Mass Spectra of Spirobenzylisoquinoline Alkaloids

1971 ◽  
Vol 49 (18) ◽  
pp. 3025-3037 ◽  
Author(s):  
C. K. Yu ◽  
D. B. MacLean
Keyword(s):  
Carbonyl Group ◽  
Mass Spectra ◽  
Major Ions ◽  
Membered Ring ◽  
Hydroxyl Group ◽  
Model Compounds ◽  
Fragmentation Mechanisms

The mass spectra of a number of spirobenzylisoquinoline alkaloids, several of their derivatives, and some model compounds are recorded and discussed. Fragmentation mechanisms are proposed for the formation of the major ions in the spectra of compounds containing one and two oxygen functions in the five-membered ring. The spectra of compounds containing a carbonyl group differ markedly from those having a hydroxyl group in the five-membered ring. Several model compounds were synthesized and characterized and their spectra compared with those of the alkaloids.

A New Approach Towards the Yellowing Inhibition of Mechanical Pulps. Part I: Selective Removal of α-Hydroxyl and α-Carbonyl Groups in Lignin Model Compounds

Holzforschung ◽  
1999 ◽  
Vol 53 (1) ◽  
pp. 43-48 ◽  
Author(s):  
T. Q. Hu ◽  
G. Leary ◽  
D. Wong
Keyword(s):  
Carbonyl Group ◽  
Trifluoroacetic Acid ◽  
Selective Removal ◽  
Hydroxyl Group ◽  
Carbonyl Groups ◽  
Model Compounds ◽  
Ether Linkage ◽  
Lignin Model Compounds ◽  
Lignin Model ◽  
Mechanical Pulps

Summary The α-hydroxyl group in lignin model compounds 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol (1) and 1-(4-hydroxy-3-methoxyphenyl)ethanol (3), and the α-carbonyl group in 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)ethan-1-one (5) are removed by treatment of the model compounds with trifluoroacetic acid (CF3CO OH) and triethylsilane (Et3sih) in methylene chloride. The reaction is highly chemoselective and it tolerates the lignin γ-hydroxyl group, phenol and β-O-4-aryl ether linkage. The α-hydroxyl group in 1 has also been removed with triethylsilane in aqueous trifluoroacetic acid (CF3CO OH : H2o = 75 : 25). The combination of trifluoroacetic acid and sodium borohydride, or sodium triacetoxyborohydride, is also effective in removing the α-carbonyl group in 5 and the α-hydroxyl group in lignin model compound 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)ethanol (7) and in milled wood lignin. The selective removal of the lignin α-hydroxyl and α-carbonyl groups may potentially be used, in conjunction with the protection of the lignin phenol, to inhibit the light and/or heat-induced yellowing of mechanical pulps.

Structure Revision of Protoaculeine B, a Posttranslationally Modified N-Terminal Residue in the Peptide Toxin Aculeine B

2020 ◽  
Author(s):  
Raku Irie ◽  
Kei Miyako ◽  
Satoko Matsunaga ◽  
Ryuichi Sakai ◽  
Masato Oikawa
Keyword(s):  
Mass Spectra ◽  
Chemical Reactivity ◽  
Model Compounds ◽  
Structural Revision ◽  
Structure Revision ◽  
Peptide Toxin ◽  
One Step ◽  
Marine Peptide ◽  
Synthetic Models ◽  
Long Chain

<div>Here, we newly propose the structure of protoaculeine B, an N-terminal moiety of the marine peptide toxin aculeine B, as possessing the cis-disubstituted tetrahydro-beta-carboline framework. We prepared two truncated model compounds that lack long-chain polyamine by one-step Pictet-Spengler reaction of tryptophan, and compared the NMR and mass spectra and chemical reactivity with those of natural protoaculeine B. The synthetic models reproduced the profiles of the natural product well, which was conclusive for the structural revision.</div>

Inductive effect in EI-mass spectra of some 5,6-dihalogenides and 5,6-halohydrins of 5α-cholestan-3β-ol and 3β-acetoxy-5α-cholestane

