15N-NMR Spectroscopy. XVIII. Sequence Analysis of Linear Polyureas

Various homo- and copolyureas were prepared either by conversion of diamines with diisocyanates or by heating diamines with N, N'-bisphenoxycarbonyl diamines. The ¹³C-NMR spectra and the natural abundance ¹⁵N-NMR spectra were measured in trifluoroacetic acid. In contrast to polyamides, the carbonyl signals of polyureas are not sensitive to neighboring residue effects, so that ¹³C-NMR spectra are in most cases useless for the sequence analysis of copolyureas. The ¹⁵ N-NMR signals of urea groups are, however, sensitive to the influence of both substituents and thus contain information on the sequence. Structure/ shift-relationships are discussed, and ¹⁵ N-NMR spectra of various copolyureas are presented.     

Characterization of organometallic polymers by 13C- and 119Sn-NMR: Configurational/compositional triads in poly(tri-n-butyltin methacrylate/methyl methacrylate)

The 1:1 and 2:1 formulations of the free radical initiated copolymers of methyl methacrylate (MMA) and tri-n-butyltin methacrylate (TBTM), and the homopolymer, poly(TBTM), are characterized by ¹³C- and ¹¹⁹C-NMR structural analyses were performed on the tributyltin-free hydrolyzate, a copolymer of MMA and methacrcylic acid (MAA). Configurational sequencing at the triad level is performed using the α-methyl region of the ¹³C-NMR spectrum. The probability of isotactic (meso) dyad placement at 80°C in the homopolymer (0.19) is determined to be significantly less than the probabilities observed for the copolymers (0.23–0.24). Random compositional sequencing is established for the copolymers through a comparison of the carbonyl regions of the ¹³C-NMR spectra of the hydrolyzates with the carbonyl regions in published spectra of structurally characterized copolymers of MMA and MAA. The ¹¹⁹Sn chemical shift and the tin-carbon J coupling for the polymers are dependent on the solvent employed. This dependence is attributed to electron donor or acceptor interactions between the solvent and the strong Sn? O dipole. The tin-containing copolymers exhibit multiple ¹¹⁹Sn resonances, which appear related to compositional sequencing.     

1H- und 13C-NMR.-Spektroskopie der Nonadride

¹H- and ¹³C-NMR. Spectroscopy of the Nonadrides The ¹H- and ¹³C-NMR. spectra of the nonadrides glaucanic acid ( 1 ), glauconic acid ( 2 ), heveadride ( 3 ), byssochlamic acid ( 4 ), scytalidin ( 5 ), rubratoxin A ( 6 ), and rubratoxin B ( 7 ) have been measured. Partial decoupling experiments permitted assignment of the majority of the signals.     

Infrared spectroscopic analysis of poly(methyl acrylate-co-styrene)

Methyl acrylate–styrene copolymers of different copolymer compositions were free-radically prepared. The relative intensities of the carbonyl frequencies of the methyl acrylate units at v 1730 cm^?1 were correlated with the copolymer composition. The positions and shapes of the carbonyl bands in the infrared absorption spectra of the copolymers-dissolved in chloroform, were shown to depend on the composition of the copolymers and upon the presence of different proportions of methyl acrylate centered triads. The results obtained by infrared spectroscopy were compared with those obtained by ¹³C-NMR. Infrared spectra may be used to yield information about both the copolymer composition and the triad sequence distribution.     

Über die Temperaturabhängigkeit der 13C-NMR.-Spektren von [5–6-η-(1Z, 5E)-Cyclooctadien]tetracarbonyleisen und (1Z, 5E)-Cyclooctadien

On the Temperature Dependence of the ¹³C-NMR. Spectra of [5-6-η-(1Z,5E)-Cyclooctadien] and of (lZ, 5E)-Cyclooctadiene The activation parameters of the conformational ring inversion process (simultaneous rotation around the C(3), C(4) and C(7), C(8) bonds; cf. Scheme 1) of the title compounds ( 1 and 2 , respectively) have been determined between 275 L and 155 K by a complete line shape analysis of the temperature dependent proton noise-modulated decoupled ¹³C-NMR. spectra of 1 and 2 . The temperature dependence of the rates (k( 1 ) and k( 2 ), respectively) of the inversion process can be described by the following equations (no influence of the solvents was observed; E_a in J/mol): . Further data are given in Tables 1 and 2. The carbonyl groups of the complex 1 show at 180 K , where the ring inversion process is frozen out, a single line at 211 ppm, i. e. the coalescence temperature of the carbonyl groups must be < 180 K .     

