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991.
Zuhair S. Salih Peter Stegmüller Wolfgang Pfleiderer 《Journal of heterocyclic chemistry》1988,25(5):1443-1447
Acylations of 1,3-dimethyl- ( 1 ) and 1,3,7-trimethylpyrrolo[2,3-d]pyrimidine-2,4-dione ( 2 ) with anhydrides in the presence of trifluoroacetic acid proceed well to give in good yields the corresponding 7-acyl derivatives 3–11 . The 6-trichloroacetyl derivatives 5 and 6 are sensitive towards nucleophiles, which displace the trichloromethyl group easily by formation of the corresponding 6-carboxylic acid derivatives 12–23. The newly synthesized compounds have been characterized by elemental analysis, uv and 1H nmr spectra and pKa, determinations. 相似文献
992.
Summary The kinetics of the reaction of [Cu(TPT)(H2O)3]2+ and [Ni(TPT)(H2O)3]2+ with H2O have been followed and it has been shown that the formation of covalent hydrates is important in the understanding of these systems. The [Co(TPT)(OH)3]– compound and its Ni analogue are attacked by HO– initially to form pseudo-base species and in, the case of Ni , the ligand then hydrolyses to yield a compound related to the carboximate formed when HO– reacts with [Cu(TPT)(OH)3]–. In this reaction too, the formation of a pseudo-base, involving attack of HO– at the triazine ring in the ligand is significant.Part XXI, ref. 2. 相似文献
993.
Prof. Dr. Fritz Sauter Peter Stanetty Hans Potužak Morteza Baradar 《Monatshefte für Chemie / Chemical Monthly》1976,107(3):669-673
The title substances1 and2 were prepared by acylation of the corresponding ethyl 2-amino-thiophene- (or:-4,5,6,7-tetrahydro-benzo[b]thiophene)-3-carboxylates, in some cases followed by reactions introducing a basic substituent.Additionally a group of 2-aroylamino-thiophene-(or:-4,5,6,7-tetrahydro-benzo[b]thiophene)-3-carboxamides was subjected to ring closure reactions, yielding the corresponding 2-aryl-thieno[2,3-d]pyrimidin-4(3H)-ones and 2-aryl-[1]benzothieno[2,3-d]pyrimidin-4(3H)-ones (both:3).
Zum Teil unter Mitarbeit vonFerdinand Fuhrmann 相似文献
Zum Teil unter Mitarbeit vonFerdinand Fuhrmann 相似文献
994.
Wolfgang Oppolzer Roland Achini Emil Pfenninger Hans Peter Weber 《Helvetica chimica acta》1976,59(4):1186-1202
The N-allyl-N-cinnamyl amide 10 undergoes thermal cyclization to a 2:1-mixture of the trans- and cis-benz(f)isoindolines 11a and 12a . By comparison, the thermolysis of the corresponding bis-cinnamylamide 14 proceeds in a highly stereoselective manner to give the cis-fused[4+2]-adduct 16a . Similarly, the trans-fused stereoisomeric adducts 30a and 31a were obtained with high stereochemical control on heating the N-allyl-N-diphenylallyl amide 28 . The thermal transformations 4 → 5 + 6a and 17 → 18a + 20a show the competitive formation of [2+2]-adducts. An alternative approach to (substituted) benz[f]isoindolines 16 via the all-cis-isomer 24a has been developed. The described structures have been assigned on the basis of spectral evidence, chemical correlations and by X-ray-diffraction study of the isomer 16b . These results illustrate the utility of substituent interactions in order to direct intramolecular cyclo-additions at will towards either endo- or exo-products. 相似文献
995.
Hans‐Dietrich Stachel Barbara Zimmer Eduard Eckl Katharina Semmlinger Wolfgang Weigand Ralf Wünsch Peter Mayer 《Helvetica chimica acta》2005,88(6):1208-1220
The 1,2‐dithiolosultam derivative 14 was obtained from the (α‐bromoalkylidene)propenesultam derivative 9 (Scheme 1). Regioselective cleavage of the two ester groups (→ 1b or 2b ) allowed the preparation of derivatives with different substituents at C(3) in the dithiole ring (see 27 and 28 ) as well as at C(6) in the isothiazole ring (see 17 – 21 ; Scheme 2). Curtius rearrangement of the 6‐carbonyl azide 21 in Ac2O afforded the 6‐acetamide 22 , and saponification and decarboxylation of the latter yielded ‘sulfothiolutin’ ( 30 ). Hydride reductions of two of the bicyclic sultams resulted in ring opening of the sultam ring and loss of the sulfonyl group. Thus the reduction of the dithiolosultam derivative 14 yielded the alkylidenethiotetronic acid derivative 33 (tetronic acid=furan‐2,4(3H,4H)‐dione), and the lactam‐sultam derivative 10 gave the alkylidenetetramic acid derivative 35 (tetramic acid=1,5‐dihydro‐4‐hydroxy‐2H‐pyrrol‐2‐one) (Scheme 3). Some of the new compounds ( 14, 22, 26 , and 30 ) exhibited antimycobacterial activity. The oxidative addition of 1 equiv. of [Pt(η2‐C2H4)L2] ( 36a , L=PPh3; 36b , L=1/2 dppf; 36c , L=1/2 (R,R)‐diop) into the S? S bond of 14 led to the cis‐(dithiolato)platinum(II) complexes 37a – c . (dppf=1,1′‐bis(diphenylphosphino)ferrocene; (R,R)‐diop={[(4R,5R)‐2,2‐demithyl‐1,3‐dioxolane‐4,5‐diyl]bis(methylene)}bis[diphenylphosphine]). 相似文献
996.
