Withanolides from Physalis angulata L Okmanov, R. Ya; Makhmudova, M. M.; Bobaev, I. D. ...
Acta crystallographica. Section E, Crystallographic communications,
08/2021, Letnik:
77, Številka:
8
Journal Article
Recenzirano
Odprti dostop
The compounds (17
S
,20
R
,22
R
,24
R
,25
S
)-5β,6β:20,24-diepoxy-4β,25-dihydroxy-1-oxowith-2-en-26,22-olide and (20
R
,22
R
)-5α,14α,20-Trihydroxy-1-oxo-6α,7α-epoxywitha-2-enolide were isolated from ...a chloroform extract of the aerial parts of
Physalis angulata
L. (Solanaceae). Two products were isolated from the chromatographic separation extract. Compound
I
corresponds to physangulide B chloroform monosolvate, C
28
H
38
O
7
·CHCl
3
, while compound
II
is 14α-hydroxyixocarpanolide, C
28
H
40
O
7
. In the two molecular structures, the conformation of the steroid part (rings
A
,
B
,
C
,
D
) does not differ. In both crystals, molecules are linked by intermolecular O—H...O hydrogen bonds along the
c-
axis direction and form a two-dimensional network parallel to the
ac
plane. The absolute configuration was determined from X-ray diffraction data.
The title mol-ecules were synthesized by the reaction of 4-substituted sodium benzoates with chloro-acetic acid amide in the presence of di-methyl-formamide. The yields of 2-amino-2-oxoethyl ...4-bromo-benzoate, C
H
BrNO
,
, 2-amino-2-oxoethyl 4-nitro-benzoate, C
H
N
O
,
, and 2-amino-2-oxoethyl 4-amino-benzoate monohydrate, C
H
N
O
·H
O,
, are 86, 78 and 88%, respectively. The low yield of
is explained by the reduced reactivity of the mol-ecule in a nucleophilic exchange reaction because of the negative induction and negative mesomeric effects of the nitro group on the benzene ring. Single crystals were obtained from the products under the same (temperature and solvent) conditions. In the case of
, the crystals formed as a monohydrate. In all three crystal structures, the same type of inter-molecular N-H⋯O hydrogen bonds are observed, but the mol-ecules differ in some torsion angles as well as in the dihedral angles between the mean planes of the benzene rings and the amide groups.
The main alkaloids such as securinine (
1
), allosecurinine (
2
), and securitinine (
3
) are isolated from the
Securinega suffruticosa
plant and identified by spectral techniques. The spatial ...structure of
3
is determined by single crystal XRD. The inversion of the pyramidal-tetrahedral nitrogen atom of compound
1
in the crystal and the solution is analyzed based on single crystal XRD and NMR spectroscopy data. By the computational methods and NMR spectroscopy it is shown that the configuration of the nitrogen atom in securinine is related to the alkaloid salt formation rather than the crystal field effect (packing factor).
Polymorphs of benzimidazole derivatives Makhmudov, U. S.; Tashkhodjaev, B.; Talipov, S. A. ...
Journal of structural chemistry,
05/2017, Letnik:
58, Številka:
3
Journal Article
Recenzirano
While growing 2-ethylbenzimidazole crystals from methanol, polymorph
1с
is obtained. In polymorphs
1а-с
, 2-ethylbenzimidazole molecules have a different arrangement in the packing and the position ...of the ethyl group relative to the benzimidazole plane. At the same time, the character (sequence) of intermolecular N–H…N bonds is maintained. In polymorph
1b
with four independent molecules, there is an intermolecular Н bond between homonymous molecules. The study of the crystal structure of another benzimidazole derivative (2-(1-hydroxyethyl)benzimidazole (
2
)) reveals a new polymorph. The results of the comparative analysis of the crystal structures of two polymorphs
2а
,
2b
are presented.
