L. M. Khalilov

How reliable are GIAO calculations of 1H and 13C NMR chemical shifts? A statistical analysis and empirical corrections at DFT (PBE/3z) level.

Reliability of calculated 1H and 13C NMR chemical shifts for various classes of organic compounds obtained with gauge‐invariant atomic orbital (GIAO) approach has been studied at the PBE/3ζ level (as implemented in PRIRODA code) using linear regression analysis with experimental data. Empirical corrections for the calculated chemical shifts δH,calc = δPBE/3ζ − 0.08 ppm (RMS 0.18 ppm, MAD 0.66 ppm) and δC,calc = δPBE/3ζ − 6.35 ppm (RMS 3.09 ppm, MAD 9.42 ppm) have been developed using the sets of 263 and 308 experimental values for 1H and 13C chemical shifts, respectively. The confidence intervals of NMR chemical shifts at 95% confidence probability are δH,calc ± 0.35 ppm for 1H and δC,calc ± 6.05 ppm for 13C.

Phytoecdysteroids from the juice of Serratula coronata L. (Asteraceae)

Seven phytoecdysteroids have been isolated from Serratula coronata L. One of them is a new phytoecdysteroid, 3-epi-20-hydroxyecdysone. Two further ecdysteroids, 20-hydroxyecdysone 22-acetate and taxisterone, are isolated from this species for the first time in addition to the typical S. coronata ecdysteroids, 20-hydroxyecdysone, ecdysone, ajugasterone C and polypodine B. The juice squeezed from aerial parts of fresh plants of S. coronata was extracted with ethyl acetate. The ecdysteroids were isolated by a combination of chromatographic techniques (mainly HPLC) and identified by 1D and 2D (1)H and (13)C NMR experiments and mass-spectrometry. The biological activities of 3-epi-20-hydroxyecdysone (EC(50)=1.6 x 10(-7) M), taxisterone (EC(50)=9.5 x 10(-8) M) and ajugasterone C (EC(50)=6.2 x 10(-8) M) have been determined in the Drosophila melanogaster B(II) bioassay for ecdysteroid agonist activity.

Identification and Biological Activity of Volatile Organic Compounds Emitted by Plants and Insects. IV. Composition of Vapor Isolated from Certain Species of Artemisia Plants

The components of fragrance from four wormwood species of theArtemisiaL. genus were analyzed by GC-MS. The major and minor components of volatile essential oils typical of the studied plant species were determined.

PMR and 13C NMR Spectra of Biologically Active Compounds. XII. Taraxasterol and Its Acetate from the Aerial Part of Onopordum acanthium

Crystalline taraxasterol and its acetate were isolated for the first time from Onopordum acanthium. Two-dimensional COSY, HSQC, and HMBC NMR experimentswere carried out forcomplete assignment of signals in the PMR and 13C NMR. Chemical shifts of stereochemically important methyl C atoms C-28 and C-29 were measured.

Effective synthesis of N-aryl-substituted 1,5,3-dithiazepinanes and 1,5,3-dithiazocinanes

Selective methods were developed for the synthesis of N-aryl-1,5,3-dithiazepinanes and N-aryl-1,5,3-dithiazocinanes by transamination of N-tert-butyl-1,5,3-dithiazepinane or recyclization of 1-oxa-3,6-dithiacycloheptane and 1-oxa-3,7-dithiacyclooctane by the action of aniline derivatives in the presence of Sm(NO3)3·6H2O catalyst.

1H and 13C NMR chemical shift assignments of spiro-cycloalkylidenehomo- and methanofullerenes by the DFT-GIAO method.

