Chiroptical properties and conformation of N-acetyl-L-amino acids N'-methylamides with aliphatic side chains

1983 ◽  
Vol 48 (10) ◽  
pp. 2844-2861 ◽  
Author(s):  
Petr Maloň ◽  
Petr Pančoška ◽  
Miloš Buděšínský ◽  
Jan Hlaváček ◽  
Jan Pospíšek ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Solvent Polarity ◽  
Helical Conformation ◽  
Experimental Conditions ◽  
Chiroptical Properties ◽  
H Nmr ◽  
Fluorinated Alcohols ◽  
Conformational Equilibria ◽  
Φ Angle ◽  
Conformational Distribution

CD and 1H NMR spectra of L-alanine (I), L-leucine (II), L-valine (III) and L-tert-leucine (IV) N-acetyl N'-methylamides were measured at various experimental conditions involving changes of temperature, concentration and solvent polarity. The least flexible tert-leucine derivative IV exists predominantly either in right handed α-helical (αR) conformation (fluorinated alcohols, ethanol) or in extended (C5) conformation (cyclohexane, acetonitrile). In this compound the Φ angle is constrained to about -120°, excepting aqueous solution. The flexible amides I and II exhibit more complex conformational equilibria involving probably the 310, αR and C5 conformations. The 310 helical conformation is favoured in water, acetonitrile and non-fluorinated alcohols, while a higher participation of αR conformation is observed in strongly polar fluorinated alcohols. Conformational distribution of the valine derivatve III is similar to IV in fluorinated alcohols and to amides I and II in other solvents. The C7eq conformation is clearly detected only in cyclohexane solutions of non-associated forms of I and II.

Optically active tricyclic dilactams with non-planar cis-amide groups: Synthesis, X-ray, NMR and CD studies

1982 ◽  
Vol 47 (3) ◽  
pp. 1000-1019 ◽  
Author(s):  
Karel Bláha ◽  
Miloš Buděšínský ◽  
Zdena Koblicová ◽  
Petr Maloň ◽  
Miloš Tichý ◽  
...  
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
Condensation Reaction ◽  
Spatial Arrangement ◽  
Coupling Constants ◽  
X Ray Diffraction ◽  
Chiroptical Properties ◽  
X Ray ◽  
H Nmr ◽  
Cd Studies

Three tricyclic dilactams were investigated as models for study of chiroptical properties of homoconjugated non-planar cis-amide groups. Racemic 5,8-diazatricyclo[6,3,0,01,5]undecane-4,9-dione (I) was partially resolved into enantiomers by chromatography on acetylcellulose. The 6-isobutyl (II) and 6-methyl (III) derivatives were prepared in optically pure forms by condensation of diethyl 4-oxoheptanedioate with (S)-1,2-diamino-4-methylpentane and (S)-1,2-diamino-propane, respectively. The respective diamines were synthesized starting from (S)-leucine and (S)-alanine: this determined the absolute configuration on the C(6) atom in both dilactams. As shown by 1H and 13C NMR spectra, the condensation reaction afforded only one of the two possible diastereoisomeric dilactams. The configurational relation between the chiral center at C(6) and the chirality of the tricyclic moiety was derived from coupling constants in the 1H NMR spectra. The configuration of compound II was confirmed by X-ray diffraction. According to 1H NMR spectra, the spatial arrangement of II in solution is similar to that in crystal, the only difference being in the local conformation of the isobutyl side chain at C(6). IR spectroscopy identified only minor differences in geometry of the two lactam groupings in II and III. All CD parameters of compounds I-III, measured in various solvents, are very similar. The CD curves show the same absolute configuration (1S, 6S) of compounds II and III and the opposite configuration of the studied enantiomer of I(1R). Parameters of the n-π dichroic band indicate a non-planar amide-grouping whose geometry is known from the X-ray analysis. Its sign agrees with the relationship derived for the chiroptical properties of defined pyramidicity on nitrogen atom in non-planar amides. The π-π dichroic bands exhibit an exciton splitting into a couplet as a result of interaction between the amide groups.

