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21.
D. Umarova S. Kh. Maekh S. Yu. Yunusov P. G. Gorovoi É. V. Boiko 《Chemistry of Natural Compounds》1977,12(6):706-708
Summary The alkaloid composition of four far-eastern species ofThalictrum — Th. amurense, Th. contortum, Th. filamentosum, andTh. minus — have been studied, for the first time in the case of the first three species.Th. amurense contains -allocryptopine and thalictrisine, andTh. contortum contains -allocryptopine. Glaucine and thalicsimidine have been found inTh. filamentosum, and argemonine has been isolated fromTh. minus for the first time.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Pacific Ocean Institute of Bioorganic Chemistry, Far-Eastern Scientific Center of the Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 788–791, November–December, 1976. 相似文献
22.
Stepan S. Basok Gabriele Bocelli Eduard V. Ganin Marina S. Fonari Yurii A. Simonov 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(1):o50-o52
In the title compound, 2C8H18NO3+·2C7H6NO2−·3H2O, proton transfer occurs from the carboxylic acid group of the 4‐aminobenzoic acid (PABA) molecule to the amine group of the macrocycle, resulting in the formation of a salt‐like adduct. The anions are combined into helical chains which are further bound by the water molecules into sheets. The macrocyclic cations are situated between these layers and are bound to the anions both directly and via bridging water molecules. The structure exhibits a diverse system of hydrogen bonding. 相似文献
23.
Yurii N. Panchenko Sergei V. Krasnoshchiokov Philip George Charles W. Bock 《Structural chemistry》1992,3(1):15-26
The results of complete geometry optimizations of the high energy stable gauche,Trans,trans- and gauche,Cis,trans- rotamers of hexa-1,3,5-trienes are reported at the RHF/6-31G//RHF/B-31G level. The angles of rotation around one of the single C-C bonds are found to be 33.7° and 45.5°, respectively. The corresponding harmonic force fields of these molecules are also reported at this level and corrected using scale factors transferred from buta 1,3-diene. Aspecial scale factor was used for the central C=C double bond stretching coordinate to take into account vibronic coupling. The theoretical vibrational frequencies, calculated with the scaled quantum mechanical (SQM) force fields, allow a complete interpretation of the experimental vibrational spectra of these molecules.Preliminary results were reported at the Austin XII Symposium on Molecular Structure, Austin, TX, February 28 through March 3, 1988, S 18, p. 111 (USA) and at the XIXth European Congress on Molecular Spectroscopy, Dresden, September 4 through September 8, 1989, p. 226 (GDR). 相似文献
24.
The crystal structure of [C10N2H10]2[P2Mo5O21(OH)2] · 2H2O, contains the heteropolyanion, [P2Mo5O21(OH)2]4—, together with diprotonated 4, 4′‐bipyridine. The heteropolyanion is built up from five MoO6 octahedra sharing four common edges and one common corner, capped by two PO3(OH) tetrahedra. The structure is stabilized by hydrogen bonds involving the hydrogen atoms of the 4, 4′‐bipyridine, water molecules and the oxygen atoms of the pentamolybdatobisphosphate. This is the first example that this kind of cluster could be isolated in the presence of a poly‐functional aromatic molecule ion. Crystal data: triclinic, P1¯ (No. 2), a = 9.983(2)Å, b = 11.269(2)Å, c = 17.604(4)Å, α = 73.50(3)°, β = 84.07(3)°, γ = 67.96(3)°; V = 1760.0(6)Å3; Z = 2; R1 = 0.037 and wR2 = 0.081, for 9138 reflections [I > 2σ(I)]. 相似文献
25.
The DNA base adenine and four monomethylated adenines were studied in solution at room temperature by femtosecond pump-probe spectroscopy. Transient absorption at visible probe wavelengths was used to directly observe relaxation of the lowest excited singlet state (S(1) state) populated by a UV pump pulse. In H(2)O, transient absorption signals from adenine decay biexponentially with lifetimes of 0.18 +/- 0.03 ps and 8.8 +/- 1.2 ps. In contrast, signals from monomethylated adenines decay monoexponentially. The S(1) lifetimes of 1-, 3-, and 9-methyladenine are similar to one another and are all below 300 fs, while 7-methyladenine has a significantly longer lifetime (tau = 4.23 +/- 0.13 ps). On this basis, the biexponential signal of adenine is assigned to an equilibrium mixture of the 7H- and 9H-amino tautomers. Excited-state absorption (ESA) by 9-methyladenine is 50% stronger than by 7-methyladenine. Assuming that ESA by the corresponding tautomers of adenine is unchanged, we estimate the population of 7H-adenine in H(2)O at room temperature to be 22 +/- 4% (estimated standard deviation). To understand how the environment affects nonradiative decay, we performed the first solvent-dependent study of nucleobase dynamics on the ultrafast time scale. In acetonitrile, both lowest energy tautomers of adenine are present in roughly similar proportions as in water. The lifetimes of the 9-substituted adenines depend somewhat more sensitively on the solvent than those of the 7-substituted adenines. Transient signals for adenine in H(2)O and D(2)O are identical. These solvent effects strongly suggest that excited-state tautomerization is not an important nonradiative decay pathway. Instead, the data are most consistent with electronic energy relaxation due to state crossings between the optically prepared (1)pipi* state and one or more (1)npi* states and the electronic ground state. The pattern of lifetimes measured for the monomethylated adenines suggests a special role for the (1)npi* state associated with the N7 electron lone pair. 相似文献
26.
Hydrothermal investigations in the system MgO/B2O3/P2O5(/H2O) yielded two new magnesium borophosphates, Mg2(H2O)[BP3O9(OH)4] and Mg(H2O)2[B2P2O8(OH)2]·H2O. The crystal structures were solved by means of single crystal X‐ray diffraction. While the acentric crystal structure of Mg2(H2O)[BP3O9(OH)4] (orthorhombic, P212121 (No. 19), a = 709.44(5) pm, b = 859.70(4) pm, c = 1635.1(1) pm, V = 997.3(3) × 106 pm3, Z = 4) contains 1D infinite chains of magnesium coordination octahedra interconnected by a borophosphate tetramer, Mg(H2O)2[B2P2O8(OH)2]·H2O (monoclinic, P21/c (No. 14), a = 776.04(5) pm, b = 1464.26(9) pm, c = 824.10(4) pm, β = 90.25(1)°, V = 936.44(9) × 106 pm3,Z = 4) represents the first layered borophosphate with 63 net topology. The structures are discussed and classified in terms of structural systematics. 相似文献
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30.
Denis S. Baranov Aleksey A. Ryabichev Victor I. Mamatyuk Yurii V. Gatilov Victor G. Kartsev Sergei F. Vasilevsky 《Mendeleev Communications》2012,22(2):114-116
Reaction between 2-alkyl-4-arylbut-3-yn-2-ols and guanidine in refluxing pyridine affords 2-amino-5,5-dialkyl-4-arylmethylidene-2-oxazolines. 相似文献