Entropy of planar random surfaces on the lattice

We study planar random surfaces on a hypercubic lattice in two and three dimensions by Monte Carlo techniques. Our data are consistent with the formula n₀(A;C) A^b₀A, where n₀(A;C) is the number of planar random surfaces with area A and boundary C. We find b₀ = −1.4 ± 0.2, = 5.31 ± 0.03 (for d = 2) and b₀ = −1.5 ± 0.2, = 7.13 ± 0.05 (for d = 3). The values of b₀ disagree with those obtained from the Polyakov string model.     

Study on the cell wall skeleton derived from Mycobacterium bovis BCG Tokyo 172 (SMP-105): establishment of preparation and analytical methods

Mycobacterial cell walls have diverse adjuvant activities, and in particular, cell wall skeleton (CWS) of Mycobacterium bovis BCG has been expected as a drug for tumor immunotherapy. However, its molecular structure-biological activity relationship has not been fully elucidated despite more than 30 years of intensive research. Since it is important to secure purified CWS for such investigation, we established a preparation method of CWS from M. bovis BCG Tokyo 172 (SMP-105) and developed accurate, precise, and reliable analytical methods, based on previous reports. Furthermore, we confirmed that SMP-105 is composed of mycolic acids; arabinogalactan consisting of arabinose, galactose, and rhamnose; and peptidoglycan consisting of alanine, glutamic acid, diaminopimeric acid, muramic acid, glucosamine, and galactosamine. We also determined the levels of potential impurities that might be contaminated in the original bacterium or arise during the manufacturing process, such as glucose, mannose, non-constituted amino acids, as well as nucleic acid, trehaolse di-mycolate, and bacterial endotoxins. These results demonstrated that the prepared SMP-105 was of sufficient quality for research into the chemistry, bioactivity, and structure-activity relationship of CWS.     

Development of a micropulverized extraction method for rapid toxicological analysis of methamphetamine in hair

We developed a rapid sample preparation method for the toxicological analysis of methamphetamine and amphetamine (the major metabolite of methamphetamine) in human hair by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), to facilitate fast screening and quantitation. Two milligrams of hair were mechanically micropulverized for 5 min in a 2-ml plastic tube together with 100 microl of an aqueous solvent containing 10% acetonitrile, 100 mM trifluoroacetic acid and the corresponding deuterium analogues as internal standards. The pulverizing highly disintegrated the hair components, simultaneously allowing the extraction of any drugs present in the hair. After filtering the suspension with a membrane-filter unit, the clear filtrate was directly analyzed by HPLC-MS/MS. No evaporation processes were required for sample preparation. Method optimization and validation study were carried out using real-case specimens and fortified samples in which the drugs had been artificially absorbed, respectively. Concentration ranges for quantitation were 0.040-125 and 0.040-25 ng/mg for methamphetamine and amphetamine, respectively. Real-case specimens were analyzed by the method presented here and by conventional ones to verify the applicability of our method to real-world analysis. Our method took less than 30 min for a set of chromatograms to be obtained from a washed hair sample.     

Chiral diene-phosphine tridentate ligands for rhodium-catalyzed asymmetric cycloisomerization of 1,6-enynes

Asymmetric cycloisomerization of nitrogen-bridged 1,6-enynes proceeded in the presence of a cationic rhodium complex coordinated with a chiral diene/phosphine tridentate ligand to give high yields of chiral 3-azabicyclo[4.1.0]heptenes with high enantioselectivity.     

Synthesis and characterization of small circular double-stranded RNAs

Small circular double-stranded RNAs (dsRNAs) were synthesized. The structural analysis by atomic force microscopy gave direct images for the interpretation of the structural strain present in circular dsRNAs. Finally, we demonstrated that circular dsRNA caused RNAi effect in cells.     

Z-Selective Preparation of β-Monosubstituted α,β-Unsaturated Amides Using Diphenylphosphonoacetamides

The Horner-Wadsworth-Emmons reaction of diphenylphosphonoacetamides [(PhO) 2 P(O)CH 2 CONRR'] ( 2a : R, R' = CH 2 Ph; 2b : R = CH 2 Ph, R' = H; 2c : R = Me, R' = OMe) was examined. The reaction of 2a was found to be Z -selective for benzaldehyde with selectivities up to 94:6. Reagent 2b led to reasonable selectivity for both benzaldehyde (85:15) and 3-phenylpropionaldehyde (87:13), while 2c was somewhat effective only for the latter aldehyde (83:17).     

Copper mediated defluorinative allylic alkylation of difluorohomoallyl alcohol derivatives directed to an efficient synthetic method for (Z)-fluoroalkene dipeptide isosteres

Difluoroallylation of optically pure O-silylated (S)-2-methyl-3-hydroxypropanal 10a with bromodifluoropropene mediated by indium provided the corresponding difluorohomoallyl alcohol 11a with low diastereoselectivity, but without a decrease in optical purity. Defluorinative allylic alkylation of each diastereomer of the difluorohomoallyl alcohol efficiently proceeded by the reaction with trialkylaluminium and Cu(I) system or Grignard reagent and a catalytic amount of CuI system in THF to give the fluorine-substituted allylic alcohol 12 in an high yield and in an excellent Z selective manner. Subsequent imidate Claisen rearrangement of the allylic alcohol 12 proceeded with a complete 1,3-chirality transfer to give the fluoroalkene dipeptide isostere structure 14 after the final conversion of the primary alcohol 20 into the carboxylic acid form.     

Isolation and characterization of atropisomers of seven-membered-ring benzolactams

The atropisomeric properties of seven-membered-ring benzolactams (7a-c and 8a) [1,5-benzodiazepin-2-one (a), 1,5-benzothiazepin-4-one (b), and 1-benzazepin-2-one (c)] were examined. The atropisomers were isolated as the diastereomers with an (S)-phenethylamide moiety, which were characterized by X-ray crystallography, and the barriers to their interconversion were clarified.