydrogalvinoxyl) was polymerized using AIBN as an initiator to give a bright yellow polymer with M w = 3.2 × 10⁴. The polymer was oxidized to give the corresponding polyradical derivative, whose spin concentration could be increased up to about 70 mol % depending on oxidative conditions. ESR signal line‐width in the solid state was greatly increased below 200 K for the polyradical with a high spin concentration (> 50 mol %). The magnetization and magnetic susceptibility indicated weak antiferromagnetic interaction among the radical sites. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 189–198, 1999     

Iron(II) and nickel(II) mixed-ligand complexes containing 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline

Two types of mixed-ligand complexes, i.e. [M(phen)2 (dip)]2+ and [M(phen)(dip)2]2+ (M = iron(II) and nickel(II); phen = 1,10-phenanthroline and dip = 4,7-diphenyl-1,10-phenanthroline) have been prepared from their related tris-complexes, [M(phen)3]2+ by ligand substitution, and isolated by semi-preparative HPLC. Elemental and chromatographic analyses confirm the purity of the isolated complexes while u.v./vis and i.r. spectra were used to identify and characterize them. 1H-n.m.r. and room temperature Mössbauer spectra of the iron(III) complexes were also measured and the results are discussed. In addition, our preliminary results on hypochromicity in the MLCT band and circular dihroism (CD) emerging in the u.v./vis region upon addition of CT(calf thymus)-DNA to the racemic complexes indicated that the iron(II) mixed-ligand complexes interact with CT-DNA.     

Novel photosensitive polymer based on polycarbodiimide and photoamine generator

A novel photosensitive polymer based on end‐capped polycarbodiimide (E‐PCD) and the photoamine generator N‐{[(4,5‐dimethoxy‐2‐nitrobenzyl)oxy]carbonyl}‐2,6‐dimethylpiperidine (1) was developed. The E‐PCD was prepared by polycondensation of tolylene‐2,4‐diisocyanate in the presence of 3‐methy‐1‐phenyl‐2‐phospholene‐1‐oxide as a catalyst. The reaction of carbodiimide and secondary amine was studied. The nucleophilic addition of amine to the carbodiimide moiety proceeded smoothly and provided a guanidine base that acted as a crosslinking agent. A lithographic evaluation of the system of E‐PCD and 1 revealed that the dissolution rate of the exposed area after the postexposure bake decreased drastically, although no obvious change of the dissolution rate in the unexposed area was observed. The E‐PCD containing 10 wt % 1 functioned as a negative working photosensitive polymer when it was exposed to 365‐nm UV light, postbaked at 120 °C for 5 min, and developed with toluene at 25 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 329–336, 2000