NMR Studies of 2-Aryl Derivatives of Benzimidazole, Benzimidazolium Ion, and Benzimidazoline

Heterocycles ◽  
2009 ◽  
Vol 78 (2) ◽  
pp. 425 ◽  
Author(s):  
In-Sook Han Lee ◽  
Chang Kiu Lee
Keyword(s):  
Nmr Studies ◽  
Derivatives Of

1,3-dipolar cycloaddition in the synthesis of glycoconjugates of natural chlorins and bacteriochlorins

2009 ◽  
Vol 13 (03) ◽  
pp. 336-345 ◽  
Author(s):  
Mikhail A. Grin ◽  
Ivan S. Lonin ◽  
Anna A. Lakhina ◽  
Elena S. Ol'shanskaya ◽  
Alexey I. Makarov ◽  
...  
Keyword(s):  
Triple Bond ◽  
Tautomeric Form ◽  
Click Reaction ◽  
Copper Cation ◽  
Water Soluble ◽  
Dipolar Cycloaddition ◽  
Nmr Studies ◽  
Metal Free ◽  
Cu Complex ◽  
Derivatives Of

Glucose-, galactose- and lactose-containing photosensitizers based on derivatives of chlorophyll a and bacteriochlorophyll a were synthesized with the use of [3+2] cycloaddition between sugar azides and triple bond derivatives of chlorins and bacteriochlorins. Unlike bacteriochlorin cycloimide, chlorin was detected to form a Cu -complex during the click reaction. An approach to the synthesis of metal-free glycosylated chlorins was developed with the use of "protection" by Zn 2+ cation and subsequent demetalation. It is based on the action of alkynyl chlorin e6 derivative Zn -complex, which is resistant to the substitution by copper cation. Bacteriochlorin p cycloimide conjugate with per-acetylated β-D-lactose was obtained and shown to become water-soluble after unblocking of the lactose hydroxy functions. NMR studies allowed for the elucidation of structure, tautomeric form and conformation of the obtained compounds.

The syntheses of 6-C-alkyl derivatives of methyl α-isomaltoside for a study of the mechanism of hydrolysis by amyloglucosidase

2001 ◽  
Vol 79 (2) ◽  
pp. 238-255 ◽  
Author(s):  
Ulrike Spohr ◽  
Nghia Le ◽  
Chang-Chun Ling ◽  
Raymond U Lemieux
Keyword(s):  
Hydrogen Bonds ◽  
Molecular Model ◽  
Aromatic Amino Acids ◽  
Hydroxyl Group ◽  
Bulk Solution ◽  
Anomeric Effect ◽  
Nmr Studies ◽  
Intermolecular Hydrogen Bonds ◽  
Model Calculations ◽  
Derivatives Of

The epimeric (6aR)- and (6aS)-C-alkyl (methyl, ethyl and isopropyl) derivatives of methyl α-isomaltoside (1) were synthesized in order to examine the effects of introducing alkyl groups of increasing bulk on the rate of catalysis for the hydrolysis of the interunit α-glycosidic bond by the enzyme amyloglucosidase, EC 3.2.1.3, commonly termed glucoamylase (AMG). It was previously established that methyl (6aR)-C-methyl α-isomaltoside is hydrolysed about 2 times faster than methyl α-isomaltoside and about 8 times faster than its S-isomer. The kinetics for the hydrolyses of the ethyl and isopropyl analogs were also recently published. As was expected from molecular model calculations, all the R-epimers are good substrates. A rationale is presented for the catalysis based on conventional mechanistic theories that includes the assistance for the decomposition of the activated complex to products by the presence of a hydrogen bond, which connects the 4a-hydroxyl group to the tryptophane and arginine units. It is proposed that activation of the initially formed complex to the transition state is assisted by the energy released as a result of both of the displacement of perturbed water molecules of hydration at the surfaces of both the polyamphiphilic substrate and the combining site and the establishment of intermolecular hydrogen bonds, i.e., micro-thermodynamics. The dissipation of the heat to the bulk solution is impeded by a shell of aromatic amino acids that surround the combining site. Such shields are known to be located around the combining sites of lectins and carbohydrate specific antibodies and are considered necessary to prevent the disruption of the intermolecular hydrogen bonds, which are of key importance for the stability of the complex. These features together with the exquisite stereoelectronic dispositions of the reacting molecules within the combining site offer a rationalization for the catalysis at ambient temperatures and near neutral pH. The syntheses involved the addition of alkyl Grignard reagents to methyl 6-aldehydo-α-D-glucopyranoside. The addition favoured formation of the S-epimers by over 90%. Useful amounts of the active R-isomers were obtained by epimerization of the chiral centers using conventional methods. Glycosylation of the resulting alcohols under conditions for bromide-ion catalysis, provided methyl (6aS)- and (6aR)-C-alkyl-hepta-O-benzyl-α-isomaltosides. Catalytic hydrogenolysis of the benzyl groups afforded the desired disaccharides. 1H NMR studies established the absolute configurations and provided evidence for conformational preferences.Key words: amyloglucosidase (AMG), exo-anomeric effect, 6-C-alkyl-α-D-glucopyranosides and isomaltosides, mechanism of enzyme catalysis.

scholarly journals Synthesis and NMR Studies of Z- and E-Isomers of 10-Oxo and 10-Hydroxy Derivatives of Amitriptyline and Nortriptyline.

