Investigation of the structure of aminodicarboxylic acids by 13C NMR method

The protonation of ethylenediaminedisuccinic acid was investigated over a wide range of pH by the ¹³C NMR method. The degrees of protonation of the donor groups and the fractions of the trans and gauche conformers in the partially and fully protonated forms of this complexone were determined. A comparison is made of the conformational states of aspartic, iminosuccinic, and ethylenediaminedisuccinic acids. It is shown that complication in the structure has an effect on the conditions of the trans-gauche transitions, which determine the form of the ligand most favorable for combination with the metal ion.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 4, pp. 499–504, July–August, 1989.     

13C NMR spectra and structure of bungeidiol and its transformation products

The results are given of a study of the¹³C NMR spectra of the new terpenoid coumarin bungeidiol (I) and of the products of its transformation (II) and (III) and some model compounds (IV–VII). On the basis of the results obtained from these¹³C NMR spectra and with the use of additive contributions depending on the nature and positions of various substituents (hydroxy and methoxy groups) in the aromatic ring, the structure (I) has been confirmed and a complete assignment of the signals of all the carbon atoms both in the coumarin ring and in the aliphatic part of the molecule of (I) has been made.     

Investigation of the structure and 13C NMR spectrum of 5-phenylbarbituric acid

Crystals of 5-phenylbarbituric acid, 2 , are monoclinic, space group C2/c. There are 8 molecules in the unit cell of dimensions a = 20.218(3), b = 7.477(1), c, = 12.443(2), β = 111.54° and V = 1749.6(4) ų. Full-matrix least-squares refinement has reached R = 0.039. This is the first barbiturate reported to exist in the enol form in the solid state. There is extensive hydrogen bonding between adjacent molecules which gives rise to very dense crystals. The ¹³C-nmr spectroscopy shows that 2 exists in both enol and keto forms in DMSO solution.     

Reaction of the Fischer base with 8-hydroxy-1-naphthaldehydes. Investigation of the reaction products by 13C NMR spectroscopy

The product of the condensation of the Fischer base with unsubstituted 8-hydroxy-1-naphthaldehyde is a bisindolinespirooxepine. 5,7-Dinitro-8-hydroxy-1-naphthaldehyde reacts with the Fischer base to give a merocyanine that does not display a tendency to undergo conversion to the cyclic form. 2H-Naphtho[1,8-bc]furan derivatives are formed in the reaction of the Fischer base with 5-nitro-, 5-bromo-, and 5,7-dibromo-8-hydroxy-1-naphthaldehydes. The structures of the compounds obtained were established on the basis of data from the PMR and ¹³C NMR spectra. It was shown by means of the ¹³C NMR spectra that the product of the condensation of phthalic monoaldehyde with the Fischer base is not a seven-membered spirolactone, as previously assumed, but rather a phthalide derivative.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1501–1506, November, 1982.     

Protein structure determination from 13C spin-diffusion solid-state NMR spectroscopy

Proton-driven 13C spin diffusion (PDSD) is a simple and robust two-dimensional NMR experiment. It leads to spectra with a high signal-to-noise ratio in which cross-peaks contain information about internuclear distances. We show that the total information content is sufficient to determine the atomic-resolution structure of a small protein from a single, uniformly 13C-, 15N-labeled microcrystalline sample. For the example of ubiquitin, the structure was determined by a manual procedure followed by an automatic optimization of the manual structure as well as by a fully automated structure determination approach. The relationship between internuclear distances and cross-peak intensities in the spectra is investigated.     

Theoretical investigation of the 1,3-migration of hydrogen in the telomerization of ethylene and propylene with methanol

Semiempirical quantum-chemical calculations by the MINDO/3 method have been carried out with complete optimization of the geometry of all the radicals in the molecules which take part in the telomerization of ethylene and propylene with methanol. For each of the telomerization processes the transition states have been determined for three competing reactions: 1,3-H-migration, chain transfer, and chain growth. It is concluded by a comparison of the heat effects and the potential barriers that 1,3-H-migration is possible for the telomerization of propylene, but improbable for the telomerization of ethylene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2017–2024, September, 1990.     

13C NMR Investigation of Si-alkylsubstituted 1,3,5-Trisilacyclohexanes

¹³C NMR spectra of Si-alkylsubstituted derivatives of 1,3,5-trisilacyclohexanes have been recorded and analyzed. A systematic preparation of alkyl derivatives with mixed substituents made it possible to evaluate substituent-induced chemical shift (SCS) values for the ring carbon atoms in β and δ position. It is found that the β_e effect decreases in the order Me > Et > i-Pr > t-Bu. For the alkyl groups Me, Et, and i-Pr the β_a effect is smaller than the β_e effect. Axial SCS values for the t-Bu group are not accessible because chair conformations with an axial t-Bu group are unfavourable and tend to escape into a twisted boat form. The observed δ effects are small and do not show any obvious tendencies.     

1 H and 13 C NMR spectra and structure of 2-trichloromethyl-4-methylene-1,3-dioxolanes

The ¹H and ¹³C NMR spectra of a number of 5-substituted 2-trichloromethyl-4-methylene-1,3-dioxolanes were studied. It was observed that the exocyclic double bond is in effective conjugation with the 3–0 ring atom. The configuration of the substituents was established, and a conformational model of these heterocycles of the envelope type with the 1–0 atom deviating from the plane in which the remaining ring atoms are situated is proposed. The applicability of the ¹³C NMR spectra for the determination of the configuration of the compounds is demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1176–1180, September, 1976.     

13C and1H NMR spectra and structure of 2-aryl-1,3-dibenzoyl-1,3-diazabicyclo[3.3.1]nonanes

Conclusion ¹³C and¹H NMR spectroscopy was used to determine the structures of 2-aryl-1,3-dibenzoyl-1, 3-diazabicyclo[3.3.1]nonanes and 2-aryl-1-benzyl-3-benzoyl-1,3-diazabicyclo[3.3.1]nonane. These compounds were found to exist predominantly in the boat-chair conformation (boat for the diaza ring), while the 2-aryl substituents occupy the exo or endo position.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1023–1028, May, 1988.     

Study of the structure of calcichrome by means of13C NMR spectroscopy

The structure of a reagent known under the trade name Calcion-Calcichrome has been investigated in solution and in the solid phase by means of¹³C NMR spectroscopy. It has been shown that the actual structure of the reagent differs from those that had been postulated previously.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2775–2779, December, 1991.