Enhancement of the Automatic Diameter Control System for the Czochralski Growth of Nd:GdVO4 Crystals

The automatic diameter control system was enhanced for the growth of Nd-doped GdVO₄ single crystals by the Czochralski method. It was estimated that excessive amount of feedback in the control system is the effective way to improve the shape of rare-earth vanadate single crystals. The spectral analysis for crystal weight and generator power signals was carried out in real time during growth process for determination of oscillations in the control system.     

Glycopolymers Mimicking GM1 Gangliosides: Cooperativity of Galactose and Neuraminic Acid for Cholera Toxin Recognition

Glycopolymers mimicking GM1 gangliosides were synthesized by incorporating multiple types of carbohydrates into the polymer backbone. The glycopolymers were immobilized onto gold surfaces, and the interactions with the cholera toxin B subunit (CTB) were analyzed using surface plasmon resonance imaging. The glycopolymer containing both galactose and neuraminic acid showed enhanced recognition of CTB. The interaction was enhanced mainly because of an improvement in the dissociation process by the binding of the neuraminic acid group in the GM1 binding pocket. This cooperativity of galactose and neuraminic acid was achieved by incorporation into the same flexible polymer backbone, and the importance of the close placement of galactose and neuraminic acid groups was revealed. These results will be valuable in medical fields and also for the development of biofunctional materials.     

Induced Circular‐Dichroism Chirality Probes for Selective Amino Acid Detection through Screening of a Dynamic Combinatorial Library of Lanthanide Complexes

A dynamic combinatorial library of lanthanide complexes was prepared to develop induced‐circular‐dichroism (CD) chirality probes. It totaled 168 combinations of coordinative N‐aromatic chromophores, trivalent lanthanide centers, and guest amino acids. Eu³⁺ and Tb³⁺ complexes prepared with quinolinecarboxylic acid were particularly effective as induced‐CD chirality probes for selective alanine detection, whereas a Yb³⁺ complex with terpyridine exhibited glutamine selectivity. The former two complexes highly preferred alanine to the corresponding amine, ester, amino alcohol, and carboxylic acid derivatives. As such, the present combinatorial screening of a dynamic lanthanide complex library has led to a new series of induced‐CD chirality probes for specific amino acids.     

Construction of Vicinal Quaternary Stereogenic Centers by Enantioselective Direct Mannich‐Type Reaction Using a Chiral Bis(guanidino)iminophosphorane Catalyst

A novel asymmetric direct Mannich‐type reaction of α‐iminophenylacetate esters with thionolactones, bearing a substituent at the α‐position, as a less acidic pronucleophile was developed. Using bis(guanidino)iminophosphorane as the chiral organosuperbase catalyst, the reaction afforded densely functionalized amino‐acid derivatives having vicinal quaternary stereogenic centers, one of which is an all‐carbon quaternary stereogenic center, in good yield with high diastereo‐ and enantioselectivities.     

Some additional aspects of versatile starting compounds for cationic organoiron complexes: molecular structure of the aqua complex [(η-C5Me4Et)Fe(CO)2(OH2)]BF4 and solution behavior of the THF complex [(η---C5R5)Fe(CO)2(THF)]BF4

The structures of the versatile starting compounds for organoiron complexes, the cationic aqua complex [(η⁵-C₅Me₄Et)Fe(CO)₂(OH₂)]BF₄ (1b) and the halide complexes (η⁵-C₅Me₅)Fe(CO)₂-I (2a), (η⁵-C₅Me₄Et)Fe(CO)₂-I (2b) and (η⁵-C₅Me₄Et)Fe(CO)₂-Cl (3b), are characterized by X-ray crystallography. Complex 1b [Fe---O: 2.022(8) Å and 2.043(9) Å, two independent molecules] is the first structurally characterized example of organoiron aqua complexes. Details of the synthetic procedures for the above complexes and the labile cationic THF complexes [η⁵-C₅R₅)Fe(CO)₂(THF)]BF₄ (4) are disclosed, and the dissociation equilibrium of 4 is confirmed by means of variable temperature ¹H-NMR as well as saturation transfer experiment.     

Evaluation of the physical stability and local crystallization of amorphous terfenadine using XRD-DSC and micro-TA

It is very difficult to follow rapid changes in polymorphic transformation and crystallization and to estimate the species recrystallized from the amorphous form. The aim of this study was to clarify the structural changes of amorphous terfenadine and to evaluate the polymorphs crystallized from amorphous samples using XRD-DSC and an atomic force microscope with a thermal probe (micro-TA). Amorphous samples were prepared by grinding or rapid cooling of the melt. The rapid structural transitions of samples were followed by the XRD-DSC system. On the DSC trace of the quenched terfenadine, two exotherms were observed, while only one exothermic peak was observed in the DSC scan of a ground sample. From the in situ data obtained by the XRD-DSC system, the stable form of terfenadine was recrystallized during heating of the ground amorphous sample, whereas the metastable form was recrystallized from the quenched amorphous sample and the crystallized polymorph changed to the stable form. Obtained data suggested that recrystallized species could be related to the homogeneity of samples. When the stored sample surface was scanned by atomic force microscopy (AFM), heterogeneous crystallization was observed. By using micro-TA, melting temperatures at various points were measured, and polymorph forms I and II were crystallized in each region. The percentages of the crystallized form I stored at 120 and 135 °C were 47 and 79%, respectively. This result suggested that increasing the storage temperature increased the crystallization of form I, the stable form, confirming the temperature dependency of the crystallized form. The crystallization behavior of amorphous drug was affected by the annealing temperature. Micro-TA would be useful for detecting the inhomogeneities in polymorphs crystallized from amorphous drug.