Targeted mutagenesis and gene knock-out can be mediated by triple helix-forming oligonucleotides (TFO) linked to mutagenic agents, such as psoralen. However, this strategy is limited by the availability of homopurine/ homopyrimidine stretches at or near the target site because such sequences are required for high-affinity triplex formation. To overcome this limitation, we have tested TFO conjugated to psoralen via linker arms of lengths varying from 2 to 86 bonds, thereby designed to deliver the psoralen at varying distances from the third strand binding site present at the 3'end of the supFG1 mutation reporter gene. Following triplex formation and UVA irradiation, mutations were detected using an SV40-based shuttle vector assay in human cells. The frequency and distribution of mutations depended on the length of the linker arm. Precise targeting was observed only for linker arms of length 2 and 6, which also yielded the highest mutation frequencies (3 and 14%, respectively). Psoralen–TFO with longer tethers yielded mutations at multiple sites, with the maximum distance from the triplex site limited by the linker length but with the distribution within that range influenced by the propensity for psoralen intercalation at A:T base-pair-rich sites. Thus, gene modification can be extended beyond the site of third strand binding but with a decrease in the precision of the targeting. 相似文献
997.
We report simulations of laser-driven many-electron dynamics by means of the time-dependent configuration interaction singles (doubles) approach. The method accounts for the correlation of ground and excited states, is capable of describing explicitly time-dependent, nonlinear phenomena, and is systematically improvable. Lithium cyanide serves as a molecular test system in which the charge distribution and hence the dipole moment are shown to be switchable, in a controlled fashion, by (a series of) laser pulses which induce selective, state-to-state electronic transitions. One focus of our time-dependent calculations is the question of how fast the transition from the ionic ground state to a specific excited state that is embedded in a multitude of other states can be made, without creating an electronic wave packet. 相似文献
998.
In the course of searching bioactive natural products from the plant genus Aglaia, we selected two species, A. cordata and A. testicularis, for further chemical study. Totally twenty natural compounds were obtained and structurally elucidated with which eleven of them were discovered for the first time. Among these compounds, lignans, rocaglamides,aglains and bisamides were the main constituents of the two plant species. The results from a bioactive screening indicated that some of the lignans possess potent antibacterial and antifungal activity. 相似文献
999.
van Hooft PA El Oualid F Overkleeft HS van der Marel GA van Boom JH Leeuwenburgh MA 《Organic & biomolecular chemistry》2004,2(9):1395-1403
The scope of a stereoselective three-step approach for the synthesis of sugar derived spiroketals is presented. The methodology consists of Grignard addition of vinyl- or allylmagnesium bromide to a carbohydrate lactone, followed by K-10 clay mediated glycosidation with a terminal alkenol and subsequent ring-closing metathesis of the resulting diene. The generality of this procedure is demonstrated by the synthesis of various pyranose- and furanose-derived spiroketals, as well as more advanced tricyclic spiroketal derivatives. It is shown that functionalisation of the double bond in the resulting spiroketals leads to fused polycyclic ethers. 相似文献
1000.
Venkateshrao S Yin J Jarzecki AA Schultz PG Spiro TG 《Journal of the American Chemical Society》2004,126(50):16361-16367
Resonance Raman (RR) spectra are reported for mesoporphyrin IX bound to the Fab fragment of the ferrochelatase antibody 7G12. Binding induces activation of a Raman band at 680 cm(-1), which is assigned to an out-of-plane porphyrin vibration, gamma15. This is exactly the predicted effect of distorting mesoporphyrin to the geometry of N-methylmesoporphyrin IX, the 7G12 hapten, based on DFT/CIS modeling of the RR spectrum. The modeling also shows that the pyrrole ring that is tilted out of the porphyrin plane bears a nitrogen lone pair, which is therefore available for coordination by an incoming metal ion. The 680 cm(-1) band intensity is approximately 3 times higher for the affinity-matured antibody than for the germline precursor antibody, while intermediate values are found for variants in which germline residues are mutated to mature residues or vice versa. Thus, RR spectroscopy reveals an evolution from weak substrate distortion in the germline antibody to strong substrate distortion in the affinity-matured antibody, and supports the view that catalysis involves a substrate strain mechanism. 相似文献