1982 ◽  
Vol 47 (11) ◽  
pp. 2946-2960 ◽  
Author(s):  
Antonín Trka ◽  
Alexander Kasal
Keyword(s):  
Mass Spectra ◽  
Inductive Effect ◽  
Molecular Ions ◽  
Hydroxyl Group ◽  
Halogen Atoms ◽  
Derivatives Of

Partial EI-mass spectra of 3β-hydroxy- and 3β-acetoxy-5α-cholestanes substituted in positions 5α-, 6β- or 5α,6β- with a hydroxyl group or halogen atoms (fluorine, chlorine, bromine) are presented. The molecular ions of 5α,6β-disubstituted derivatives of 3β-hydroxy-5α-cholestane (or of its 3-acetate) are considerably more stable than the corresponding monosubstituted derivatives if at least one of the pair of the vicinal substituents is chlorine or fluorine. This increase in stability, most striking in 5α- and 6β-fluoro compounds, is explained by the inductive effect.

A new non-azole inhibitor of ABA 8′-hydroxylase: Effect of the hydroxyl group substituted for geminal methyl groups in the six-membered ring

2006 ◽  
Vol 16 (12) ◽  
pp. 3302-3305 ◽  
Author(s):  
Yoshiharu Araki ◽  
Arisa Miyawaki ◽  
Tomoyuki Miyashita ◽  
Masaharu Mizutani ◽  
Nobuhiro Hirai ◽  
...  
Keyword(s):  
Membered Ring ◽  
Hydroxyl Group ◽  
Methyl Groups

ChemInform Abstract: 3a-Azaazulenones Containing a Carbonyl Group in the 5-Membered Ring.

ChemInform ◽  
1988 ◽  
Vol 19 (9) ◽  
Author(s):  
W. FLITSCH ◽  
R. A. JONES ◽  
M. HOHENHORST
Keyword(s):  
Carbonyl Group ◽  
Membered Ring

scholarly journals Study of the Reactivity of Lignin Model Compounds to Fluorobenzylation Using 13C and 19F NMR: Application to Lignin Phenolic Hydroxyl Group Quantification by 19F NMR

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3211
Author(s):  
Esakkiammal Sudha Esakkimuthu ◽  
Nathalie Marlin ◽  
Marie-Christine Brochier-Salon ◽  
Gérard Mortha
Keyword(s):  
Reaction Medium ◽  
19F Nmr ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Nmr Analysis ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Wide Range ◽  
Lignin Model ◽  
13C And 19F Nmr

Lignin is an aromatic biopolymer derived from lignocellulosic biomass. Providing a comprehensive structural analysis of lignin is the primary motivation for the quantification of various functional groups, with a view to valorizing lignin in a wide range of applications. This study investigated the lignin fluorobenzylation reaction and performed a subsequent 19F-NMR analysis to quantify hydroxyl groups, based on a work developed two decades ago by Barrelle et al. The objectives were to check the assignments proposed in this previous study and to examine the reactivity of various types of lignin hydroxyls with the derivatization agent. Selected lignin model compounds containing phenolic and aliphatic hydroxyls were subjected to the fluorobenzylation reaction, and the obtained reaction medium was analyzed by 13C and 19F NMR spectroscopy. The model compound results showed that phenolic hydroxyls were totally derivatized, whereas aliphatic hydroxyls underwent minimal conversion. They also confirmed that 19F NMR chemical shifts from −115 ppm to −117.3 ppm corresponded to phenolic groups. Then, a 19F NMR analysis was successfully applied to Organosolv commercial lignin after fluorobenzylation in order to quantify its phenolic group content; the values were found to be in the range of the reported values using other analytical techniques after lignin acetylation.

