Analogues of DIOP. Synthesis, reactivity, and NMR behaviour

The (4R,5R)-4,5-Bis(diphenylphosphinomethyl)-2-(-naphthoxy)-1,3,2-dioxaphospholane (1) and (4R,5R)-4,5-bis(diphenylphosphinomethyl)-2-dimethylamino-2-oxo-1,3,2-dioxaphospholane (2), analogues of the chiral bisphosphine ligand DIOP, have been synthesized. Both compounds have a second phosphorus functionality in the backbone of the chiral bisphosphine. That the reactivities of the various phosphorus atoms in 1 are different was shown for the reaction with BH₃. The complexation behaviour of 1 towards Rh^I was studied with the aid of ³¹P NMR spectroscope.     

The NMR investigation of alkaloids. IX.13C NMR spectra and stereochemistry of convolvine,convolamine, convoline,convolidine, subhirsine,and 6-hydroxyhyoscyamine

On the basis of the results of a study of the¹³C NMR spectra, a correlation has been made of the CSs of the¹³C carbon nuclei with the structure and stereochemistry of the tropane alkaloids convolvine, convolamine, convoline, convolidine, subhirsine, and 6-hydroxyhyoscyamine. It has been established that the N-CH₃ group in convolamine and the N-OH group in convoline are oriented equatorially, and the N-CH₃ in hydroxyhyoscyamine axially.Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 80–84, January–February, 1986.     

A study of sesquiterpene lactones by13C NMR spectroscopy. II.13C NMR spectra of alkhanin,acetylartemisin, and tauremisin

The¹³C NMR spectra of alkhanin, acetylartemisin, and tauremisin have been studied.     

NMR spectra of cyclic nitrones. 4. Synthesis and 13C NMR spectra of 4H-imidazole N-oxides and N,N-dioxides

4H-Imidazole 1,3-dioxides and 4H-imidazole 3-oxides were obtained by oxidation of 1-hydroxy-3-imidazoline 3-oxides and 1-hydroxy-3-imidazolines with lead and manganese dioxides or the stable nitroxyl radical, while 4H-imidazole 1-oxides were obtained by thermal decomposition of 1-acetoxy-3-imidazoline 3-oxides. Facile oxidation of the ethyl group in 5-ethyl-4H-imidazole 1,3-dioxide and the formation of 5-acetyl-4H-imidazole 1,3-dioxide and 5-acetyl-4H-imidazole 3-oxide were observed. It is shown that a strictly determined region of chemical shifts of the C(₂), C(₅), and C(₄) atoms is characteristic for each group of 4H-imidazole N-oxides in the ¹³C NMR spectra; this makes it possible to clearly establish the position of the N-oxide oxygen atom.See [1] for Communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1640–1648, December, 1988.     

NMR investigation of alkaloids. XI.13C NMR spectra and structure of codonopsine and codonopsinine

An assignment of the signals in the¹³C NMR spectra of the alkaloids codonopsinine and codonopsine has been made on the basis of selective double heteronuclear resonance experiments. Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 536–538, July–August, 1989.     

Cyclische,gekreuzt-konjugierte Bindungssysteme. XIII. NMR.-untersuchungen am Phenafulven-system

The HNMR. spectra of phenalene, phenalenone, of some protonated and alkylated derivatives and the spectra of some substituted phenafulvenes are discussed and very qualitatively correlated with the π-electron distribution in some of these systems.     

NMR study of organosilicon compounds. III—Silicon-29, nitrogen-14, carbon-13 and proton NMR spectra of silylakylamines

²⁹Si, ¹⁴N ¹³C and ¹H NMR data are presented for a series of homologous (methylethoxysilyl)alkylamines of the type (CH₃)_3?n(C₂H₅O)_nSi(CH₂)_mNH₂(n=o to 3; m = 1 to 4). The measured ¹³C and ¹H chemical shifts correlate with the total net charges Q_A on the corressponding atoms, estimated by the Del Re method. ¹⁴N and ²⁹Si chemical shifts which do not show simple linear relationships to the charges are found to correlate with the relative basicities of the compounds. The influence of the remote substituent (? NH₂ and others) on the ₂₉Si chemical shifts is shown to depend on the number and nature of substituents directly on the silicon atom. Argyments for d-orbital participation in the Si? O bounds are given. The chemical shifts of ²⁹Si, ¹⁴N and ₁₃C nuclei are not consistent with the fromation of intramolecular ‘long bonds’ between the solicon and nitrogen atoms in aliphatic silymethylamines.     

Spiro beta-lactams as beta-turn mimetics. Design, synthesis, and NMR conformational analysis

Molecular modeling calculations using high-level ab initio methods (MP2/6-31+G) of a new type of spiro beta-lactams predict that these systems could adopt a beta-turn secondary structure in solution. Strong intramolecular hydrogen bonds stabilize the beta-turn conformation with a geometry that is very close to the ideal type II beta-turns. The synthesis of the spiro beta-lactams is achieved by Staudinger reaction of a cyclic ketene derived from N-bencyloxycarbonyl-L-proline acid chloride with an imine. This reaction allows the formation of the spiranic backbone in a single-step with high diastereoselectivity and good yields. The new spiro beta-lactams obtained are the core for the preparation of different types of peptidomimetics using well-established peptide chemistry. The NMR conformational analysis shows that these compounds adopt beta-turn conformation as predicted by the theoretical studies.     

Protonization of purine, adenine, and guanine. NMR spectra and structure of mono, di, and tri cations

Proton NMR. spectra of purine, adenine, guanine and methylsubstituted guanines have been measured in CF₃COOH, FSO₃H and FSO₃H? SbF₅? SO₂ at 27° and low temperatures. These conditions permit to study multiple protonation of purines, using chemical shifts of CH, NH and OH protons. The spectra of mono-, di- and tri-cations are described and fully assigned.     

Nitrogen-containing organosilicon compounds. 151. Synthesis,NMR spectra,and biological activity of hetarylaminoalkylsiloxanes and their hydrochlorides and methiodides

Hetarylaminoalkylsiloxanes and their hydrochlorides and methiodides were synthesized. Their neurotropic, antitumorigenic, and antimicrobial properties were studied. It was established that the character of the heteroring, the number of siloxy groups, and the length of the methylene chain between the nitrogen and silicon atoms in the molecule affect the biological activity. It is shown that the changes in the chemical shifts in the ¹³C, ¹⁵N, ¹⁷O, and ²⁹Si NMR spectra of the synthesized compounds are determined chiefly by the presence of siloxy substituents, i.e., the effects in the Si-O-Si fragment prevail.See [1] for communication 150.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1653–1664, December, 1991.