Synthesis of azoxybenzene-SbCl5 complexes and their selective ortho-wallach rearrangement

When an equimolar solution of various azoxybenzenes and SbCl₅ in carbon tetrachloride were mixed, a 1:1 complex immediately deposited as orange crystals in high yield. The thermal reaction of these complexes in inert solvents gives o-hydroxy-azobenzene selectively. On the contrary, other Lewis acids such as TiCl₄, AlCl₃, FeCl₃ and ZnBr₂ failed to give an isolatable complex with azoxybenzene, and their direct thermal reaction with azoxybenzene resulted in deoxygenation to yield azobenzene as a main product.     

Significance of renal high uptake in bone marrow scintigraphy with 111In-chloride

The significance of high renal uptake found in patients with hematological disease who underwent bone marrow scintigraphy with 111In-chloride was investigated. In patients with a high renal uptake, the uptake in bone marrow was low, suggesting a reflection of erythropoietic activity. The reversal relationship, however, was not necessarily present. With regard to correlation with iron metabolism, significantly higher uptake of serum Fe and lower UIBC were found among those with high renal uptake, suggesting that the level of free trans ferrin in the serum is largely involved in the high uptake in the kidney.     

Chiral bis-pi-allylpalladium complex catalyzed asymmetric allylation of imines: enhancement of the enantioselectivity and chemical yield in the presence of water

The chiral pi-allylpalladium complex 2a, prepared from exoethylidenenorpinane 7, catalyzed the allylation of diverse imines with allyltributylstannane in the presence of 1 equiv of water in good to high enantioselectivities. The catalyst prepared from a 1:1 mixture of (E)- and (Z)-7 was found to be consisting of two stereoisomers 2a and 2b in 1.3:1 ratio. On separation, 2a catalyzed the allylation of imines in much higher enantioselectivities than 2b, giving the same major enantiomer and thereby justifying the need to separate 2a free of 2b. We have achieved the highest separation ratio of >400:1 for 2a:2b by repeated recrystallizations. Isomerization of 2b to 2a during recovery of 2a from the filtrates was observed as more of 2a was recovered each time during recrystallization. Although dry THF was the best solvent, we tried various additives and found that addition of one equivalent of water gave the best results with respect to shorter reaction time, higher yields and enantioselectivities. Thus, we have developed a more general, reproducible, robust and a non-Lewis acid catalyzed procedure for catalytic asymmetric allylation of imines under essentially neutral conditions.     

Convergent total syntheses of gambierol and 16-epi-gambierol and their biological activities

The convergent total syntheses of gambierol (1) and 16-epi-gambierol (2) have been achieved. The ABC and FGH ring segments 4 and 5 were prepared from known compounds 6 and 13, respectively, by linear manners. The fragments prepared were connected by our own synthetic strategy including the intramolecular allylation of alpha-acetoxy ether followed by ring-closing metathesis to furnish the octacyclic ether 3. The diiodoalkene 45, prepared from 3, was converted to the Z-iodoalkene 50 via a novel and stereoselective hydrogenolysis followed by deprotection. Construction of the triene side chain was performed by the modified Stille coupling of 50 with the Z-vinylic stannane 41 to afford 1. The similar transformations were carried out on the epimeric octacycle 34 to give 2, which showed no toxicity against mice at the concentration of 14 mg/kg.     

Evaluation of thermoporometry for characterization of mesoporous materials

The accuracy of thermoporometry (TPM) in terms of the characterization of SBA-15 is examined based on a model that classifies the water in the mesopores into two different types: freezable pore water, which can form cylindrical ice crystals, and nonfreezable pore water, which cannot undergo a phase transition during a differential scanning calorimetry (DSC) measurement. Applying the empirical relationship between the sizes of the ice crystals formed in the mesopores and the solidification temperature of the freezable pore water to a thermogram (a recording of the heat flux during the solidification of the freezable pore water) yielded a size distribution of the ice crystals. The size of the ice crystals increased slightly with repetitive freezing, indicating that the mesopores were enlarged by formation of the ice crystals. Adding the thickness, t(nf), of the nonfreezable pore water layer to the ice crystal-size distribution calculated from the thermogram allowed for the determination of the porous properties of SBA-15. The porous properties attained from TPM experiments were compared with the results attained through the combination of Ar gas adsorption experiments and nonlocal density functional theory (NLDFT) analysis. The porous properties determined by TPM were confirmed to be quite sensitive to the t(nf) value.     

Unifying criteria for dissolution kinetics of various hydroxyapatite preparations

A powder suspension method has been used to study the dissolution rate behavior of various hydroxyapatite (HAP) preparations in acidic media containing different levels of calcium and phosphate. Despite the reported variabilities in the properties among differently prepared samples, the present study indicates that, with regard to the dissolution rate behavior, there is an important common characteristic dissolution rate component. There appears to be a dissolution site common to most HAP preparations that may be associated with the predominant surface of the HAP crystal. Also, an attempt is made to correlate the dissolution rate data with the study of Young and Holcomb on the properties of different HAP preparations.     

Luminescent palladium complexes containing thioamide-based SCS pincer ligands

Thioamide-based tridentate ligands, 1,3-benzenedicarbothioamides (1a-c), were used to afford pincer palladium(II) complexes (Pd(1-H)Cl, 2a-c) with η³-S,C,S type coordination. The complexes exhibit strong emission in a glassy frozen state as well as in the solid state. The decay lifetime of the emission from the complexes is in a range of 8-9 × 10⁻⁵ s, which is indicative of phosphorescent emission.