Studies on antiatherosclerotic agents. Synthesis of 5-substituted derivatives of 7-ethoxycarbonyl-6,8-dimethyl-1(2H)-phthalazinone.off.

Several 5-substituted derivatives of 7-ethoxycarbonyl-6,8-dimethyl-1(2H)- phthalazinone were prepared by means of nitration, reductive amination, and diazonium decomposition. The substituents introduced included NO2, NH2, F, Cl, CN. Among the derivatives, the fluorine compound was obtained only in poor yield because intramolecular cyclization occurred predominantly.     

Interpreting Kullback-Leibler divergence with the Neyman-Pearson lemma

Kullback-Leibler divergence and the Neyman-Pearson lemma are two fundamental concepts in statistics. Both are about likelihood ratios: Kullback-Leibler divergence is the expected log-likelihood ratio, and the Neyman-Pearson lemma is about error rates of likelihood ratio tests. Exploring this connection gives another statistical interpretation of the Kullback-Leibler divergence in terms of the loss of power of the likelihood ratio test when the wrong distribution is used for one of the hypotheses. In this interpretation, the standard non-negativity property of the Kullback-Leibler divergence is essentially a restatement of the optimal property of likelihood ratios established by the Neyman-Pearson lemma. The asymmetry of Kullback-Leibler divergence is overviewed in information geometry.     

Fragmentation in doubly charged ion mass spectra of anhydropisatin and related compounds

The doubly charged ion mass spectra of anhydropisatin, 4-methoxyanhydropisatin, 3, 8, 9-trimethoxypterocarpen and 3, 4, 8, 9-tetramethoxypterocarpen were determined, and the fragmentation was explained by assuming that the paired electrons were partially localized in the fragmentations and by comparing the spectra with that of 3-(CD₃)-anhydropisatin. Conventional mass spectra of these compounds were very simple, but the doubly charged ion spectra were sufficiently characteristic for the reliable identification.     

Multi‐input–Multi‐output Molecular Response System Based on Dynamic Redox Behavior of Hexaphenylethane‐type Electron Donors with the Tetrahydrophenanthrazepine Skeleton: Strong Chiroptical Signals through the Transmission of Point Chirality to Helicity

The title heterocyclic donors undergo reversible C? C bond formation/cleavage upon electron transfer (dynamic redox behavior). The helical sense in both neutral and cationic states is interconvertible by facile ring flipping. The π‐type asymmetric center on the azepine nitrogen atom induces a significant degree of diasteromeric preference, thus endowing strong CD activity based on exciton coupling. Chiroptical properties could be modified not only by redox reactions but also by heat and protonation. The present redox pairs can serve as unprecedented three‐way‐input (e, H⁺, Δ) and two‐way‐output (UV/Vis, CD) response systems.     

Importance of the isopropylidene terminal of geranylgeranyl group for the formation of tetraether lipid in methanogenic archaea

Labeling experiments using several deuterated lipids were pursued to study the biosynthesis of macrocyclic isoprenoidal lipids of thermophilic methanogenic archaea, Methanothermobacter thermautotrophicus. The isopropylidene terminal of geranylgeranyl group of monomeric precursor appeared to be important for the CC bond formation at the hydrophobic end in the macrocyclic lipids. A mechanism involving a radical trigger at the allylic methyl group is proposed for this CC bond formation.     

UV-Vis, NMR, and time-resolved spectroscopy analysis of photoisomerization behavior of three- and six-azobenzene-bound tris(bipyridine)cobalt complexes

The photoisomerization properties of tris(bipyridine)cobalt complexes containing six or three azobenzene moieties, namely, [Co(II)(dmAB)3](BF4)2 [dmAB = 4,4'-bis[3'-(4'-tolylazo)phenyl]-2,2'-bipyridine], [Co(III)(dmAB)3](BF4)3, [Co(II)(mAB)3](BF4)2 [mAB = 4-[3' '-(4' '-tolylazo)phenyl]-2,2'-bipyridine], and [Co(III)(dmAB)3](BF4)3, derived from the effect of gathering azobenzenes in one molecule and the effect of the cobalt(II) or cobalt(III) ion were investigated using UV-vis absorption spectroscopy, femtosecond transient spectroscopy, and 1H NMR spectroscopy. In the photostationary state of these four complexes, nearly 50% of the trans-azobenzene moieties of the Co(II) complexes were converted to the cis isomer, and nearly 10% of the trans-azobenzene moieties of the Co(III) complexes isomerized to the cis isomer, implying that the cis isomer ratio in the photostationary state upon irradiation at 365 nm is controlled not by the number of azobenzene moieties in one molecule but rather by the oxidation state of the cobalt ions. The femtosecond transient absorption spectra of the ligands and the complexes suggested that the photoexcited states of the azobenzene moieties in the Co(III) complexes were strongly deactivated by electron transfer from the azobenzene moiety to the cobalt center to form an azobenzene radical cation and a Co(II) center. The cooperation among the photochemical structural changes of six azobenzene moieties in [Co(II)(dmAB)3](BF4)2 was investigated with 1H NMR spectroscopy. The time-course change in the 1H NMR signals of the methyl protons indicated that each azobenzene moiety in [Co(II)(dmAB)3](BF4)2 isomerized to a cis isomer with a random probability of 50% and without interactions among the azobenzene moieties.     

Generation of 6-(Trifluoromethyl)-4,5-dihydro-2(3H)-pyridone and the Application to Synthesis of Some Fused Nitrogen Heterocycles Carrying a Trifluoromethyl Group on the Bridgehead Position via Radical Cyclization of Dihydropyridones

Staudinger/aza-Wittig reaction of 6,6,6-trifluoro-5-oxohexanoyl azide with PPh(3) or PBu(3) was examined. A reactive intermediate acyl imine 1 was trapped by methanol. Without nucleophile, isomerized enamide form 3 was obtained. N-Iodobenzoylation and N-haloalkylation of 3 and following radical cyclization via the 5-exo or 6-exo mode gave benzoindolizidinone, indolizidinone, and quinolizidinone derivatives 10-14, which have a trifluoromethyl group at the bridgehead position adjacent to nitrogen. Although LiAlH(4) reduction of 10 and 11 gave a mixture of saturated benzoindolizidine 15 and amino alcohol 16, reduction with BH(3)/THF selectively gave the desired 15 and indolizidine 17 from 13.