Diazabenzenes. I. Synthesis of some t-butylpyrazines and their N-oxides

1972 ◽  
Vol 25 (12) ◽  
pp. 2671 ◽  
Author(s):  
RF Evans ◽  
KN Mewett
Keyword(s):  
Steric Hindrance ◽  
Mass Spectra ◽  
Ammonium Acetate ◽  
Spectroscopic Properties ◽  
Iron Pentacarbonyl ◽  
Membered Ring ◽  
Low Resolution ◽  
Butyl Lithium ◽  
Pyrazine Ring ◽  
Resolution Mass

Steric hindrance prevented formation of tetra-t-butylpyrazine either when pivaloin was heated with ammonium acetate or when pivalil monooxime was reduced with zinc and alkali. Diminution of the steric hindrance of the t-butyl groups by masking them by incorporation into a seven-membered ring containing sulphur was of no avail. 2,5-Di-t- butylpyrazine resulted from the analogous reduction of t-butyl-glyoxal dioxime and could be converted into its N-oxide and N,N?-dioxide. t- Butyl-lithium reacted with the pyrazine and the mono-N-oxide to give a mixture of products including 2,3,5-tri-t-butylpyrazine whose spectroscopic properties suggested a buckling of the pyrazine ring. Benzonitrile and diphenylacetylene reacted independently in the presence of iron pentacarbonyl and gave, inter alia, 2,4,6-triphenyl- 1,3,5-triazine and hexaphenylbenzene respectively. ��� The most prominent features of the low resolution mass spectra of these pyrazines and some of their precursors are discussed and rationalized.

Synthese von vier- und achtgliedrigen Heterocyclen, die Schwefel, Stickstoff und Phosphor enthalten, und die Röntgenstrukturanalyse eines phosphorhaltigen achtgliedrigen SN-Ringes / Synthesis of Four- and Eight-Membered Heterocycles Containing Sulfur, Nitrogen and Phosphorus and the X-ray Structure of a Phosphorus-Containing Eight-Membered SN-Ring

1980 ◽  
Vol 35 (9) ◽  
pp. 1130-1136 ◽  
Author(s):  
Herbert W. Roesky ◽  
Sushil K. Mehrotra ◽  
Christoph Platte ◽  
Djamrnschid Amirzadeh-Asl ◽  
Bernhard Roth
Keyword(s):  
Tertiary Amine ◽  
Phosphorus Atom ◽  
Mass Spectra ◽  
Phosphorus Pentachloride ◽  
Membered Ring ◽  
Phosphonium Salts ◽  
Nitrogen And Phosphorus ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Phosphorus Containing

Eight-membered rings of the composition [SO2(NR)2PR′]2 3a-d with R = CH3, C2H5, and R′ = CH3, C6H5, were prepared from substituted sulfamides and dichlorophosphanes in the presence of a tertiary amine. These molecules were characterized on the basis of 1H and 31P NMR investigations and of mass spectra. 3 a reacts with phosphorus pentachloride to yield the spirocyclic derivative 4 with the phosphorus atom in the center of two four-membered rings. Methyliodide reacts with 3 a and 3 b under opening of the eight- membered ring and formation of phosphonium salts. The structure of 3 b is discussed in detail. 8b crystallizes in the orthorhombic space group Pna 21 with a = 12.60(0), b = 13.27(1), c = 12.62(4) Å.

Untersuchungen zur Ringkontraktion am 1,4-Dithia-2,6-diaza-3,5-diborinan-System/ Studies on Ring Contraction of the l,4-Dithia-2,6-diaza-3,5-diborinane System

1988 ◽  
Vol 43 (8) ◽  
pp. 959-962 ◽  
Author(s):  
Carl Habben ◽  
Anton Meiler ◽  
Stefan Pusch
Keyword(s):  
Mass Spectra ◽  
Ring System ◽  
Membered Ring ◽  
Ring Contraction ◽  
C Nmr

AbstractThe 1,4-dithia-2,6-diaza-3,5-diborinanes 1a-d react with elemental sodium with formation of the 1,3-diaza-2,4-diboretidines 2a-d. By use of more sodium in case of 1 d or 3,5-bis(diethylamino)- 2-cyclohexyl-6-trimethylsilyldiborinane, the 1,3-thiaza-2,4-diboretidines 3 were formed. 3.5-Dimethyl-2,6-bis(trimethylsilyl)-1,4-dithia-2,6-diaza-3,5-diborinane gives the borazine 4, The reaction of di-t-butyl-sulfurdiimide with 2,6-di-t-butyl-3,5-dimethyl-1,4-dithia-2,6-diaza-3,5-diborinane leads by ring contraction to the four-membered ring system 5. 1H, 11B, 13C NMR and mass spectra are reported and discussed.

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