Bemerkungen über Thermochromie von Kobalt(II) chloridlösungen in organischen Medien, 1. Mitt.: Lösungen in verschiedenen Alkoholen

The thermochromism of solutions of cobalt(II) chloride in methanol, ethanol, n- and iso-propyl, n-, iso- and sec. butyl alcohol was studied spectrophotometrically. The blue color of these solutions fades with decreasing temperature, solutions in primary alcohols being especially variable, becoming pink at sufficiently low temperature. Solutions in secondary alcohols are, on the other hand, much less variable. The thermochromism can be ascribed, in general, to the shift of the equilibrium $$[CoL_2 Cl_2 ] + (3 - 4) L\begin{array}{*{20}c} \to \\ \leftarrow \\ \end{array} ([CoL_5 Cl]^ + or [CoL_6 ]^{2 + } ) + (1 - 2) Cl^ - $$ (L: solvent molecule). In the case of methanol, however, the two equilibria $$[CoLCl_3 ]^ - + 4 L \begin{array}{*{20}c} \to \\ \leftarrow \\ \end{array} [CoL_5 Cl]^ + + 2 Cl^ - $$ and $$[CoL_5 Cl]^ + + L\begin{array}{*{20}c} \to \\ \leftarrow \\ \end{array} [CoL_6 ]^{2 + } ) + Cl^ - $$ seem to be shifted one after another. The significance of the difference between primary and secondary alcohols is briefly discussed in connection with some related effects, i.e. the pressure effect studied byKitamura andOsugi ⁷ and the water effect found byKato et al.¹⁰.     

The electronic structure of the heptafulvalene trianion radical—The doublet instability of the Hartree-Fock solution and related phenomena

The restricted Hartree-Fock (RHF) solution for the trianion radical of heptafulvalene, obtained using the open-shell SCF formalism of the Pariser-Parr-Pople method, is found to be doublet unstable at the conventionalD _2h nuclear arrangement. We calculate the broken-symmetry charge-density wave (CDW) solution and examine its properties. It is shown that the proton hyperfine splittings for the trianion radical calculated from the CDW solution are in good agreement with the experimental values. Further, we briefly refer to the possibility of the lattice instability of the trianion radical from the fully-symmetricalD _2h to theC _2v nuclear arrangement.     

Isolation of an inclusion complex of naphthol and its benzoate as an intermediate in the solvent-free benzoylation reaction of naphthol

Solvent-free benzoylation of naphthol was found to proceed via an inclusion complex intermediate of the naphthol and its benzoate by IR spectral monitoring.     

The role of DNA hypermethylation in human neoplasia

Cancer development and progression is dictated by a series of alterations in genes such as oncogenes, tumor suppressor genes, DNA repair genes, and others. DNA methylation is an epigenetic modification that is profoundly altered in most cancers. Recently, hypermethylation of CpG-rich areas located in the promoter of genes (CpG islands) has been shown to be commonly implicated in silencing tumor suppressor genes in cancer. By cloning and characterizing a large number of such CpG islands hypermethylated in colon cancer, we found that two processes explain most of these events. Age-related CpG island methylation in a subset of cells in normal tissues, followed by intensification of methylation in cancer cells explains the majority of hypermethylation events in colon cancer and may provide a mechanistic link between aging and cancer formation. Most of the other CpG islands methylated in colon cancer can be explained by a newly described phenotype, the CpG island methylator phenotype (CIMP) which results in multiple methylation events in a subset of cancers. CIMP accounts for the majority of sporadic colon cancers characterized by microsatellite instability, as well as most tumors with k-ras mutations. Understanding further the factors that lead to, and modulate, aberrant methylation in cancer may provide novel avenues for prevention and treatment of this disease.     

One-pot assembly of tricyclo[6.2.1.0(1,6)]undecan-4-one and related polycyclic compounds by tandem electroreductive cyclization

[reaction: see text] Electroreductive tandem cyclization of 4-allyl-4-(2-bromoprop-2-en-1-yl)cyclohex-2-en-1-one to tricyclo[6.2.1.0(1,6)]undecan-4-one has been demonstrated. This protocol represents an attractive alternative to conventional tandem radical cyclization.     

The negative ion mass spectra of mixtures of sulphur and organic compounds. I—The formation of [M+Sn]− from the mixture of sulphur and dinitriles

The negative ion mass spectra of sulphur, dinitriles and their mixtures were studied. The abundance of negative ions of sulphur was almost comparable to that of positive ions. In the negative ion mass spectrum of a mixture of sulphur and dinitrile, intense and characteristic peaks of [M + S_n]^? (n = 2, 3, 4, etc.) were observed resulting from ion–molecule association of dinitrile with the S_n^? anions. As a standard sample of a negative ion mass spectrum, sulphur itself has proved useful in the lower mass region (below m/e 256: S₈^?).     

Perrottetins E,F, and G from Radula perrottetii (liverwort)--isolation,structure determination,and synthesis of perrottetin e

Perrottetin E, a cytotoxic bis(bibenzyl) ether, was isolated from $\text{Radula perrottetii}$ and its structure determined by spectroscopic methods and total synthesis. Perrottetins F and G were also isolated from the same source and fully characterized.     

The doublet instabilities of the Hartree-Fock solutions for the cation and anion radicals of fulvalene systems

The doublet instabilities of the restricted Hartree-Fock (RHF) solutions for the ion radicals of fulvalene systems, some of which have been known to show the lattice instabilities, are examined in the framework of the semiempirical SCF MO approximation. The RHF solutions for the anion radical of heptafulvalene and the cation radical of pentafulvalene are found to be doublet unstable at the conventional D_2h nuclear arrangement. We calculate the broken-symmetry charge-density-wave (CDW) solutions lower in energy than the usual symmetry-adapted RHF solutions and examine their properties. It is shown that the energy lowerings due to the CDW solutions are very small in both the ion radicals, but their density matrix elements are remarkably different from those for the symmetry-adapted RHF solutions. It is also shown that the proton hyperfine splittings for the anion radical of heptafulvalene calculated assuming the CDW solution are in good agreement with the experimental values. Finally, we refer to the relationship between the doublet instability of the RHF solution and the lattice instability.     

Occurrence of polygodial and 1-(2,4,6-trimethoxyphenyl)-but-2-en-1-one from some ferns and liverworts: role of pungent components in bryophytes and pteridophytes evolution

The New Zealand fern Blechnum fluviatile and liverwort, Hymenophyton flabellatum produce the characteristic pungent compounds, (-)-polygodial, a sesquiterpene dialdehyde, and 1-(2,4,6-trimethoxyphenyl)-but-2-en-1-one, respectively. The former compound has been isolated from the Japanese liverwort, Porella vernicosa complex and the latter one from the Japanese fern, Arachinoides standishii. The occurrence of both compounds in both pteridophytes and bryophytes provides another important link between bryophytes and ferns.