Cellulose Synthesized by Acetobacter Xylinum in the Presence of Acetyl Glucomannan

Acetobacter xylinum was cultured in Hestrin-Schramm medium (control medium) and Hestrin-Schramm medium containing acetyl glucomannan (mannan medium). Loose bundles of the cellulose microfibrils are formed in the mannan medium in contrast to the normal ribbons being produced in the control medium. Rapid-freeze and substitution method followed by metal-shadowing revealed the droplet-like structures around the microfibril synthesized in the mannan medium. The cellulose synthesized in the mannan medium was stained heavily by the periodic acid-thiocarbohydrazide-silver proteinate (PATAg) method, while the cellulose synthesized in the control medium was not stained. X-ray diffractometry and FT-IR spectroscopy indicated that the addition of mannan induced a change in the crystal structure from the algal-bacterial type to the cotton-ramie type. Thus the presence of acetyl glucomannan in the medium prevents the assembly of cellulose microfibrils and changes the crystal structure of cellulose.     

Syntheses of fluorine-containing fused polycyclic compounds: photo-cycloaddition of indene to cyclic fluoro-olefins and some reactions concerning the adducts

Acetophenone photo-sensitized addition of indene to cyclic fluoro-olefins (1,2-dichlorohexafluorocyclopentene-1, 1,2-dichlorotetrafluorocyclobutene-1 and hexafluorocyclobutene) gave the corresponding cycloadducts in satisfactory yields. The cycloadducts obtained predominantly had exo configuration.Some reactions such as reduction, oxidation, dechlorination and halogenation, of the cycloadducts were also studied.     

Polymer-supported bases. IX. Synthesis and catalytic activity of polymer-bound 4-(1-pyrrolidino)pyridine moieties

Polystyrene-bound 4-(1-pyrrolidino)pyridine moieties were prepared by the reaction of chloromethylated polystyrene resins with pyrrolidinopyridine derivatives containing hydroxyl groups. The supported amines were effective catalysts for acylations of tert-alcohols or enols, acylrearrangements, and diester synthesis from epoxides and anhydrides. Some of the low ring-substituted (8–15%) catalysts exhibited high activity comparable to that of 4-(N,N-dimethylamino)pyridine, though the activity was a little lower than that of 4-(1-pyrrolidino)pyridine. The recovered catalysts can be re-used, except for acyl rearrangements, without significant decrease in activity.     

XPS studies on the chemical structure of the stabilized polyacrylonitrile fiber in the carbon fiber production process

In the carbon fiber production process from polyacrylonitrile (PAN), PAN precursor is heated first in air to secure stabilization in the succeeding carbonization process at higher temperature. The mechanism of the stabilization reaction and chemical structure of the stabilized PAN have been examined by x-ray photoelectron spectroscopy and elemental analysis. The stabilized PAN was determined to have a ladderlike structure consisting of 40% acridone ring, 30% naphtyridine ring, 20% hydronaphtyridine ring, and others. This structure well explains the stability of the polymer in the succeeding carbonization process on carbon fiber production with conjugated π-electron systems over the whole polymer chain and intermolecular hydrogen bonds. A comonomer addition to the precursor was found to accelerate the dehydrogenation reaction in the stabilization process.     

Structures and conformations of metabolites of antitumor cyclic hexapeptides, RA-VII and RA-X.

Metabolites of antitumor cyclic hexapeptides, RA-VII and -X which were isolated from Rubia cordifolia were studied by hepatic microsomal biotransformation in rats and in bile juice of rabbits to which these drugs were administered intravascularly. Their structures and conformations were elucidated by two-dimensional nuclear magnetic resonance techniques, temperature effect on NH protons and nuclear Overhauser effect experiments. Specific N-demethylation of Tyr-3, O-demethylation and hydroxylation at aromatic rings of Tyr-3 and -5 were observed. Compared with metabolites of RA-VII, most of RA-X was excreted unchanged in the bile juice. Relationship among their structures, conformations and antitumor activities is also discussed.     

Alstonia scholaris: Struktur des Indolalkaloides Narelin

Alstonia scholaris: The structure of the indole alkaloid nareline Besides the known akuammidine, picralinal, picrinine and pseudoakuammigine a new indole alkaloid called nareline (M=352) was isolated from Alstonia scholaris R. BR. , which belongs to the plant family of Apocynaceae. Its structure 2 was deduced by single crystal X-ray diffraction. 2 represents the absolute configuration. The spectroscopic data of 2 and its derivatives (Scheme 1) as well as their chemical behavior support this structure. In biogenetic sense nareline is related to the bases akuammiline ( 4 ) and picraline ( 5 ) (Scheme 2). In contrast to those the C-atom 5 is exocyclic and represents an aldehyde group which forms together with the oxygen atom of the N (4)-hydroxylamine group a cyclic half acetale. - By oxidation (CrO₃/CH₃COOH) of 2 the oxindol derivative 19 (oxonareline) is formed which contains a cyclic acetal as a partial structure element (Scheme 4).     