1983 ◽  
Vol 37b ◽  
pp. 335-340 ◽  
Author(s):  
Niels Lassen ◽  
Jens Perregaard ◽  
Toshiaki Nishida ◽  
Curt R. Enzell ◽  
Jan-Eric Berg ◽  
...  
Keyword(s):  
Nmr Studies ◽  
Derivatives Of

Diyne Cyclization in Camphor Derivatives - Experimental and Theoretical Investigation

1996 ◽  
Vol 51 (11) ◽  
pp. 1655-1662 ◽  
Author(s):  
Gabriele Wagner ◽  
Christian Heiß ◽  
Uwe Verfiirth ◽  
Rudolf Herrmann
Keyword(s):  
Oxygen Atom ◽  
Theoretical Investigation ◽  
Positive Charge ◽  
Membered Ring ◽  
Titanium Chloride ◽  
Nmr Studies ◽  
Methylene Carbon ◽  
Camphor Derivatives ◽  
Exocyclic Methylene ◽  
Derivatives Of

Derivatives of 3-oxo-camphorsulfonimide (1) with two phenylethynyl groups in the endo positions at the carbons C-2 and C-3 were prepared, and their reactivity towards halogenes and titanium chloride was studied. In every case, the two ethynyl groups led to the annulation of a five-membered ring to the bicyclo[2 .2 .1] system in an orientation which depends on the bulkiness of the additional substituent in position 3. NMR studies show that cationic species like 6 and 8 are the first detectable intermediates. They not only contain the fused five-membered ring but also a bond between its exocyclic methylene carbon and an oxygen atom of the sulfonyl group, thus transferring the positive charge mainly to sulfur. Semiempirical calculations (PM3) suggest two intermediates in the formation of such cations.

Preparation and Spectroscopic Characterisation of a Series of Heterobimetallic N-phenyldiethanolaminate-alkoxide Derivatives of Oxovanadium(V)

2005 ◽  
Vol 2005 (6) ◽  
pp. 352-355 ◽  
Author(s):  
Rajendra Singh Ghadwal ◽  
Ram C. Mehrotra ◽  
Anirudh Singh
Keyword(s):  
Molecular Weight ◽  
Spectral Studies ◽  
Metal Alkoxides ◽  
Nmr Studies ◽  
Mass Spectral ◽  
Elemental Analyses ◽  
Derivatives Of ◽  
Spectroscopic Characterisation

Reaction of VO(OPri)3 with two equivalents of N-phenyldiethanolamine (PhDEAH2) yields a homometallic complex [VO(PhDEA)(PhDEAH)] 1, which reacts with a number of metal alkoxides to afford heterobimetallic oxovanadium(V) complexes of the types [VO(PhDEA)2{M(OR)n-1}] [where PhDEA = C6H5N(CH2CH2O–)2], [M =: Al (n = 3, R = Pri) 2; Al (n = 3, R = But) 3; Ti (n = 4, R = Pri) 4; Zr (n = 4, R = Pri) 5; Nb (n = 5, R = Pri) 6; Ta (n = 5, R = Pri) 7. The derivative [VO(PhDEA)(OSiPh3)] 8 has been prepared by the equimolar interaction of [VO(PhDEA)(OPri)] with Ph3SiOH. All of these complexes have been characterised by spectroscopic (IR; 1H, 13C, 27Al and 51V NMR) studies, elemental analyses, and molecular weight measurements. The derivative 2 has also been characterised by FAB mass spectral studies, which supports for its monomeric nature.

Amino acid/zwitterion equilibria II: vibrational and NMR studies of substituted thiazolidine-4-carboxylic acids

1991 ◽  
Vol 69 (11) ◽  
pp. 1721-1727 ◽  
Author(s):  
H. E. Howard-Lock ◽  
C. J. L. Lock ◽  
M. L. Martins
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Amino Acid ◽  
Carboxylic Acids ◽  
Infrared And Raman Spectra ◽  
Solid Samples ◽  
Nmr Studies ◽  
Nuclear Magnetic Resonance Spectra ◽  
Key Words Amino Acid ◽  
Methyl Derivatives ◽  
Derivatives Of

Infrared and Raman spectra (4000–100 cm) of solid samples of seven different 2-phenyl-, N-benzoyl-, and 2-ethyl-2 methyl derivatives of L-cysteine and D-penicillamine have been observed and assigned. Proton and 13C nuclear magnetic resonance spectra for the compounds have also been measured. Amino acid/zwitterion equilibria are discussed with reference to pK values and the vibrational spectra. Key words: amino acid/zwitterion equilibria, thiazolidine carboxylic acids.

13C NMR studies on trifluoroacetyl derivatives of 2-acetamido-2-deoxyhexoses

1984 ◽  
Vol 22 (11) ◽  
pp. 717-719 ◽  
Author(s):  
M. Ranganathan ◽  
P. Balaram
Keyword(s):  
13C Nmr ◽  
Nmr Studies ◽  
Derivatives Of
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