Total Synthesis of Dictyodendrins by the Gold-Catalyzed Cascade Cyclization of Conjugated Diynes with Pyrroles

In total and formal syntheses of dictyodendrins B, C, E, and F, the key step involved the direct construction of the pyrrolo[2,3-c]carbazole core by the gold-catalyzed annulation of a conjugated diyne with a pyrrole to form three bonds and two aromatic rings. The subsequent introduction of substituents at the C1 (Suzuki–Miyaura coupling), C2 (addition to an aldehyde), N3 (alkylation), and C5 positions (Ullman coupling) provided divergent access to dictyodendrins.     

Simple and efficient fabrication of room temperature stable electride: melt-solidification and glass ceramics

Electrides are ionic compounds in which electrons act as anions. These compounds are expected to have interesting properties arising from their exotic structure. The fatal drawbacks of the thermal and chemical instability of organic electrides were resolved by the synthesis of a room temperature (RT) stable electride using single crystalline 12CaO.7Al2O3 (C12A7) with a nanoporous structure and the chemical treatments for a long duration. However, an innovative fabrication method is obviously required for practical applications such as cold electron-emitter and thermionic devices. Herein we report a simple synthesis for polycrystalline C12A7 electrides with a moderate electronic conductivity via a strongly reducing C12A7 "melt", i.e., direct solidification of the melt or crystallization of the transparent glass. Generation of carrier electrons and precipitation of the C12A7 phase from the strongly reducing melt and glass are likely associated with the incorporation of carbon-related anions for stabilizing the C12A7 phase and keeping the mobile electrons in C12A7. These findings will be broadly utilized for applications by mass production in a desired shape and dimension, facilitating the research of electrides.     

On R∞ and Q∞-manifolds

We give a characterization of manifolds modeled on $\text{R}{}^{\mathrm{\infty }}\text{= dir lim}$ or $\text{R}{}^{\mathrm{n}}\text{Q}{}^{\mathrm{\infty }}\text{=dir lim Q}{}^{\mathrm{n}}$, where Q is the Hilbert cube, and elementary short proofs of the Open Embedding Theorem for these manifolds and the following theorem generalizing the Stability Theorem: Each fine homotopy equivalence between these manifolds is a near homeomorphism. Moreover we establish the Open Embedding Approximation Theorem.     

Phase isomerism in gear-shaped molecules

The concept of new stereoisomerism due to different phase relations between the labeled cogs in a smoothly geared molecule is described.     

Structure-activity relationship study of leucinostatin A,a modulator of tumor−stroma interaction

Structure-activity relationship study of leucinostatin A, a natural nonapeptide, was performed to gain insight into the structural requirements for leucinostatin A to exhibit antiproliferative activity against DU-145 prostate cancer cells under cocultured conditions with the corresponding stromal cells. Twenty truncated peptide analogs of leucinostatin A revealed that the nonapeptide structure as a whole is essential for the biological activity. Alanine scanning demonstrated the importance of some of the amino acid components, including hydroxyleucine and the second leucine from the N-terminus. Two of the three aminoisobutyric acids could be substituted with one of the enantiomers of alanine, clearly demonstrating that each methyl group in these portions has a distinct influence on the growth-inhibitory activity.     

Formation of amorphous Mn-Bi films and their crystallization process

Mn-Bi alloy films were prepared by simultaneous vacuum deposition at liquid N₂ temperature and their structures were investigated by transmission electron microscopy and electron diffraction. Films with compositions in the range of 34 to 63 at% Mn have the Bi lattice structure at room temperature. Films with composition in the range of 68 to 95 at% Mn show diffuse haloes at room temperature. When they are heated above room temperature, those in the range of 70 to 85 at% Mn show nucleation and grain growth crystallization, whereas the films of 68 and 95 at% Mn show only grain growth crystallization. The films in the range of 70 to 85 at% Mn are concluded to be amorphous at low and at room temperature. Some of the crystals obtained by nucleation and the grain growth crystallization grow as large as 10 μm in length. Their diffraction patterns are not ascribable to reported crystals in this alloy system.     

The first example for cycloenantiomeric hexahomooxacali

Cycloenantiomeric hexahomooxacalix[3]arenes with different substituents on the three upper rims were synthesized for the first time by fixing their conformation into a cone. A cycloenantiomeric hexahomooxacalix[3]arene 6 was resolved into both enantiomeric forms and chiroptically characterized. Preliminary 1H-NMR studies indicated that the optically resolved cycloenantiomer 6 could discriminate the enantiomers of hydrochloride of phenylalanine ethyl ester.     

Preparation of new chiral building blocks via asymmetric catalysis

Highly enantio- and stereoselective preparation of some new chiral building blocks with baker's yeast or the CBS catalyst is described.     

Practical synthesis of L-erythro- and L-threo-4-fluoroglutamic acids using aminoacylase

Enantiomerically pure L-erythro- and L-threo-4-fluoroglutamic acids 1a and 1b were conveniently prepared. The key steps in this synthesis relied upon separation of diastereomers of N-chloroacetyl-4-fluoroglutamic acid 5-methyl ester 7 by recrystallization and enzymatic resolution of enantiomers of the resulting 7(a+c) and 7(b+d) by aminoacylase. Protection of the γ-carboxyl group as a methyl ester was found to be crucial for this enzymatic reaction.     

Magnetic structure of V5S8

The magnetic structure of V₅S₈ has been investigated by neutron diffraction at low temperature. Two single crystals (sample 1 and sample 2) grown by the same procedure gave considerably different results. Sample 1 was found to have an incommensurate structure, while sample 2 was found to have simple collinear antiferromagnetic structure consistent with magnetic measurements. Although the positions of the magnetic diffraction peaks of sample 1 were close to those of sample 2, the neutron intensity behavior was quite different and the detailed structure could not be determined in the case of sample 1. In both samples, the magnitude of the moments was evaluated to be much larger than the value estimated from NMR.