Synthesis of (±)-lineatin,the unique tricyclic pheromone of Trypodendron lineatum (olivier)

(+-)-3,3,7-Trimethyl-2,9-dioxatricyclo[4.2.1.0^{4, 7}]noname

and (+-)-3,3,7-trimethyl-2,9-dioxatricyclo[3.3.1.0^{4, 7}] nonane

were synthesized. The latter was shown to be (+-)-lineatin, an ambrosia beetle pheromone.     

Selective growth of ag nanowires on Si(111) surfaces by electroless deposition

Electroless deposition of Ag on atomically flat H-terminated Si(111) surfaces in aqueous alkaline solutions containing Ag ions produced two different sizes of Ag nanowires along atomic step edges: (1) a narrow nanowire of 10 nm in width and 0.5 nm in height and (2) a wide nanowire of 35 nm in width and 11 nm in height. The narrow and wide nanowires were formed by immersion in the solutions containing less than 1 ppb and 8 ppm dissolved-oxygen concentrations, respectively. This result indicates that the dissolved oxygen initiates the formation of Ag nucleation sites and that the fabrication method has a possibility of controlling the size of Ag nanowires.     

Synthesis and characterization of 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids with a branched-acyl chain

We previously reported the chemical synthesis of a series of novel monoacylated vitamin C derivatives, 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids (6-Acyl-AA-2G) possessing a straight-acyl chain of varying length from C(4) to C(18), as effective skin antioxidants. In this paper, we describe branched type of 6-Acyl-AA-2G derivatives (6-bAcyl-AA-2G) synthesized by use of a 2-branched-chain fatty acid anhydride as an acyl donor. The stability of 6-bAcyl-AA-2G in neutral solution was much higher than that of 6-Acyl-AA-2G, while they were susceptible to enzymatic hydrolysis for exerting vitamin C effect. These branched derivatives as well as 6-Acyl-AA-2G increased the radical scavenging activity against 1, 1-diphenyl-2-picrylhydrazyl and the lipophilicity in octanol/water-partitioning systems with increasing length of their acyl group. In addition, the 6-bAcyl-AA-2G derivative with an acyl chain of C(12), 6-bDode-AA-2G had the excellent solubility to various solvents, suggesting easy handling in cosmetic use. These characteristics of 6-bAcyl-AA-2G may be available for skin care application as an effective antioxidant.     

New synthesis of 5-amino-5-deazaflavin derivatives by direct coupling of 5-deazaflavins and amines

5-Amino-5-deazaflavin derivatives are newly synthesized by direct coupling of 5-deazaflavins and amines. Some of them revealed potential activity toward tumor cells such as L1210 or KB cells.     

A lithiation approach to cordycepin analogues variously substituted at the C-8 position

Several 8-substituted cordycepins were prepared via LDA lithiation of 2′,5′-bis-O-(t-butyldimethylsilyl)-cordycepin and successive reactions of its C-8 lithiated species with various types of electrophiles. Wittig reaction of the 8-formyl derivative was also examined.     

Effect of oral pretreatment with antibiotics on the hydrolysis of salicylic acid-tyrosine and salicylic acid-methionine prodrugs in rabbit intestinal microorganisms.

We examined the hydrolysis mechanism of salicylic acid-tyrosine (salicyl-tyrosine) and salicylic acid-methionine conjugate (salicyl-methionine) in rabbits by exploring their behavior following intraduodenal and intracecal administration (72 and 36 mumol/kg, respectively: salicylic acid equivalent). A large amount of salicyl-methionine was absorbed following intraduodenal administration of salicyl-methionine, without being metabolized to salicylic acid in the small intestinal mucosa. On the contrary, salicylic acid was detected in the blood following intraduodenal administration of salicyl-tyrosine, suggesting that salicyl-tyrosine was metabolized in the small intestinal mucosa. After oral pretreatment of rabbits with kanamycin sulfate (6 x 400 mg) or tinidazole (6 x 160 mg), the hydrolysis of salicyl-tyrosine and salicyl-methionine following intracecal administration was inhibited significantly, indicating that the intestinal microorganisms were responsible for the biotransformation of these prodrugs. Furthermore, in rabbits orally pretreated with both kanamycin sulfate and tinidazole, a significant inhibition of salicylic acid formation from salicyl-tyrosine and salicyl-methionine following intracecal administration was observed.     

Studies of the polymerization of diallyl compounds. XXII. Polymerization of diallyl oxalate in the evolution of carbon dioxide at elevated temperatures

The polymerization of diallyl oxalate was conducted in the presence of radical initiators at a high temperature range of 80–180°C; a large decrease in degree of polymerization, an increase in residual unsaturation of the resulting polymer, and the evolution of carbon dioxide were observed with the elevation of temperature. These findings were reasonably interpreted by considering the dismutation of the uncyclized growing radical to yield the allyl radical, carbon dioxide, and polymer carrying a terminal double bond. The kinetics of the polymerization of diallyl oxalate in the evolution of carbon dioxide at elevated temperatures were also discussed in detail.     

Layer-by-layer assembled multilayer films of titanate nanotubes, Ag- or Au-loaded nanotubes, and nanotubes/nanosheets with polycations

Aqueous suspensions of hydrothermally synthesized titanate nanotubes and poly(diallyldimethylammonium chloride) (PDDA) have been employed to fabricate multilayer films on various substrates in a layer-by-layer fashion. Atomic force microscopy displays the dense coverage of the substrate surface by the nanotubes. UV-vis absorption spectroscopy confirms the consecutive growth of PDDA/nanotube layer pairs. Single crystalline Ag and Au nanoparticles with narrow size distribution spatially correlating with the nanotubes have been obtained by treating the nanotubes with AgNO(3) or HAuCl(4) aqueous solution followed by chemical reduction. The noble metal nanoparticles show a strong surface plasmon absorption band. A multilayer film construction of the noble-metal-loaded nanotubes has also been achieved. This process has been further extended to the heteroassembly of nanotubes/nanosheets in different layer sequences.