Conformational structure of ethylene glycol dibenzoate. Vibrational and NMR spectra

1981 ◽  
Vol 46 (8) ◽  
pp. 1913-1929 ◽  
Author(s):  
Bohdan Schneider ◽  
Pavel Sedláček ◽  
Jan Štokr ◽  
Danica Doskočilová ◽  
Jan Lövy
Keyword(s):  
Ethylene Glycol ◽  
Vibrational Spectra ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
Conformational Structure ◽  
Infrared And Raman Spectra ◽  
H Nmr ◽  
Liquid States ◽  
Crystalline Forms ◽  
C Nmr

It was found that three crystalline forms of ethylene glycol dibenzoate can be prepared. Infrared and Raman spectra of these three forms, as well as of the glassy and liquid states, were measured. From 3JHH coupling constants obtained by analysis of the 13C satellite band of the -CH2- group in 1H NMR spectra, and from the 3JCH coupling constants of the -CO.O.CH2- fragment obtained by analysis of the carbonyl band in 13C NMR spectra it was found that in the liquid state the -CH2-CH2- group exists predominantly in the gauche conformational structure, and the bonds C-O-C-C assume predominantly a trans orientation. The results of the analysis of NMR and vibrational spectra were used for the structural interpretation of conformationally sensitive bands in vibrational spectra of ethylene glycol dibenzoate.

Preparation and absolute configuration at C(20) of 21-nor-5α-chol-22-en-24→20-olide derivatives

1981 ◽  
Vol 46 (4) ◽  
pp. 917-925 ◽  
Author(s):  
Vladimír Pouzar ◽  
Miroslav Havel
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
Lithium Salt ◽  
H Nmr ◽  
Chemical Correlation ◽  
Unsaturated Lactones

Reaction of the aldehyde I with the lithium salt of 1-(2-tetrahydropyranyloxy)-2-propyne yielded the compounds II and IV. From the compound II the lactone XII was prepared via the intermediates III and X, the lactone XVIII was prepared from the substance IV via the intermediates V and XVI. The unsaturated lactones XII and XVIII were also prepared by sulfenylation and dehydrosulfenylation of the saturated lactones XIII and XIX. Based on chemical correlation and 1H-NMR spectra analyses of the compounds II and IV, the lactone XII was assigned the 20R-configuration whereas the lactone XVIII was allotted the 20S-configuration.

New type of addition to 5-substituted 4-arylidene-2-(4,5-dihydrofurfurylidene)-N,N-dimethyliminium bisperchlorates. Preparation of 4-substituted 5-(N,N-dimethylamino)-2-furancarbaldehydes

1986 ◽  
Vol 51 (3) ◽  
pp. 573-580 ◽  
Author(s):  
Tibor Gracza ◽  
Zdeněk Arnold ◽  
Jaroslav Kováč
Keyword(s):  
Nmr Spectra ◽  
Addition Reaction ◽  
H Nmr ◽  
Organic Bases ◽  
New Type

4-Arilidene-5-(N,N-dimethyliminium)-2-(4,5-dihydrofurfurylidene)-N,N-dimethyliminium bisperchlorate I undergoes a 1,4-addition reaction with organic bases under re-formation of the furan nucleus; this behaviour has been utilized in the preparation of new 4-substituted 5-(N,N-dimethylamino)-2-furancarbaldehydes II, III. The structure of the prepared compounds has been confirmed by 13C and 1H NMR spectra.

Preparation, properties and structure of some intermediate nido- and arachno-monocarbaboranes

1981 ◽  
Vol 46 (10) ◽  
pp. 2345-2353 ◽  
Author(s):  
Karel Baše ◽  
Bohumil Štíbr ◽  
Jiří Dolanský ◽  
Josef Duben
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Nmr Spectra ◽  
Liquid Ammonia ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Starting Compound

The 6-N(CH3)3-6-CB9H11 carbaborane reacts with sodium in liquid ammonia with the formation of 6-CB9H12- which was used as a starting compound for preparing the 4-CB8H14, 9-L-6-CB9H13 (L = (CH3)2S, CH3CN and P(C6H5)3), 1-(η5-C5H5)-1,2-FeCB9H10-, and 2,3-(η5-C5H5)2-2,31-Co2CB9H10- carboranes. The 4-CB8H14 compound was dehydrogenated at 623 K to give 4-(7)-CB8H12 carborane. Base degradation of 6-N(CH3)3-6-CB9H11 in methanol resulted in the formation of 3,4-μ-N(CH3)3CH-B5H10. The structure of all compounds was proposed on the basis of their 11B and 1H NMR spectra and X-ray diffraction was used in the case of the transition metal complexes.