Notiz über die Reaktion von Methylhydrazin mit N-Cyano-azomethinen. Abhängigkeit des Reaktionsverlaufs von der Natur der Abgangsgruppe

The reaction of methylhydrazine with N-cyanoazomethines 1 containing a thioalkyl leaving group yields the 3-amino-1,2,4-triazole derivatives 2 , whereas the N-cyanoazomethines 1 containing an alkoxy leaving group give the isomeric 5-amino-1,2,4-triazoles 3. The yields are excellent and the position selectivity is high. The structures of the 1,2,4-triazole derivatives were determined with the aid of proton-coupled ¹³C-NMR. spectra.     

13C-NMR.-Spektren von Dicyanhydrochinonen und Dicyan-p-benzochinonen

¹³C-NMR. Spectra of Dicyanohydroquinones and Dicyano-p-benzoquinones The ¹³C-NMR. spectra of 12 dicyanohydroquinones and fully substituted dicyano- and diazido-p-benzoquinones have been measured and assigned by comparison with related benzene and p-benzoquinone derivatives. For p-benzoquinones the influence of the cyano and azido substituents on the chemical shift of the CO-, α- and β-C-atoms has been investigated.     

A 13C-NMR. Study of cis-trans isomeric vitamins A, carotenoids and related compounds.

The ¹H-decoupled ¹³C-NMR. spectra of 35 all-trans, 17 mono-cis vitamin A compounds (acetates, alcohols, aldehydes, acids and esters) and of one 11, 13-di-cis compound (11, 13-di-cis retinol) are reported. Included in this investigation are desmethyl-, desmethylethyl, and aryl-vitamin A analogues and others as well as 30 reference compounds of smaller molecular weight. Furthermore, the ¹³C-NMR. spectra of 23 β-apo- and other carotenoids were studied. A complete assignment of the signals of all 106 compounds to the specific carbon atoms was achieved by extensive application of lanthanide shift reagents, mainly Yb(dpm)₃, by CW-offset and selective ¹H-decoupling experiments, by comparison of the shifts of related compounds, and in three cases by utilization of specifically deuteriated compounds (11, 12-D₂-retinol and retinyl acetate, 15, 15′-D₂-β-carotene). The chemical shift differences between the cis- and trans-vitamin A compounds and the applicability of the shift reagents for the assignment of the ¹³C-NMR. spectra are discussed.     

1H-NMR.-, 13C-NMR.-, UV.- und CD.-Daten von synthetischem (3S, 3′S)-Astaxanthin,seinem 15-cis-Isomeren und einigen analogen Verbindungen

¹H-NMR., ¹³C-NMR., UV. and CD. spectral data of synthetic (3S, 3′S)-astaxanthin, its 15-cis isomer, and some related compounds ¹H-NMR., ¹³C-NMR., UV. and CD. spectra are reported for synthetic (3S, 3′S)-astaxanthin ( 1 ), its 15-cis isomer ( 2 ), its diacetate ( 3 ), and the 15, 15′-didehydro compound ( 5 ). These data prove the identity of the synthetic and the naturally occuring compound 1 . A full interpretation of the ¹H- and ¹³C-NMR. spectra is given and confirms the configuration of all the double bonds. The conformation of the cyclohexene end group of all the compounds is shown to be identical. The signs of the different CD. maxima of 15-cis-astaxanthin are found to be opposite to those of the all-trans compound.     

13C-NMR-spektren von bicyclo[n.1.0]alkenen

The ¹³C-NMR spectra of some bicyclo[3.1.0]hex-3-en-2-ols and of some bicyclo[3.1.0]hex-3-en-2-ones are described. The bond parameters of bicyclo[3.1.0]hex-3-en-2-one are derived from a structure determination of endo-6-methoxy-1,3,6-triphenylbicyclo[3.1.0]hex-3-en-2-one. The electron density is calculated by the EHT method, and correlated with the ¹³C NMR shifts. For comparison the ¹³C NMR spectrum of a bicyclo[4.1.0]hepta-1,5-dione derivative is analysed. The influence of a cyclopropane system attached to a five-membered and to a six-membered ring is elucidated. Whereas the five-membered ring shows conjugation between the carbonyl group and the cyclopropane system, the same effect is not observed in the six-membered ring analogue. This is explained by the highly rigid structure of the five-membered ring.     

