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排序方式: 共有497条查询结果,搜索用时 15 毫秒
1.
2.
J.S. Yadav B.V. Subba Reddy V. Sunitha K. Srinivasa Reddy K.V.S. Ramakrishna 《Tetrahedron letters》2004,45(42):7947-7950
Aryl amines react with endocyclic ene-carbamates such as tert-butyl 2,3-dihydro-1H-1-pyrrolecarboxylate and tert-butyl 1,2,3,4-tetrahydro-1-pyridinecarboxylate, on the surface of montmorillonite KSF clay under mild conditions to afford the corresponding 3-aminopropylhexahydropyrrolo[3,2-c]quinoline or 4-aminobutyloctahydrobenzo[h][1,6]naphthyridine derivatives in excellent yields with moderate diastereoselectivity. 相似文献
3.
Bradford P. Mundy Ramanuajan Srinivasa Rodney D. Otzenberger A.Richard DeBernardis 《Tetrahedron letters》1979,20(29):2673-2676
The formation of the initial carbonium ion in the pinacol rearrangement will be the major factor in determining product composition when the reaction is carried out at 0°C with concentrated sulfuric acid. 相似文献
4.
A mild and highly efficient deoxygenation of variety of N-oxides using an inexpensive CuX, or a CuX-Zn or CuX-Al couple is described. 相似文献
5.
Marimganti S Yasmeen S Fischer D Maier ME 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6687-6700
The synthesis of the omega-amino acid 4 is described utilizing a two-dimensional synthesis strategy combined with an enzymatic differentiation of homotopic ester groups. The amino acid 4 features two non-bonded interactions that result in conformational constraints on a cyclic construct. This amino acid was incorporated into the four macrolactams 17, 22, 31, and 37. The ring in 17 and 22 is 18-membered, whereas 31 and 37 have a 19-membered ring. The pairs with the same ring size differ in a N-methyl group. For the larger macrolactams (31 and 37) conformational analysis showed that the macrocyclic rings are somewhat more rigid than in the natural lead, the depsipeptide jasplakinolide. Nevertheless, their conformations are comparable to the natural product. There are no intramolecular hydrogen bonds, neither is the cis-rotamer populated in the N-methyl compound 37. Due to the increased flexibility of the smaller macrolactams 17 and 22 and signal overlap, a distinct solution structure could not be obtained for these compounds. The amino acid 4 should be useful for restricting the conformation of other small peptides. 相似文献
6.
Landa Purushottam Unnikrishnan V. B. Dattatraya Gautam Rawale Mansi Gujrati Surya Dev Mishra Sajeev T. K. Neelesh C. Reddy Srinivasa Rao Adusumalli Ram Kumar Mishra Vishal Rai 《Chemical science》2020,11(48):13137
Analytically pure proteins are indispensable for diverse applications, including therapeutics. Here, we report a methodology where a single amino acid, glycine, enables metal-free protein purification. This robust platform is enabled by a Gly-tag resin for site-specific capture, enrichment, and release through chemically triggered C–C bond dissociation by resonance-assisted electron density polarization.Gly-tag resin precisely captures and releases a protein with one glycine at the N-terminus. The user-friendly protocol delivers analytically pure protein free of metal contaminants. 相似文献
7.
Maciej Adamczyk Srinivasa Rao AkireddyPhillip G Mattingly Rajarathnam E Reddy 《Tetrahedron》2003,59(30):5749-5761
A total of 11 novel phosphoramidites, 3a-d, 4a-d and 14a-c were prepared from 2′-deoxyuridine functionalized at 5 and 6-position of the pyrimidine ring with hapten reporter groups, e.g. adamantane, carbazole, dansyl and dabsyl, suitable for use in immunodetection nucleic acid testing assays. 相似文献
8.
Anionic wormlike micellar fluids that display cloud points: rheology and phase behavior 总被引:1,自引:0,他引:1
We report our investigations into the self-assembly of sodium oleate (NaOA) in the presence of a binding salt (triethylammonium chloride, Et(3)NHCl) simple salt (potassium chloride, KCl). Both salts promote the growth of long, wormlike micelles in NaOA solutions, thereby increasing the fluid viscosity. The significant difference with the Et(3)NHCl salt is that it also modifies the phase behavior of NaOA solutions. Specifically, NaOA/Et(3)NHCl solutions display cloud points upon heating, followed by phase separation into two liquid phases. Such cloud point behavior is rarely observed in ionic surfactant systems, although it is common in nonionic surfactant solutions. Interestingly, while cloud points are not observed with KCl, the addition of KCl to NaOA/Et(3)NHCl solutions further lowers the cloud point temperature. Also, in the case of tetraethylammonium halide salt, neither a cloud point nor an increase in viscosity is observed. The clouding in the case of Et(3)NHCl is attributed to the temperature-induced aggregation of anionic micelles whose surface is covered by bound counterions. 相似文献
9.
K. Nagaiah D. Sreenu R. Srinivasa Rao G. Vashishta J.S. Yadav 《Tetrahedron letters》2006,47(26):4409-4413
trans-Fused pyrano- and furanotetrahydroquinoline derivatives have been synthesized via a one-pot three-component aza-Diels-Alder reaction of aryl imines formed in situ from aromatic amines and arylaldehydes with cyclic enol ethers,such as 3,4-dihydro-2H-pyran and 2,3-dihydrofuran,in the presence of 1 mol % of phosphomolybdic acid under solvent-free conditions at room temperature in good to excellent yields. 相似文献
10.
Srinivasa Rao Dasari Subbaiah Tondepu Lakshmana Rao Vadali Nareshvarma Seelam 《合成通讯》2020,50(19):2950-2961
Abstract Polyethylene glycol-400 (PEG-400) has been developed as an efficient and eco-friendly reaction medium for the synthesis of new isoxazolyl pyrido[2,3-d]pyrimidine derivatives 11 from isoxazolyl cyanoacetamide synthon 7. Compound 7 was employed with various aromatic aldehydes 8 and malononitrile 9 in the presence of triethylamine (Et3N) to afford the corresponding (E)-6-amino-1-(3-methyl-5-styrylisoxazol-4-yl)-2-oxo-4-phenyl-1,2-dihydro- pyridine-3,5-dicarbonitrile 10 at room temperature by using PEG-400 as a solvent medium as well as catalyst. The intermediate 10 on treatment with thiourea in the presence of PEG-400 at 90?°C to give the target compounds isoxazolyl pyrido[2,3-d]pyrimidines 11 in good to excellent yields. The newly synthesized compounds 10 and 11 were characterized by IR, 1H NMR, 13C NMR, and HRMS analysis. The target compounds 11a-x was screened for their anti-inflammatory and analgesic activities. Among the tested compounds, the compounds 11s, 11t, 11u, 11v, 11w, and 11x showed significant anti-inflammatory and potent analgesic activities as that of reference drugs. The advantages of this protocol are operational simplicity, catalyst free, environmental safety, wide substrate scope, good yields, and PEG-400 can be recovered and reused. Most significant of all, this protocol is green. 相似文献