The preparation of 3-amino-3-deoxy-1,2-O-isopropylidene-α-L-erythrofuranose, 3-amino-3-deoxy-1,2-O-isopropylidene-β-D-threofuranose and their derivatives

1980 ◽  
Vol 45 (12) ◽  
pp. 3378-3390 ◽  
Author(s):  
Jiří Jarý ◽  
Milena Masojídková ◽  
Ivan Kozák ◽  
Miroslav Marek ◽  
Jan Staněk
Keyword(s):  
Nucleophilic Substitution ◽  
Sodium Azide ◽  
Sodium Benzoate ◽  
Nmr Spectra ◽  
Subsequent Reduction ◽  
H Nmr ◽  
Amino Derivatives

The title amino derivatives VI and XIV were prepared by nucleophilic substitution of p-toluenesulfonyl derivatives II and XVII with sodium azide or hydrazine and subsequent reduction. Nucleophilic substitution of compounds II and XVII with sodium benzoate was also investigated. The 1H NMR spectra of the substances prepared are discussed.

Preparation of (20E)-21-Ethoxycarbonyl-14β,17α-pregna-5,20-dien-3β-yl Hydrogen Butanedioate

1995 ◽  
Vol 60 (4) ◽  
pp. 715-718 ◽  
Author(s):  
Vladimír Pouzar ◽  
Ivan Černý
Keyword(s):  
Title Compound ◽  
Nmr Spectra ◽  
Total Yield ◽  
Reaction Sequence ◽  
Pregnane Series ◽  
H Nmr

The title compound X was prepared according to the recently published procedure for preparation of analogous derivatives in the 5β-pregnane series, using the reaction sequence I -> II -> III -> IV -> V -> VI -> VII -> VII -> IX -> X (total yield 18%). The configuration at ring D centers (14β,17α) follows from the structure of the starting ketone I and was also checked by comparing diol IV with the sample prepared by an independent route. The epimeric purity at C-17 was carefully monitored during the whole synthesis by 1H NMR spectra (singlet of 18-H3).

119Sn, 13C and 1H NMR Spectra of Tris(1-butyl)stannyl D-Glucuronate

1997 ◽  
Vol 62 (8) ◽  
pp. 1169-1176 ◽  
Author(s):  
Antonín Lyčka ◽  
Jaroslav Holeček ◽  
David Micák
Keyword(s):  
Chemical Shift ◽  
Carbonyl Group ◽  
1H Nmr ◽  
Equatorial Plane ◽  
Title Compound ◽  
Nmr Spectra ◽  
Hydroxyl Groups ◽  
Carboxylic Group ◽  
H Nmr ◽  
Oxygen Atoms

The 119Sn, 13C and 1H NMR spectra of tris(1-butyl)stannyl D-glucuronate have been measured in hexadeuteriodimethyl sulfoxide, tetradeuteriomethanol and deuteriochloroform. The chemical shift values have been assigned unambiguously with the help of H,H-COSY, TOCSY, H,C-COSY and 1H-13C HMQC-RELAY. From the analysis of parameters of 119Sn, 13C and 1H NMR spectra of the title compound and their comparison with the corresponding spectra of tris(1-butyl)stannyl acetate and other carboxylates it follows that in solutions of non-coordinating solvents (deuteriochloroform) the title compound is present in the form of more or less isolated individual molecules with pseudotetrahedral environment around the central tin atom and with monodentately bound carboxylic group. The interaction of tin atom with oxygen atoms of carbonyl group and hydroxyl groups of the saccharide residue - if they are present at all - are very weak. In solutions in coordinating solvents (hexadeuteriodimethyl sulfoxide or tetradeuteriomethanol), the title compound forms complexes with one molecule of the solvent. Particles of these complexes have a shape of trigonal bipyramid with the 1-butyl substituents in equatorial plane and the oxygen atoms of monodentate carboxylic group and coordinating solvent in axial positions.

A 15N, 13C, and 1H NMR study of reaction products from arylguanidines and chloroformate esters

1991 ◽  
Vol 56 (7) ◽  
pp. 1505-1511 ◽  
Author(s):  
Antonín Lyčka ◽  
Karel Palát
Keyword(s):  
1H Nmr ◽  
Nmr Spectra ◽  
Reaction Products ◽  
H Nmr ◽  
Nmr Study

The 15N, 13C, and 1H NMR spectra of the reaction products from arylguanidines with two mols of chloroformate esters have been measured. With application of the corresponding 15N isotopomer it has been proved that the reaction products have the structures IIIa-IIIc.

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