Two-Dimensional NMR Studies of Polyene Systems. I. All-trans-Retinal

Two-dimensional (2-D) NMR results are presented for all-trans-retinal. 2-D J-resolved ¹H-NMR separated the multiplets of the olefinic protons and accurately determined their chemical shifts. 2-D shift-correlated ¹H-NMR gave the connectivities between scalar coupled protons. From the observed H,H long-range couplings the assignment of the methyl resonances was possible. 2-D J-resolved ¹³C-NMR separated overlapping C,H-multiplets and allowed analysis of the C,H long-range couplings, 2-D shift-correlated ¹³C-NMR related each directly bonded C,H-pair in this molecule. The potential of 2-D NMR in resolving and identifying individual resonances in polyene spectra is discussed.     

Synthesis and amoebicid properties of emetin analogs. Analysis of the new compounds by 13C-NMR. B/C-cis or trans-fused (+/-) 1-alkyl-3-desethyl-emetin (author's transl)]

Synthesis and amoebicid properties of emetin analogs. Analysis of the new compounds by ¹³C-NMR. B/C-cis or trans-fused (±) 1-alkyl-3-desethyl-emetin. New 1-alkyl-3-desethyl-emetines were prepared for pharmacological purposes. The usual emetine synthesis sequence applied to cis-1-alkylbenzo [a]quinolizidin-2-ones afforded new cis-1-alkyl-3-desethyl-emetines. The trans-fused isomers were also prepared. The relative configuration are determined by ¹H- and ¹³C-NMR. spectra.     

Synthese von [1,2,4]Triazolo [1,5-a]chinazolinen. Ableitung der Konformation von Substituenten mit Hilfe der 13C-NMR.-Spektroskopie

Synthesis of [1,2,4]Triazolo[1,5-a]quinazolines. Assignment of the Conformation of Substituents with the Aid of ¹³C-NMR. Spectroscopy The synthesis of [1,2,4]triazolo[1,5-a]quinazolines by condensation of 2-hydrazinobenzoic acid with N-cyano-imidates is reported. The preferred conformation of substituents at C (5), e.g. N (CH₃)₂, N (CH₃)NH₂, N (CH₃)OH, relative to the aromatic system is deduced with the aid of ¹³C-NMR. chemical shifts and proton nuclear Overhauser effect experiments.     

13N-NMR spectroscopy. XXXV. Sequence analysis of alternating and random copolyamides made up of aliphatic and aromatic ω-amino acids

Alternating copolyamides of various ω-amino acids were synthesized by base-catalyzed polycondensation of N-isothiocyanatoacyl ω-amino acids in solution. Derivatives of the following amino acids were used: glycine, β-alanine, γ-aminobutyric acid, δ-aminovaleric acid, ε-aminocaproic acid, D ,L -β-aminobutyric acid, trans-4-aminocyclohexane 1-carboxylic acid, 4-aminophenyl acetic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, 3-amino-4-methyl benzoic acid, and 4-amino-3-methyl benzoic acid. The base-catalyzed polycondensation at lower temperatures gave purer products than the bulk condensation at 180–200°C. ¹³C-NMR and natural-abundance ¹⁵N-NMR spectra measured in trifluoroacetic acid demonstrate that in most cases undisturbed alternating sequences were obtained. Strong neighboring residue effects and long-range sequence effects were found in the ¹⁵N-NMR spectra, and structure/shift relationships are discussed. The sequences of copolyamides obtained by copolymerizations of lactams or β-amino acid N-carboxyanhydrides were investigated by both ¹⁵N-NMR and ¹³C-NMR spectroscopy. ¹³C-NMR spectroscopy was found to be more useful if the copolyamides consist of ω-amino acid units of different chain length. However, ¹⁵N-NMR spectroscopy is more suited if the monomer units differ exclusively by their substituents.     

Biosynthesis of the cytochalasans. Part III. C-NMR. of cytochalasin B (phomin) and cytochalasin D. Incorporation of [1-13C]- and [2-13C]-sodium acetate

Sequential single frequency decoupling and partially relaxed Fourier transform (PRFT) are used to assign the natural abundance ¹³C-NMR. spectra of cytochalasin B (phomin) ( 1 ) and cytochalasin D ( 2 ). Cultures of Phoma spec. S 298 were fed [2-¹³C]-sodium acetate, and the distribution of this precursor in cytochalasin B (phomin) ( 1 ) was determined by ¹³C-NMR. spectroscopy. Likewise, the labelling patterns in cytochalasin D (zygosporin A) ( 2 ) from Zygos-posium masonii could be identified after incorporation of [2-¹³C]-sodium acetate and [l-¹³C]-sodium acetate. The results confirm previous proposals for the biogenesis of the cytochalasans from phenylalanine, methionine, and a C₁₈, or C₁₆, polyketide part.     

