Orifluoroacetylation and dehydration of 20-hydroxyecdysone acetonides. Synthesis of stachisterone B

Orifluoroacetylation of the 25(OH)-group with subsequent dehydration of the 14(OH)-group takes place in the reaction of 20-hydroxyecdysone 20,22-acetonide and 2,3:20,22-diacetonide with trifluoroacetic anhydride in the presence of pyridine. Dehydration of the 14(OH)-group gives rise to stachisterone B derivatives, which are hydrolyzed to give the phytoecdysteroid stachisterone B.     

1,3-Dimercaptopropyl-2-thiopyrimidines

Reaction of 2-phenyl-1,3-dithiane-5-isothiuronium bromide with halopyrimidines gives 5-pyrimidylthio-1,3-dithianes and 1,3-dimercaptopropyl-2-thiopyrimidines. Some derivatives have been isolated and characterized. The complexing ability of the 1,3-dimercapto-2-thiopyrimidines has been examined by the metallic indicator method.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 5, pp. 605–610, May, 1970.     

N-Trifluoroacetyl-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline ozonides

A three-component condensation of aromatic amine, aldehyde, and cyclopentadiene with subsequent N-trifluoroacetylation leads to 4- and 4,8-substituted N-trifluoroacetyl-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinolines. Ozonation of the double bond in the latter produced the corresponding isomeric stable ozonides having (1R*,4S*,5aR*,6S*,11bR*)-configuration and differing in inversion at the carboxamide nitrogen atom.     

Solidification of castings with easily separable runner

The article formulates a mathematical model of hydrodynamic and thermophysical processes during the solidification of a casting with easily separable runner that makes it possible to determine the optimal dimensions of the feeder channel. It was established by a numerical experiment that the introduction of a separating baffle reduces the intensity of movement of the melt, and considerably reduces the heat exchange between the runner and the body of the casting. The article recommends the optimal dimension of the feeder channel ensuring effective feed to the casting up to its complete solidification.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 20, pp. 103–106, 1989.     

Ozonides with the tetrahydroquinoline and dehydroabietic fragments

Acid-catalyzed three-component condensation of methyl 12-aminodehydroabietate, aromatic aldehydes, and cyclopentadiene gave methyl (4R)-4-aryl-6-isopropyl-10,13a-dimethyl-3a,4,5,8,9,9a,10,11,12,13,13a,13d-dodecahydro-3H-cyclopenta[c]naphtho[1,2-f]quinoline-10-carboxylates and their (4S)-diastereomers. Ozonolysis of the double bond in their N-trifluoroacetyl derivatives synthesized from the (4R)-diastereomers afforded the corresponding ozonides with the (1S,4R,5aS,6R,11aR,12R,15aS,15dR)-configuration.     

Cyclocondensation of methyl 12-aminodehydroabietate with aldehydes and cyclopentadiene. Synthesis of tricyclic diterpenoide fused to tetrahydroquinoline

Three-component cyclocondensation of methyl 12-aminodehydroabietate with cyclopentadiene and formaldehyde or acetaldehyde under acid catalysis afforded polysubstituted naphthoquinoline derivatives with fused oxetanocyclopentane and cyclopentene fragments. Ozonation of the double bond in the N-trifluoroacetyl cyclopentene derivatives gave the corresponding ozonide.     

A comparison of the method of separation of physical variables with the two-field method for modeling the fluid dynamics of casting

We use the example of the two-dimensional problem of siphon filling of a mold by molten metal to compare two methods of studying the flow of a viscous fluid: in vortex-function flow variables (ω, ψ) and in pressurevelocity variables (p, v). The superiority of the (ω, ψ)-method is demonstrated. Two figures. Translated fromTeoreticheskaya i Prikladnaya Mekhanika, No. 25, 1995, pp. 130–132.     

Ab initio investigation of phonon spectra in GdLiF4 compound under hydrostatic pressure

Employing density functional theory (DFT) within the generalized gradient approximation, the GdLiF₄ structure has been studied for a pressure range from 0 to 12 GPa. The influence of pressure on the lattice vibrational spectrum of the scheelite phase (I4₁/a, Z = 4) has been evaluated by means the “direct” approach, i.e., using force constants calculated from atomic displacements. As a result the Raman and infrared modes have been identified and their dependencies on pressure have been investigated and compared with available experimental data. It has been found that instability of the crystal structure appears at pressures above 6 GPa.