Nonclassical urea oligomers. IV. Polymerization of (S)-1-(N-phenyl-carbamoyl)-2-methylaziridine. A synthesis of optically active crystalline oligomer with narrow molecular weight distribution

In the presence of Et₂SO₄, (S)-1-(N-phenyl-carbamoyl)-2-methylaziridine gave an oligomer with a structure of [CH₂? CHCH₃? N(CONHPh)]_n. The oligomer has optically active isotactic configuration and narrow molecular weight distribution (DP ca. 8). The net polymerization behavior of the monomer and chemical property, such as absorptivity of Et₂SO₄, of the oligomer are analogous to the case of 1-(N-phenyl-carbamoyl)-aziridine. The ring opening occurs with retention of the configuration at the asymmetric carbon atom and the oligomer can be crystallized at around 90°C.     

Magnetic susceptibilities of UO2ZrO2 solid solutions

The magnetic susceptibility of cubic solid solutions of UO₂ and ZrO₂ with a fluorite structure has been measured from room temperature to 2.3 K. The magnetic moment and the Weiss constant have been determined in the temperature range where the Curie-Weiss law holds. These values decrease monotonically with increasing ZrO₂ concentration. The solid solutions of UO₂ diluted with 0 ～ 20 mole% ZrO₂ show an antiferromagnetic transition and have a linear dependence of Néel temperature on concentration, with a critical concentration of 78 mole% UO₂. The molecular field theory which includes next-nearest-neighbor interaction was applied to the results. The interaction between nearest-neighbor spins, J₁, decreases with increasing ZrO₂ concentration, whereas that between next-nearest-neighbor spins, J₂, increases. The behavior of J₁ against composition is thought to be caused from the direct effect of magnetic dilution with ZrO₂. Regarding the behavior of J₂, the effect of increasing magnetic interaction due to the smaller distance of uranium ions is considered to be stronger than the magnetic dilution effect.     

Total synthesis of monocyclic β-lactam antibiotics,nocardicin A and D

The total synthesis of monocyclic β-lactam antibiotics, nocardicins A (1a) and D (1d), is described. 3-Aminonocardicinic acid (3-ANA, 2) was synthesized from p-hydroxyphenylglycine via an acid chloride-imine cyloaddition reaction. The side chain amino acid 13 was prepared via a key step of condensation of p-hydroxyacetophenone and α-phthalimidobutyrolactone. Acylation of 3-ANA with 13 gave nocardicin D, from which nocardicin A was obtained by oximation.     

Copper-catalyzed acylations of o-vinylbenzylzirconocene intermediate and synthetic application toward steroid skeleton

Benzylzirconocene intermediate, which was readily prepared by a reaction of o-alkoxymethylstyrene with `Cp₂Zr' under mild conditions, reacted with acyl chlorides in the presence of a catalytic amount of CuBr-SMe₂ to give ketone derivatives in moderate to good yields.     

INDUCTION OF phr GENE EXPRESSION BY PYRIMIDINE DIMERS IN Escherichia coli

The photoreactivating enzyme (PRE) is concerned with mainly two kinds of light wavelength. The PRE splits UVC (254 nm)-induced pyrimidine dimer by absorbing UVA (320–380 nm) or visible light in its chromophore. The present paper demonstrates that the phr gene expression was efficiently induced in an excision defective strain (uvrA∼) after irradiation by UVC and UVB (290-320 nm), but not by UVA and visible light. In addition, the induced activity was significantly depressed by irradiation with UVA and visible light. Therefore we conclude that the phr gene expression can be induced by pyrimidine dimers.     

New approach to the practical synthesis of tri- or tetrasubstituted pyrimidine derivatives: a four-component coupling reaction from a functionalized silane, two types of aromatic nitriles, and acetals

[reaction: see text] A new approach to the synthesis of tri- or tetrasubstituted pyrimidines by a four-component coupling reaction using a functionalized silane, two types of aromatic nitriles, and an acetal is described. The efficient transformation of the pyrimidine framework consisting of an isoxazolyl ring and an ethoxy group to the 1,3,8-triazanaphthalene skeleton also proceeded in nearly quantitative yield.     

Generation and reaction of heteroaromatic zirconocene: synthetic application to polycyclic heterocycles

Heteroaromatic zirconocene intermediates were generated by the reaction of ‘Cp₂Zr’ with alkoxymethyl-(TMS-ethynyl)-indole, -benzofuran or -benzothiophene derivatives under mild conditions in moderate to good yields. Copper-catalyzed C-C bond formation of the zirconocene intermediate with allylic halides gave allylation products, which were transformed into heterocyclic dienes through enyne metathesis. Preliminary Diels-Alder reaction of the dienes with DMAD showed notable site selectivity.     

Toroidal Lie algebras and vertex representations

The paper describes the theory of the toroidal Lie algebra, i.e. the Lie algebra of polynomial maps of a complex torus ^××^× into a finite-dimensional simple Lie algebra g. We describe the universal central extension t of this algebra and give an abstract presentation for it in terms of generators and relations involving the extended Cartan matrix of g. Using this presentation and vertex operators we obtain a large class of integrable indecomposable representations of t in the case that g is of type A, D, or E. The submodule structure of these indecomposable modules is described in terms of the ideal structure of a suitable commutative associative algebra.To Professor J. Tits for his sixtieth birthday