The 1H and 13C NMR chemical shifts of spiro‐cycloalkylidene[60]fullerenes were assigned using experimental NMR data and the Density Functional Theory (DFT)–Gauge Independence Of Atomic Orbitals method (GAIO) calculation method in the Perdew Burke Ernzerhof (PBE)/3z approach. The calculated values of the 13C NMR chemical shifts adequately reproduce the experimental values at this quantum chemistry approach. Similar assignments will be helpful for 13C NMR spectral analysis of homo‐ and methano[60]fullerene derivatives for structure elucidation and to determine the influence of fullerene frames on substituents and the influence of substituents on fullerene cores. Copyright

Ozonolysis of Alkenes and Study of Reactions of Polyfunctional Compounds: LXVI.2* Ozonolysis and Hydrogenation of Diacetonides of 24,25- and 25,26-Anhydro-20-hydroxyecdysones. Synthesis of Ponasterone A

Ozonolysis of 2,3:20,22-diacetonides of 24.25-and 25,26-anhydro-20-hydroxyecdysones afforded the corresponding ω-carbonyl derivatives. The hydrogenation of the mentioned dehydration products of 20-hydroxyecdysone acetonide yielded diacetonide of ponasterone A that provided ponasterone A and its 29,22-acetonide at hydrolysis.

Dehydration of LnCl3·6H2O (Ln=Tb, Nd, Dy) in the reaction with i-Bu3Al, Et3Al, Et2AlCl, EtAlCl2 and formation of the complexes LnCl3·3(BuO)3PO

Abstract The dehydration of toluene insoluble salts TbCl 3 ·6H 2 O ( 1 ), DyCl 3 ·6H 2 O ( 2 ) and NdCl 3 ·6H 2 O ( 3 ) in their reaction with organoaluminum compounds (R n AlX 3− n ): i -Bu 3 Al, Et 3 Al, Et 2 AlCl, EtAlCl 2 and the influence of (BuO) 3 PO (TBP) on the process were studied. In the reaction of R n AlX 3− n with the water of crystallization of salts 1 – 3 , aluminoxanes and the following gases are formed: i -BuH for i -Bu 3 Al, EtH for Et 3 Al, EtH and HCl for Et 2 AlCl and EtAlCl 2 as a result of the attack on the AlC or AlCl bond independent of the presence of TBP. In the absence of TBP the salts 1 – 3 are dehydrated by R n AlX 3− n to give insoluble products LnCl 3 ·0.5H 2 O·0.5(R 2 Al) 2 O, where R is alkyl for i -Bu 3 Al and Et 3 Al, or R is alkyl and Cl for Et 2 AlCl. The reaction of R n AlX 3− n with 1 – 3 in the mixture of toluene–TBP at the ratio TBP/Ln≥12:1 results in the complete removal of water from LnCl 3 ·6H 2 O and leads to the formation of homogeneous solutions, containing aluminoxanes and LnCl 3 ·3TBP complexes. Homogeneous solutions, obtained after interaction in the system NdCl 3 ·6H 2 O+TBP+PhMe+R 3 Al were then activated with either i -Bu 3 Al or ( i -Bu 2 Al) 2 O and used as catalysts for polymerization of butadiene. All the catalysts were highly active for polymerization of butadiene, and produced a low-molecular polybutadiene.

Synthesis and transformations of metallacycles 41. Cyclomagnesiation of O-containing 1,2-dienes with Grignard reagents in the presence of Cp2TiCl2

A Cp2TiCl2-catalyzed intermolecular homocyclomagnesiation of O-containing 1,2-dienes and cross-cyclomagnesiation of O-containing 1,2-dienes with aliphatic 1,2-dienes of cyclic and acyclic structure have been accomplished using Grignard reagents, which led to mono- and bicyclic organomagnesium compounds in 61–94% yields.

Homo‐ and methano[60]fullerenes with chiral attached moieties – 1H and 13C NMR chemical shift assignments and diastereotopicity effects

1H and 13C NMR chemical shift predictions of homo‐ and methano[60]fullerenes containing chiral centers in attached fragment were made using the two‐dimensional NMR technique (HH COSY, 1H–13C HSQC and HMBC) and the quantum chemistry GIAO calculation method in the PBE/3ζ approach. The influence of a chiral substituent on the 13C chemical shifts of diastereotopic fullerene carbons was estimated by comparing the calculated and experimental 13C NMR spectra. The resonances of the fullerene carbons in α‐, β‐ and δ‐positions relative to the position of the substituent exhibit the greatest diastereotopic splitting. Copyright