The crystal and molecular structures of β-(N-benzoxazoline-2-thione)propionic acid, its monoethanolammonium (NН
2
(CH
2
)
2
OH) and ethylenediammonium (NН
2
(CH
2
)
2
NH
2
) salts are studied. In the ...salts the monoethyleneamine amine group participates in the deprotonation of one ethylenediamine–two β-(N-benzthiazolin-2-one)propionic acid molecules. The geometry of the molecules and intermolecular hydrogen and donor-acceptor bonds in crystals are analyzed. In the crystal structures weak interactions form a two-dimensional layer whose thickness corresponds to unit cell sizes.
The title compound, C16H20N4OS2, was synthesized by the reaction of 2-benzyl-sulfanyl-5-chloro-acetamido-1,3,4-thia-diazole and piperidine in a 1:2 ratio. The planes of the acetamide and ...1,3,4-thia-diazole units are twisted by 10.8 (4)°. The thia-diazole S atom and the acetamide O atom are syn-oriented due to a hypervalent S⋯O inter-action of 2.628 (4) Å. In the crystal, mol-ecules form centrosymmetric dimers via N-H⋯N hydrogen bonds. These dimers are further connected by C-H⋯O inter-actions into (100) layers.
The optimal reactions and beam energies leading to synthesize superheavy elements is searched by studying mass and angular distributions of fission-like products in heavy-ion collisions since the ...evaporation residue cross section consists an ignorable small part of the fusion cross section. The intensity of the yield of fission-like products allows us to estimate the probability of the complete fusion of the interacting nuclei. The overlap of the mass and angular distributions of the fusion-fission and quasifission products causes difficulty at estimation of the correct value of the probability of the compound nucleus formation. A study of the mass and angular distributions of the reaction products is suitable key to understand the interaction mechanism of heavy ion collisions.
A model for describing spontaneous ternary fission of heavy nuclei is presented. It follows from the suggested model that heavy nuclei have the same half-lives in spontaneous ternary and binary ...fission processes. The collinear cluster tripartition process observed in FOBOS experiments is found to be the dominant reaction channel in spontaneous true ternary fission of heavy nuclei within our model. Competition between binary fission and the formation of a trinuclear system, which is responsible for the ratio of spontaneous ternary and binary fission yields, is introduced.
The title compound, 0.759C(19)H(21)ClN(2)O(2)S·0.241C(19)H(21)ClN(2)O(2)S, was synthesized by aryl-sulfonyl-ation of 2-n-butyl-5-chloro-1H-benzimidazole in the presence of triethyl-amine. The crystal ...structure is composed of two mol-ecules, 2-n-butyl-6-chloro-1-(2,4-dimethylphenyl-sulfon-yl)-1H-benzimidazole and 1-(2,4-dimethylphenyl-sulfon-yl)-2-n-butyl-5-chloro-1H-benz-imidazole, in the refined ratio of 0.759 (4):0.241 (4) disordered at the same position in the unit cell. The mol-ecule has three essentially planar fragments viz. benzimidazole, dimethyl-benzene and n-butyl (r.m.s. deviations of 0.009, 0.024 and 0.003 Å, respectively). The angle between the benzimidazole and dimethyl-benzene fragments is 86.0 (1)°. In the crystal, pairs of inter-molecular C-H⋯π inter-actions form centrosymmetrical dimers, which are linked by weak inter-molecular C-H⋯O hydrogen bonds.
A possibility for the formation of three reaction products having comparable masses at the spontaneous fission of
252
Cf is theoretically explored. This work is aimed to study the mechanism leading ...to the observation of the reaction products with masses
M
1
= 136–140 and
M
2
= 68–72 in coincidence with the FOBOS group in JINR. The same type of ternary fission decay has been observed in the
235
U(n
th
, fff) reaction. The potential energy surface (PES) for the ternary system forming a collinear nuclear chain is calculated for a wide range of masses and charge numbers of the constituent nuclei. The results of the PES for the tripartition of
252
Cf(sf, fff) allows us to establish dynamical conditions leading to the formation of fragments with mass combinations of clusters
68−70
Ni with
130−132
Sn and with the missing cluster
48−52
Ca.
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