Development of a method for des-glaucine production in a subcritical water medium

The isomerization of a non-racemic mixture of glaucine isomers to des-glaucine (seco-glaucine) in a subcritical water medium at 200–300°C was conducted with a yield of 53%. The structure of the product was confirmed by NMR spectroscopy and electrospray-ionization mass spectrometry.     

Products of the interaction of veratrole and paraform in a subcritical water medium

The interaction of veratrole and paraform in a subcritical water medium was studied and the macrocyclic compounds (cyclotriveratrylene and cyclotetraveratrylene) were obtained in a ratio of 94: 6. The formation of the aforementioned compounds is confirmed by complex analytical methods, including mass spectrometry with electrospray ionization (ESI MS) and NMR spectroscopy. The data of ESI MS showed that the mixed adducts of the above macrocycles of trimer-cation-tetramer type are formed.     

A Compact Second-Harmonic Generator for Tasks of Precision Spectroscopy Within the Range of 240–600 nm

We develop a universal design of a second-harmonic generator enabling a high-efficiency conversion of the CW laser radiation to a range of 240–600 nm. The distinctive features of the generator are its compact size and high stability achieved using an all-in-one (monolithic) hermetic body frame, which enables applications of this device in a broad range of precision spectroscopy and laser cooling. We design three systems for radiation conversion to ranges of 280, 410, and 560 nm and present their characteristics. The systems are used for laser cooling of magnesium ions (280 nm) and thulium atoms (410 nm). Due to the conversion efficiency and stability, the second-harmonic generators developed surpass most commercially available systems of Western manufacturers.     

Electrospray ionization mass spectrometry of mixtures of triterpene glycosides with <Emphasis Type="Italic">L</Emphasis>-phenylalanine

Electrospray-ionization mass spectrometry (ESI-MS) was used to investigate for the first time the molecular complexation of L-phenylalanine with hederagenin 3-O-α-L-rhamnopyranosyl-(1 → 2)-O-α-L-arabinopyranoside (α-hederin) and its 28-O-α-L-rhamnopyranosyl-(1 → 4)-O-β-D-glucopyranosyl-(1 → 6)-O-β-D-glucopyranosyl ester (hederasaponin C). The glycoside/L-phenylalanine complexes with a 1:1 molar ratio turned out to be most stable. The structures of the glycosides and L-phenylalanine have been concluded to have an impact on the complexation process.     

Synthesis of Phenanthrene Alkaloids from Herbal Aporphine Alkaloids in Subcritical Water Using Synthesis of Seco-Glaucine as an Example

Transformation of the model aporphine alkaloid glaucine into the phenanthrene alkaloid secoglaucine (seco-GL) in subcritical water at 100–250°C without catalytic additives is studied. The maximum yield of seco-glaucine is achieved at 250°C. It is shown that under these conditions the load of the initial compound affects only slightly the yield of the target compound, which is on average 80%. The increase of the GL load up to 400 mg results in precipitation of the target seco-GL directly from the reaction mixture. The suggested method avoids the use of costly and toxic organic solvents.     

Molecular structure of Hf(BH4)4 investigated by quantum mechanical calculations and gas-phase electron diffraction

The structure of the gaseous hafnium tetrakis(tetrahydroborate) molecule, Hf(BH4)4, has been investigated by detailed quantum mechanical calculations and by analysis of its gas electron-diffraction (GED) pattern. The ground-state geometry possesses T symmetry with all of the triply-bridged BH4 groups twisted equally about the Hf...B-H axes. Salient structural parameters (ra distances, r angles) deduced from the GED pattern by the SARACEN method were: r(Hf...B) 231.4(2), r(Hf-Hb) 221.5(7), r(B-Hb) 127.6(5), r(B-Ht) 121(1) pm, Hf...B-Hb 69.4(3), Hb-B-Hb 108.4(4), Hb-B-Ht 110.6(3), B...Hf...B-Hb 166(1) degrees. A notable feature is the large magnitude of the Hf...B and Hf-Hb anharmonicity parameters, attributed to the fluxional hydrogen atom exchange process. The properties are compared with those of related tetrahydroborates..     

Joys and pitfalls of fermi surface mapping in Bi(2)Sr(2)CaCu(2)O(8+delta) using angle resolved photoemission

On the basis of angle-scanned photoemission data recorded using unpolarized radiation, with high (E,k) resolution, and an extremely dense sampling of k space, we resolve the current controversy regarding the normal state Fermi surface (FS) in Bi(2)Sr(2)CaCu(2)O(8+delta). The true picture is simple, self-consistent, and robust: the FS is holelike, with the form of rounded tubes centered on the corners of the Brillouin zone. Two further types of features are also clearly observed: shadow FSs, which are most likely to be due to short range antiferromagnetic spin correlations, and diffraction replicas of the main FS caused by passage of the photoelectrons through the modulated Bi-O planes.     

On locally convex hypersurfaces in Hadamard manifolds

Locally convex compact hypersurfaces immersed in a hollow simply connected Riemannian space of nonpositive sectional curvature are considered. They are proved to be convex hypersurfaces homeomorphic to the sphere. A similar result for immersed hypersurfaces with nonpositive definite second quadratic form of rank no smaller than one is obtained. Translated fromMatematicheskie Zametki, Vol. 67, No. 4, pp. 498–507, April, 2000.