Base-catalyzed Degradations of Carbohydrates. III. Formation of a Novel Perester from 1-O-Acetyl-3-deoxy-2,4,6-tri-O-methyl-α-D-erytho-hex-2-enopyranose

1973 ◽  
Vol 51 (3) ◽  
pp. 388-393 ◽  
Author(s):  
G. O. Aspinall ◽  
R. R. King ◽  
Zofia Pawlak
Keyword(s):  
Acetic Anhydride ◽  
Spectral Data ◽  
Trifluoroacetic Acid ◽  
Oxidative Degradation ◽  
Chemical Degradation ◽  
Reductive Decomposition

1-O-Acetyl-3-deoxy-2,4,6-tri-O-methyl-α-D-erythro-hex-2-enopyranose (1) reacts with m-chloroperbenzoic acid to give a novel perester, which has been assigned the structure 1,2-O-(1′-m-chloroperbenzoyl-oxyethylidene)-2-methoxy-4,6-di-O-methyl-α-D-glucopyranose (2), on the basis of spectral data and chemical degradation. The perester 2 and the derived acetate 3 undergo oxidative degradation on treatment with trifluoroacetic acid to give 3,5-di-O-methyl- (4) and 2-O-acetyl-3,5-di-O-methyl-D-arabinonolactone (5), respectively. Reductive decomposition of the acetylated perester 3 yields 1,3-di-O-acetyl-4,6-di-O-methyl-α-D-arabino-hexopyranosulose (6), which, on treatment with acetic anhydride in pyridine, gives successively 1,2,3-tri-O-acetyl-4,6-di-O-methyl-α-D-erythro-hex-2-enopyranose (7), 2-O-acetyl-1-deoxy-4,6-di-O-methyl-α-D-erythro-hex-1-enopyranose-3-ulose (8), and 5-acetoxy-2-(methoxy-methyl)-4H-pyran-4-one (9).

Clionamide, a major metabolite of the sponge Clionacelata Grant

1979 ◽  
Vol 57 (17) ◽  
pp. 2325-2328 ◽  
Author(s):  
Raymond J. Andersen ◽  
Richard J. Stonard
Keyword(s):  
Spectral Analysis ◽  
Spectral Data ◽  
Major Metabolite ◽  
Chemical Degradation ◽  
Hydrogenation Product ◽  
Cliona Celata

Clionamide, the major metabolite of the burrowing sponge Cliona celata, has been isolated. The structure of clionamide (1) was shown to be (2S)-N-((1E)-5,6,7-trihydroxystyr-1-yl)-2-amino-3-(6-bromoindol-3-yl)propionamide by spectral analysis and by interconversion to its tetracetyl derivative 2. The structure of 2 was determined from spectral data and extensive chemical degradation and was confirmed by the synthesis of its ultimate hydrogenation product, N-(5,6,7-triacetoxypheneth-1-yl)-2-acetamido-3-(indol-3-yl)propionamide (11).

Degradation resistance of silicon carbide diesel particulate filters to diesel fuel ash deposits

2004 ◽  
Vol 19 (10) ◽  
pp. 2913-2921 ◽  
Author(s):  
D. O’Sullivan ◽  
M.J. Pomeroy ◽  
S. Hampshire ◽  
M.J. Murtagh
Keyword(s):  
Silicon Carbide ◽  
Construction Material ◽  
Oxidative Degradation ◽  
Lubricant Additive ◽  
Chemical Degradation ◽  
Particulate Filter ◽  
Diesel Particulate ◽  
Diesel Particulate Filters ◽  
Particulate Filters ◽  
Series Of Experiments

A series of experiments were conducted to investigate chemical interactions between silicon carbide (SiC) and synthetic ash compositions expected to be deposited on the surfaces and within the pore structure of a diesel particulate filter. The chosen ash compositions simulated those arising from lubricants and three fuel types: standard diesel, diesel containing ferrocene as a catalytic additive, and diesel containing a cerium-based catalyst. Results demonstrated that SiC suffered little chemical or oxidative degradation in the presence of the ashes at 900 °C. For the ash not containing Fe or Ce, ash sintering effects were a possible mechanism causing filter blockage at temperatures above 970 °C. For ashes containing Fe or Ce, appreciable sintering effects were not observed below 1100 °C. Based upon the work conducted the suitability of SiC as a construction material for diesel particulate filters is not compromised by chemical degradation in the presence of lubricant/additive derived ash at temperatures less than 1100 °C.