A novel synthesis of 2,3‐dihydro‐1H‐thieno[3,4‐b]pyrroles via ring transformation of cyclic sulfonium ylides by titanium(IV) chloride‐triethylamine system

A series of cyclic sulfonium ylides 4a‐h reacted with titanium( IV ) chloride in the presence of triethyl‐amine to give the corresponding fused 2,3‐dihydro‐1H‐thieno[3,4‐b]pyrroles 5a‐h , via a ring opening and recyclization. In contrast, treatment of compounds 4a, 4b, 4e and 4f with titanium(IV) chloride, triethy‐lamine and dimethylamine hydrochloride gave the corresponding thiophenes 6a, 6b, 6e and 6f . Furthermore, compounds 6a and 6b easily underwent cyclization with sodium hydride to afford the corresponding 5a and 5b .     

Hydrogen-bonded networks in organic conductors: crystal structures and electronic properties of charge-transfer salts of tetracyanoquinodimethane with 4,4'-biimidazolium having multiprotonated States

[structure: see text] Novel hydrogen-bonded charge-transfer salts of TCNQ with mono- and diprotonated 4,4'-biimidazolium were synthesized in order to demonstrate the high potential of the 4,4'-biimidazole system in a molecular conductor from the viewpoint of crystal engineering and electronic modulation. Crystal structure analyses of neutral 4,4'-biimidazole and TCNQ salts revealed the formation of two types of hydrogen-bonding modes of the 4,4'-biimidazole moiety depending on the protonated states. Neutral 4,4'-biimidazole possessed a linear chain mode of hydrogen-bonding to construct two-dimensional network. In the TCNQ salt of monoprotonated 4,4'-biimidazolium, the 4,4'-biimidazole moiety formed a dimer by a complementary mode of hydrogen-bonding. In contrast, the salt of diprotonated 4,4'-biimidazolium showed a double linear chain mode of hydrogen-bonding to construct a three-dimensional network. The formation of two types of hydrogen-bonding modes made the difference in the stacking patterns of TCNQ columns and in their transport properties. The TCNQ salt of diprotonated 4,4'-biimidazolium exhibited high electrical conductivity (sigma(rt) = 1.1 x 10(-1) S cm(-1)).     

Synthesis and two-electron redox behavior of diazuleno[2,1-a:1,2-c]naphthalenes

The Diels-Alder reaction of di-2-azulenylacetylene with tetraphenylcyclopentadienone afforded 7,8,9,10-tetraphenyldiazuleno[2,1-a:1,2-c]naphthalene in one pot via autoxidation of the presumed 1,2-di-2-azulenylbenzene derivative. In contrast, a similar reaction of bis(1-methoxycarbonyl-2-azulenyl)acetylene with tetraphenylcyclopentadienone gave the 1,2-di-2-azulenylbenzene derivative. The following cyclodehydrogenation reaction of the benzene derivative with iron(III) chloride afforded diazuleno[2,1-a:1,2-c]naphthalene 6,11-bismethoxycarbonyl derivative. The redox behavior of these novel diazuleno[2,1-a:1,2-c]naphthalenes was examined by cyclic voltammetry (CV). These compounds exhibited two-step oxidation waves at +0.22 to +0.71 V upon CV, which revealed the formation of a radical cation and dication stabilized by the fused two azulene rings under the electrochemical oxidation conditions. Since the 1,2-di-2-azulenylbenzene derivative was oxidized at higher oxidation potentials (+0.83 and +1.86 V), the fusion of the two azulene rings to naphthalene increased electron-donating properties because of the formation of a closed-shell dicationic structure. Formation of the radical cation was characterized by UV-vis spectroscopy under the electrochemical oxidation conditions, although no evidence was obtained for the presumed dication under the conditions of the UV-vis spectroscopy measurement.     

The first example of the stereoselective synthesis of 7 beta-carbamoyl-4,5alpha-epoxymorphinan via a novel and reactive gamma-lactone

7beta-Carbamoyl-4,5alpha-epoxymorphinans 5 were stereoselectively synthesized from the 7alpha-carboxylate intermediate 3 in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and amines under reflux conditions in mesitylene via a novel and reactive gamma-lactone 7. These were the first examples of the stereoselective syntheses of 7beta-substituted 4,5alpha-epoxymorphinans. The mechanism of the reaction process was elucidated as follows: 1) epimerization of 7alpha-carboxylate 3, 2) intramolecular lactonization of 7beta-carboxylate 6, and 3) aminolysis of the resultant gamma-lactone 7. The aminolysis of the isolated reactive gamma-lactone 7 with allylamine and the alcoholysis with MeOH in the presence of NaBH(4) proceeded at room temperature. The gamma-lactone 7 can be a useful intermediate for the preparation of 7beta-substituted 4,5alpha-epoxymorphinans that would be potent selective delta opioid receptor ligands. The stereoselective syntheses of the 7alpha-carbamoyl-4,5alpha-epoxymorphinans 9 from 7alpha-carboxylate 3 via 7alpha-carboxylic acid were also successful.