13C-NMR.-Spektren von 3H-Benz[cd]azulen-3-onen

¹³C-NMR. Spectra of 3H-benz[cd]azulenc-3-ones ¹³C-NMR. Spectra of 7,9-dimethyl-3H-benz[cd]azulenc-3-one ( 2 ) and 7,9-dimethyl-4,5-dihydro-3H-benz[cd]azulene-3-one ( 7 ) in CDCl³ and CF₃CO₂D are reported. The assignment of signals was achieved with the aid of selective proton decoupling, non-decoupled spectra and comparison with spectra of simple azulene-derivatives. The major localization of positive charge in the cationic 3-hydroxybenz-[cd]azulenium system was found in the six- and seven-membered ring, which suggests in accordance with calculated π-electron densities the structure of a benztropylium ion rather than a bridged azulenium ion.     

13C-NMR. Spectral Differences between Corresponding Methyl Esters,Phenyl Esters and 2-Substituted Chromones

The ¹³C-NMR. spectra of 2-substituted chromones ( 3 ) are compared with the data of the analogous methyl and phenyl esters ( 1 and 2 ). The chemical shift differences found are most prominent for the C-atoms in β-position to the ester carbonyl and chromone C(2), respectively. These shift differences are discussed in terms of conformational differences between the esters 1 and 2 and the analogous chromones 3 .     

Substituenteneffekte auf die NMR-Spektren von Pentafulvenen. (13C, 13C)-NMR-Kopplungskonstanten (1J(C,C))

Substituent Effects on NMR Spectra of Pentafulvenes. ¹³C, ¹³C-NMR Coupling Constants (¹J(C, C)) ¹H- and ¹³C-NMR spectra of 6-monosubstituted pentafulvenes 1 – 8 have been analysed, and ¹J(C, C) coupling constants have been determined from ID-inadequate spectra of ¹³C satellites. It turns out that ¹³C,¹³C coupling constants of the ring C-atoms, and especially J(1,2)/J(3,4) and J(2,3), reflect the extent of π delocalisation in the fulvene ring. With increasing electron-donating capacity of the substituent R, J(1,2)/J(3,4) values are decreasing, while J(2,3) (and J(1,5)/J(4,5) as well) are increasing, and linear correlations of Hammett substituent constants σ⁺ and ¹J(C,C) values are obtained.     

Preparation of Chiral Hydroxy Carbonyl Compounds and Diols by Ozonolysis of Olefinic Isoborneol and Fenchol Derivatives: Characterization of Stable Ozonides by 1H-, 13C-, and 17O-NMR and Electrospray Ionization Mass Spectrometry

The allylic and homoallylic alcohols 1 – 8 , prepared from (+)-camphor and (−)-fenchone, were ozonized in Et₂O at −78° and treated with Et₃N or LiAlH₄ to give the chiral hydroxy carbonyl compounds 9 – 16 and the diols 17 – 24 , respectively (Scheme 1). In the case of the diols 19 and 24 , the formation of new chiral centers proceeded with high diastereoselectivity. These diols were prepared highly diastereoselectively also by LiAlH₄ reduction of the hydroxy carbonyl compounds 11 and 16a , respectively (Scheme 2). The absolute configuration of the new chiral centers in 19 and 24 was determined by X-ray and NMR methods. The ozonization of compounds 2 , 3 , 7 , and 8 provided the relatively stable hydroxy-substituted 1,2,4-trioxolane derivatives (ozonides) 37 – 40 (Scheme 5) which were characterized by ¹H- and ¹³C-NMR spectra, ESI-MS, and natural-abundance ¹⁷O-NMR spectra.     

13C-NMR.-Substituenteninkremente der N3-Gruppe in Azido-1,4-benzochinonen

¹³C-NMR. Substituent Increments of the Azido-group in 1,4-Benzoquinones The empirical substituent increments of the azido-group in 1,4-benzoquinones have been derived from the ¹³C-NMR. chemical shifts of 2-azido-5-chloro-1,4-benzoquinone. The validity of the obtained values was tested by comparison of the empirical and computed ¹³C-NMR. chemical shifts of other azido-chloro-1,4-benzoquinones.