Copolymerization of anhydroglucose and anhydromannose derivatives: Structure,reactivity, and conformational analyses

Phosphorus pentafluoride-catalyzed copolymerization of 1,6-anhydro-2,3,4-tri-O-(p-methylbenzyl)-β-D -glucopyranose (TXGL, monomer G) and 1,6-anhydro-2,3,4-tri-O-benzyl-β-D -mannopyranose (TBMN, monomer M) appears to follow classical copolymerization theory. Reactivity ratios calculated by the procedure of Mayo and Lewis were r_G = 0.90 ± 0.08, r_M = 11.5 ± 0.80, from which sequence distributions were calculated. A conformational analysis of anhydro sugar polymerization is presented to explain differences in reactivity of monomers and their derived cations in polymerization and copolymerization. The polymers and copolymers were characterized by viscosity, ¹H- and ¹³C-NMR spectroscopy, optical rotation, and circular dichroism. The reaction gives stereoregular polymers as have other polymerizations and copolymerizations of this class.     

Microbiological synthesis of 16-ketopregnanes from steroidal sapogenins

Incubation of diosgenone (1, 25D-spirost-4-en-3-one) with Verticillium theobromae (Turconi) Mason et Hughes (CBS) afforded 20α-hydroxypregn-4<ne-3,16-dione (3) and 3α,11β,20α-trihydroxy-5α-pregnan-16-one (4). The same transformation products were also obtained by the use of Stachylidium bicolor Link (IFO 6647). Isolation and identification processes of the products are discussed.     

220-MHz NMR spectra of acrylic monomer–2-substituted 1,3-diolefin alternating copolymers

An investigation by 220-MHz NMR spectroscopy was carried out on the alternating copolymers of acrylic monomer with 2-substituted 1,3-diolefin. The chain structures were determined. The acrylic monomers used were methyl methacrylate (MMA), acrylonitrile (AN), and methacrylonitrile (MAN); isoprene (IP) and chloroprene (CLP) were the 1,3-diolefins. In the MAN–IP alternating copolymer, the 1-position methylene protons of IP showed an AB quartet peak, confirming the α-1 linkage structure. Similarly, in the MMA–CLP and AN–CLP copolymers, the 1-position methylene protons of CLP showed and AB quartet and an ABX pattern, respectively, confirming the α-1 linkage structure in both these cases also. The α-1 linkage structure was also revealed by the decoupling technique in the MAN–CLP alternating copolymer. The AN–IP and MMA–IP alternating copolymers also possess a bond between the α-position of the acrylic monomer and the 1-position of IP. The monomeric units in the alternating copolymers of acrylic monomers with 2-substituted 1,3-diolefins were generally linked at the α-position of acrylic monomer and the 1-position of 1,3-diolefin. On the other hand, in the Diels-Alder adducts of acrylic monomer with 2-substituted 1,3-diolefin, the reaction takes place between the α-position of acrylic monomer and the 4-position of 1,3-diolefin. The regioselectivity of the alternating copolymers and the Diels-Alder adducts is quite compatible with the expectations from molecular orbital theory.     

Isolation,chemical characterization and structure of ansamitocin,a new antitumor ansamycin antibiotic

In this paper we report the isolation, chemical characterization and structural elucidation of Ansamitocin, a new antitumor antibiotic obtained from Nocardia No. C-15003 (N-1). Ansamitocin P-3, P-3' and P-4 with molecular formulae C₃₂H₄₃ClN₂O₉, C₃₂H₄₃ClN₂O₉ and C₃₃H₄₅ClN₂O₉, respectively, were identified as novel antibiotics. Their UV spectra resemble that of maytansine obtained from a plant source. Analysis of the PMR spectrum and spin-decoup studies of P-3 demonstrated that its skeletal structure was the same as that of maytansine. Reductive cleavage of each antibiotic gave maytansinol (P-0). Alkali hydrolysis of P-3, P-3' and P-4 gave isobutyric, butyric and isovaleric acids, respectively. P-3, P-3' and P-4 were concluded to be the isobutyrate, butyrate and isovalerate ester of maytansinol at C-3, respectively. An antitumor plant product, maytanacine, and its semisynthetic derivative, maytansinol propionate, were also produced by the same strain.     

