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151.
Two new ent‐kaurane diterpenes, wedelidins A ( 8 ) and B ( 9 ), together with eighteen other constituents, including the sesquiterpenoids 1 and 2 , ent‐kaurane diterpenes 3 – 7 , triterpenoids 10 and 11 , steroids 12 – 14 , and flavonoids 15 – 17 as well as benzene derivatives 18 – 20 , were isolated from the aerial parts of Wedelia trilobata. The structures of wedelidins A ( 8 ) and B ( 9 ) were elucidated by extensive spectroscopic analyses (including UV, IR, NMR, and MS). Furthermore, the structures of compounds 2 and 3 were confirmed by X‐ray single‐crystal diffraction analyses. 相似文献
152.
Jean Rodolphe Chouna Pepin Alango Nkeng‐Efouet Bruno Ndjakou Lenta Jean Duplex Wansi Beate Neumann Hans‐Georg Stammler Samuel Fon Kimbu Norbert Sewald 《Helvetica chimica acta》2011,94(6):1071-1076
Two new endiandric acid derivatives, beilschmiedic acid F ( 1 ) and beilschmiedic acid G ( 2 ), together with three known constituents, beilschmiedic acid A, beilschmiedic acid C, and sitosterol 3‐β‐D ‐glucopyranoside, were isolated from the stem bark of Beilschmiedia anacardioides. Their structures were elucidated mainly by using a combination of 1D‐ and 2D‐NMR techniques. The structure and relative configuration of beilschmiedic acid G ( 2 ) was also confirmed by X‐ray crystallographic analysis. 相似文献
153.
Michael A. Shestopalov Olga A. Efremova Anton I. Smolentsev Yuri V. Mironov Vladimir E. Fedorov Yong‐Won Song 《Helvetica chimica acta》2011,94(10):1786-1791
A new germanium complex, cis‐[Ge(pyca)2(OH)2]?2 H2O ( 1 ; pyca=pyridine‐2‐carboxylato), was synthesized by the reaction of [Ge(acac)2Cl2] (acac=acetylacetonato=pentane‐2,4‐dionato) with potassium pyridine‐2‐carboxylate (Kpyca) in H2O/THF. According to the single‐crystal X‐ray diffraction analysis, each Ge‐atom of 1 is coordinated by two pyca ligands and two OH? groups (Fig. 1). These molecules are bonded to each other via a system of H‐bonds resulting in a sheet‐like structure (Fig. 2). The complex is decomposed during heating with stepwise mass loss and formation of GeO2 as final product (Fig. 3). 相似文献
154.
Hai‐Qun Gong Quan‐Xiang Wu Lei‐Lei Liu Jun‐Li Yang Rui Wang Yan‐Ping Shi 《Helvetica chimica acta》2011,94(7):1269-1276
Fourteen sesquiterpenoids with an eudesmane C‐atom skeleton, including four new ones, (1β,5α,7β,8β,11β)‐5‐hydroperoxy‐1‐hydroxyeudesm‐4(15)‐eno‐12,8‐lactone ( 1 ), (1β,5α,7β,8β)‐8‐(acetyloxy)‐5‐hydroperoxy‐1‐hydroxycostic acid methyl ester ( 12 ), and a mixture of (1β,3β,4β,7β,8β)‐1,3‐dihydroxyeudesma‐5,11(13)‐dieno‐12,8‐lactone ( 7 ) and (1β,3β,4β,7β,8β,11β)‐1,3‐dihydroxyeudesm‐5‐eno‐12,8‐lactone ( 8 ), were isolated from the aerial parts of Inula japonica (Asteraceae). Their structures were determined by extensive spectroscopic methods, and those of 7 and 12 confirmed by means of single‐crystal X‐ray diffraction analysis. 相似文献
155.
Heating ortho‐nitro‐anilides 1 – 3 and 2‐methyl‐N‐(3‐nitropyridin‐2‐yl)propanamide ( 5 ) with 4 equiv. of a phosphine led to the 2‐substituted benzimidazoles 6 – 8 and to the imidazo[4,5‐b]pyridine 10 , respectively, in yields between 45 and 85%. Heating 1 with (EtO)3P effected cyclisation and N‐ethylation, leading to the 1‐ethylbenzimidazole 6b . The slow cyclisation of the N‐pivaloylnitroaniline 2b allowed isolation of the intermediate phosphine imide 11 that slowly transformed into the 1H‐benzimidazole 7b . The structure of 11 was established by crystal‐structure analysis. While the N‐methylated ortho‐nitroacetanilide 3 cyclised to the 1,2‐dimethyl‐1H‐benzimidazole ( 8 ), the 2‐methylpropananilide 4 was transformed into 1‐methyl‐3‐(1‐methylethyl)‐2H‐benzimidazol‐2‐one ( 9 ). 相似文献
156.
157.
A five-channel (1H, 19F, 31P, 27Al, 13C) 2.5 mm magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) probe is used in combination with three separate receivers for the parallel acquisitions of one (1D) and two-dimensional (2D) NMR spectra in model fluorinated aluminophosphate and porous Al-based metal-organic framework (MOF). Possible combinations to record simultaneously spectra using this set-up are presented, including (i) parallel acquisitions of quantitative 1D NMR spectra of solids containing nuclei with contrasted T1 relaxation rates and (ii) parallel acquisitions of 2D heteronuclear NMR spectra. In solids containing numerous different NMR-accessible nuclei, the number of NMR experiments that have to be acquired to get accurate structural information is high. The strategy we present here, i.e. the multiplication of both the number of irradiation channels in the probe and the number of parallel receivers, offers one possibility to optimize this measurement time. 相似文献
158.
I. V. Ukrainets L. V. Sidorenko O. V. Gorokhova O. V. Shishkin 《Chemistry of Heterocyclic Compounds》2006,42(2):191-196
The reaction of ethyl aminocrotonates with derivatives of malonic acid is a suitable method for the preparation of ethyl 4-hydroxy-6-methyl-2-oxo-1,2-dihydropyridine-5-carboxylates.
One of the synthesized materials has been studied by X-ray crystallography.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, 217–223, February, 2006. 相似文献
159.
Hiroshi Sasaki Atsushi Nakagawa Tomonari Muramatsu Megumi Suganuma Yoriko Sawano Masaki Kojima Keiko Kubota Kenji Takahashi Masaru Tanokura 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2004,80(9):435
Aspergilloglutamic peptidase from Aspergillus niger is a novel pepstatin-insensitive acid endopeptidase distinct from the well-studied aspartic peptidases, and thus is an interesting target for protein structure/function studies. In the present study, we have determined the three-dimensional structure of the enzyme by X-ray crystallography to a 1.4-Å resolution. The results revealed that the enzyme has a unique structure, composed of two seven-stranded anti-parallel β-sheets which form a β-sandwich structure and appear to have a partial two-fold symmetry, suggesting its possible evolution by gene duplication and that the glutamic acid-110 and glutamine-24 in the heavy chain form a catalytic dyad, consistent with our results obtained by site-directed mutagenesis. 相似文献
160.
Mark Botoshansky Menahem Kaftory Brian O. Patrick Keyan Wang 《Tetrahedron letters》2005,46(7):1141-1144
Based on molecular mechanics, Yang photocyclization of α-1-norbornylacetophenone derivatives in the crystalline state was engineered through methylation adjacent to the carbonyl group, thus changing the conformation in the crystal and leading to enhanced diastereo- and enantioselectivity. 相似文献