Synthesis of SET–LRP‐induced galactoglucomannan‐diblock copolymers

Polysaccharides are biorenewable and biodegradable starting materials for the development of functional materials. The synthesis of a monofunctional macroinitiator for single electron transfer‐living radical polymerization was successfully developed from a wood polysaccharide‐O‐acetyl galactoglucomannan (GGM) using a beforehand synthesized amino‐functional α‐bromoisobutyryl derivative applying reductive amination. The GGM macroinitiator was employed to initiate a controlled radical polymerization of [2‐(methacryloyloxy)ethyl]trimethylammonium chloride (MeDMA), methyl methacrylate (MMA), and N‐isopropylacrylamide (NIPAM) using Cu⁰/Me₆‐Tren as a catalyst. The either charged or amphiphilic GGM‐b‐copolymers with different chain lengths of the synthetic block were successfully synthesized without prior hydrophobization of the GGM chain and dimethyl sulfoxide (DMSO) or DMSO/water mixtures were used as solvents. This novel synthetic approach may find untapped potentials particularly for the development of polysaccharide‐based amphiphilic additives for cosmetics or paints and for the design of novel temperature or pH responsive polymers with such potential applications as in drug delivery systems or in biocomposites. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5100–5110     

Side Products in Nucleotide Chemistry

Abstract

Alkyl bisaminophosphorodiamidites¹ (1) has been shown to be versatile reagents for in situ preparation of d-nucleoside-3-phosphoramidites^2,3,4 (2.)     

Oligodeoxynucleotide analogues containing 3′-deoxy-3′-C-threo-hydroxymethylthymidine: Synthesis, hybridization properties and enzymatic stability

Novel Oligodeoxynucleotide analogues containing 3′-C-threo-methylene phosphodiester internucleoside linkages were synthesized on automated DNA-synthesizers using the phosphoramidite approach. The sugar modified phosphoramidite building block 5 was obtained by phosphitylation of 1-(2,3-dideoxy-5-O-(4,4′-dimethoxytrityl)-3-C-hydroxymethyl-β-D-threo-pentofuranosyl)thymine (4) which was synthesized in only three steps from 5′-O-(4,4′-dimethoxytrityl)thymidine (1). The hybridization properties and enzymatic stability of the oligonucleotide analogues were studied by UV experiments. 17-Mers having one or three modifications in the middle or two modifications in each end hybridized to DNA with moderate lowered affinity compared to unmodified 17-mers (ΔT_m 1–3°C per modification). Furthermore, the end-modified and all-modified oligonucleotides were stable towards snake venom phosphodiesterase.     

Composition and properties of freeze-dried products of nicotinic acid withβ-cyclodextrin and heptakis (2,6-0-dimethyl)-β-cyclodextrin

The purpose of the study was to examine the formation of inclusion compounds in the freeze-dried products obtained from aqueous solutions of nicotinic acid and -cyclodextrin (-CD), or heptakis (2,6-0-dimethyl)--cyclodextrin (DIMEB). The molar ratios used were 1:1 and 2:1. In addition two freezing temperatures (–40 and –196°C) and different secondary drying temperatures (+50 and +80°C) were used. Freeze-dried products with -CD obtained after low temperature freezing are of the same crystallographic structure as seen in a pure inclusion compound prepared by coprecipitation. Amorphous products were formed after fast freezing. The molar ratios of included nicotinic acid in the freeze-dried products vary — dependent on the preparation conditions — between 0.75:1 and 1:1. A factorial design proves that the included drug amount can be increased by enhancement of the amount of nicotinic acid used, by faster freezing, and by the combination of these two factors. The proof of inclusion formation was given by a combination of X-ray diffractography, differential scanning calorimetry, thermogravimetry and thermofractography.The freeze-dried preparations obtained with DIMEB were amorphous mixtures of the two components. No proof for inclusion of the nicotinic acid in the cyclodextrin cavity could be given. Higher (–40°C) or lower (–196°C) freezing temperatures and the running of the secondary drying process could not influence these results. The very low stability constant of the complex and steric reasons are responsible for this behavior.     

Quantum field theoretical methods in chemically bonded systems II

Summary Many-body perturbation theory is derived for chemical bonds. Paired quasiparticles represent the bonds. Products of the paired quasiparticles define a model Bardeen-Cooper-Schrieffer function. The pairing force is added as a model interaction to the self-consistent problem. The starting model is based on valency and adiabatic symmetry correlation. Symmetries are enforced by the model Hamiltonian. Perturbative corrections are expressed as ordinary Feynman diagrams. The number of diagrams needed is the same as for particle-hole theory.This work was supported in part by the U.S. Department of the Navy, Space and Naval Warfare Systems Command under Contract N00039-89-C-0001, and in part by NATO Research Grant 1861. It was presented, in part, at the A.C. Wahl Memorial Session, Molecular Spectroscopy Symposium, Columbus, Ohio, 1984; and Midwest Theoretical Chemistry Conference, Milwaukee, Wisconsin, 1985.     

Electron distribution on an intramolecular hydrogen bond: A semiempirical AM1 study

Dipole moments of seven molecules were studied by AM1, each containing an intramolecular hydrogen bond between a hydroxyl group and a carbonyl or nitro group as hydrogen acceptors. The hydrogen bond causes two electron shifts: from H to O within the hydroxyl group and from C to O within the carbonyl group. The latter is accompanied by withdrawal of electrons from even more distant atoms. If the total electron density change is expressed as a vector, its direction is close to the direction of the O-H bond. This electron redistribution is in agreement with the previous, somewhat, puzzling experimental results. However, it differs from the commonly accepted picture according to which electron density changes on the hydrogen acceptor moiety are less important than those on the O-H bond.Dedicated to Professor Viktor Gutmann on the occasion of his 70th birthday.     

New Dolabellane Derivatives from the Brown Alga Dictyota pardalis

Reinvestigation of the brown alga Dictyota pardalis f. pseudohamata CRIBB led to the crystallization of 1 and to the isolation of the two new dolabellane derivatives 2 and 3 . X-Ray analysis of 1 and 2 , together with detailed 1D-and 2D-NMR studies on 2 and 3 , allowed their structures to be elucidated as (1R*,3S*,7S*,11R*,4Z)-dolabella-4,8(17), 12(18)-triene-3,7-diol ( 1 ), (1R*,3S*,4S*,7S*,8S*,11R*,14R*,12E)-3,4:7,8-diepoxydolabe11-12-ene-14, 18-diol ( 2 ), and (1R*,3S*,4S*,7S*,8S*,11R*,14R*)-3,4:7,8-diepoxy-l,4,8,12,12-pentamethylbicyclo[9. 3. 0]tetra-decan-14-ol( 3 ).