DNA topology on an increase in positive writhing number of DNA: conformation changes in the time course of cis-diamminedichloroplatinum(II)-DNA adducts

We show that the topological significance of the gel mobility of cis-diamminedichloroplatinum(II) (DDP)-closed circular DNA (ccDNA) adducts decreases with reaction time, until a point at which it joins relaxed DNA, and that the mobility of the adducts increases again. There is no relationship between the relative length of the adducts and the gel mobility. Although the significance of the decrease of gel mobility is due to the unwinding of cis-DDP-DNA (or trans-DDP-DNA) adducts, the conformational significance of the subsequent increase in mobility is unclear. To elucidate the conformational significance for unwinding of the adducts, we measured the writhing number (Wk) of the adducts using electron microscopy and analyzed the topological states of cis-DDP (or trans-DDP) adducts based on the White rule, Lk=Wk+Tk. Where, Lk and Tk represent the linking and twisting number in the ring, respectively. From the data, we found that the Wk of cis-DDP-ccDNA adducts in comparison with trans-DDP-ccDNA adducts increases from a negative to a positive number with time. This suggests that cis-DDP plays a role in the change of the topological state of ccDNA. In the abstraction of platinum from the adducts with CN- ion, the differences in both topological states may explain why Pt in trans-DDP is abstracted more easily than in cis-DDP. To explain the abstraction of Pt ion, we also discuss the findings based on the thermodynamic cycle in a intermolecular crosslink model Pt(NH3)2(guanine)2(2+)-->Pt(CN)4(2-) using the Pt parametrized PM3 method.     

Imaging of the bronchial blood flow usingg RI-angiography--study on its procedure and application of dual radioisotope technique (author's transl)

RI-angiography with 99mTcO4- was carried out using a scintillation camera with a digital minicomputer for the purpose of imaging of bronchial blood flow in various lung diseases, and as application of dual radioisotope techniques, other imagings such as tumor imaging with 197HgCl2 or 67Ga-citrate and/or perfusion imaging with 99mTc-MAA, were performed simultaneously in patients remaining the same position, too. The image as a iso-count map extracted out of the image of 197HgCl2, 67Ga-citrate or 99mTc-MAA, was superimposed to the brightness image of RI-anigogram (aortic phase). By these procedures, the image of bronchial blood flow were obtained in some patients with lung cancer, pulmonary tuberculosis, lung abscess, and chronic bronchitis. The dual radioisotope techniques using RI-angiography and the other imaging were useful to make isotope diagnosis of lung diseases more reliable, and the image superimposition methods using RI-angiogram and the image of tumor or perfusion, were useful to improve anatomic orientation of the former.     

CFD simulation and analysis of emulsion droplet formation from straight-through microchannels

We recently proposed a technique for preparing monodisperse emulsions with a coefficient of variation below 5% from a silicon array of micrometer-sized channels perpendicular to the plate surface, named a straight-through microchannel (MC). This study involved three-dimensional computational fluid dynamics (CFD) simulations to calculate the formation of an oil-in-water (O/W) emulsion droplet from straight-through MCs with circular and elliptic cross sections. The CFD results demonstrated that the oil phase that passed through the elliptic MCs exceeding a threshold aspect ratio between 3 and 3.5 was cut off spontaneously into a small droplet with a diameter of approximately 40 microm. Sufficient space for water at the channel exit had to be maintained for successful droplet formation. The formation and shrinkage of a neck inside the channel caused an increased pressure difference inside the channel and an increased velocity value near the neck. The pressure and velocity values at the neck drastically changed, and the neck was cut off instantaneously just before the completion of droplet formation. This process was triggered by a gradually increased pressure difference between the circular neck and inflating oil phase. The findings obtained in this paper provide useful numerical and visual information about the droplet formation phenomena from the straight-through MCs. The CFD results were verified by the experimental results, showing that the CFD approach can help design a suitable channel structure.     

Application of 28Mg to the kinetic study of Mg uptake by rice plants

The time course of Mg uptake and release using intact rice plants and ²⁸Mg as a tracer is presented. Since there is no conventional Mg tracer available, ²⁸Mg was produced via ²⁷Al(α, 3p)²⁸Mg reaction using a cyclotron. Using the purified ²⁸Mg tracer, it was found that the uptake amount of ²⁸Mg by the rice plants increased linearly during 30 min of application. After ²⁸Mg treatment for 90 min, the roots were sequentially washed with iced solution for 120 min. Within about 10 min, almost all of the ²⁸Mg, that was thought to be weakly bound to the apoplast, was washed away.