Tetracyclic triterpenes. VIII. The skeletal rearrangement of 3β-acetoxy-9α,11α-epoxy-5α-lanostan-7-one: 13- and 10-methyl group migration

1985 ◽  
Vol 63 (6) ◽  
pp. 1280-1286 ◽  
Author(s):  
Zdzisław Paryzek ◽  
Roman Wydra
Keyword(s):  
Acetic Anhydride ◽  
Spectral Data ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
Major Product ◽  
Chemical Transformations ◽  
Skeletal Rearrangement ◽  
Methyl Group ◽  
Group Migration

The boron trifluoride etherate catalyzed rearrangement of 3β-acetoxy-9α, 11α-epoxy-5α-lanostan-7-one (1) in acetic anhydride resulted in formation of 19(10 → 9β)abeo compounds 2 and 4 along with 18(13 → 12β)abeo compound 5, as the major product. These structures are supported by spectral data and chemical transformations. The possible mechanism of the rearrangement is discussed.

Analysis of lignin and extractives in the oak wood of the 17th century warship Vasa

Holzforschung ◽  
2014 ◽  
Vol 68 (4) ◽  
pp. 419-425 ◽  
Author(s):  
Dina Dedic ◽  
Teresia Sandberg ◽  
Tommy Iversen ◽  
Tomas Larsson ◽  
Monica Ek
Keyword(s):  
Oxidative Degradation ◽  
Magic Angle Spinning ◽  
Chemical Degradation ◽  
Gas Chromatography Mass Spectrometry ◽  
Magic Angle ◽  
Chemical Mechanisms ◽  
Wood Extracts ◽  
Cellulose Depolymerization ◽  
Angle Spinning ◽  
C Nmr

Abstract The wood in the 17th century Swedish warship Vasa is weak. A depolymerization of the wood’s cellulose has been linked to the weakening, but the chemical mechanisms are yet unclear. The objective of this study was to analyze the lignin and tannin moieties of the wood to clarify whether the depolymerization of cellulose via ongoing oxidative mechanisms is indeed the main reason for weakening the wood in the Vasa. Lignin was analyzed by solid-state nuclear magnetic resonance [cross-polarization/magic-angle spinning (CP/MAS) 13C NMR] and by means of wet chemical degradation (thioacidolysis) followed by gas chromatography-mass spectrometry (GC-MS) of the products. No differences could be observed between the Vasa samples and the reference samples that could have been ascribed to extensive lignin degradation. Wood extracts (tannins) were analyzed by matrix-assisted laser desorption ionization (MALDI) combined with time-of-flight (TOF) MS and 13C NMR spectroscopy. The wood of the Vasa contained no discernible amounts of tannins, whereas still-waterlogged Vasa wood contained ellagic acid and traces of castalagin/vescalagin and grandinin. The results indicate that the condition of lignin in the Vasa wood is similar to fresh oak and that potentially harmful tannins are not present in high amounts. Thus, oxidative degradation mechanisms are not supported as a primary route to cellulose depolymerization.

Analysis of acids and degradation products related to iron and sulfur in the Swedish warship Vasa

Holzforschung ◽  
2008 ◽  
Vol 62 (6) ◽  
Author(s):  
Gunnar Almkvist ◽  
Ingmar Persson
Keyword(s):  
Formic Acid ◽  
Degradation Products ◽  
Oxidative Degradation ◽  
Sulfur Oxidation ◽  
Surface Region ◽  
Sulfur Compounds ◽  
Chemical Degradation ◽  
Conservation Treatment ◽  
Organic Sulfur Compounds ◽  
Maldi Tof

Abstract Aqueous wood extracts from the historic Swedish warship Vasa have been analyzed by 1H-NMR spectroscopy, ion chromatography, and matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry as part of studies on the chemical degradation related to increased levels of iron and sulfur. The results show that low molecular organic acids have accumulated in the Vasa wood after the 1961 salvage. The increased acidity was found in a context of chemical degradation of the wood polymers and the conservation agent polyethylene glycol (PEG) in iron-rich parts of the timber. Formic, glycolic and oxalic acid are all possible end-products of oxidative degradation of wood polymers, whereas hydrolysis of acetyl groups in xylan may have contributed to increased concentrations of acetic acid. MALDI-TOF spectra of PEG displaced towards low-molecular PEG oligomers, as reported earlier, were accompanied by increased levels of formic acid, indicating oxidative degradation of PEG. PEG with a carboxylic acid end group (PEGC) was observed to a minor degree in the wood. However, analysis of stored conservation treatment solutions showed high concentrations of PEGC yielding significant contributions to the acidity during the 1960s conservation period. PEGC was probably formed as a result of microbial processes during the early conservation regime. Calculations using concentrations and well-established acidity constants show that oxalic and formic acid are the primary contributors to a low pH in the wood. The increased acidity in the interior of the wood was found in the absence of sulfur compounds but in a context of iron. The majority of the sub-samples with significant levels of sulfate in the surface region with a prospective sulfur oxidation, however, showed neither a decreased pH nor significant depolymerization. This indicates that oxidation pathways of organically bound sulfur do not necessarily produce strong acids, and thereby free protons, as the final product. These observations imply opposing effects of iron and reduced sulfur species, with iron acting as a initiator in oxidative reactions of Fenton type, whereas the reduced organic sulfur compounds may act as anti-oxidants.

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