排序方式: 共有91条查询结果,搜索用时 15 毫秒
51.
U. Rajasekhar Reddy B. Sreenivasulu D. Satheesh Dhanraj T. S. S. Sundaram G. Srikanth S. Paul Douglas 《合成通讯》2017,47(13):1225-1230
The present work describes the origin, control, and synthesis of two potent impurities of dabigatran etexilate 1, dabigatran dimer 2, and dabigatran n-propyl ester 3 from the commercially available raw materials 2-[(4-cyanophenyl)amino]acetic acid (4) and N-[3-amino-4-(methylamino)benzoyl]-N-2-pyridinyl-β-alanine ethyl ester (5). These impurities are the process-related impurities and may affect the quality of drug substance, during its manufacturing in large scale. These impurities are not only the crucial components in determining the quality and safety of the drug substance 1 but also provide a better understanding of impurity profiling. 相似文献
52.
Mohamed Maher Perseverance Munga Ngoy Aleksandrs Rebriks Cagri Ozcinar Josue Cuevas Rajasekhar Sanagavarapu Gholamreza Anbarjafari 《Entropy (Basel, Switzerland)》2022,24(11)
Boosting the sales of e-commerce services is guaranteed once users find more items matching their interests in a short amount of time. Consequently, recommendation systems have become a crucial part of any successful e-commerce service. Although various recommendation techniques could be used in e-commerce, a considerable amount of attention has been drawn to session-based recommendation systems in recent years. This growing interest is due to security concerns over collecting personalized user behavior data, especially due to recent general data protection regulations. In this work, we present a comprehensive evaluation of the state-of-the-art deep learning approaches used in the session-based recommendation. In session-based recommendation, a recommendation system counts on the sequence of events made by a user within the same session to predict and endorse other items that are more likely to correlate with their preferences. Our extensive experiments investigate baseline techniques (e.g., nearest neighbors and pattern mining algorithms) and deep learning approaches (e.g., recurrent neural networks, graph neural networks, and attention-based networks). Our evaluations show that advanced neural-based models and session-based nearest neighbor algorithms outperform the baseline techniques in most scenarios. However, we found that these models suffer more in the case of long sessions when there exists drift in user interests, and when there are not enough data to correctly model different items during training. Our study suggests that using the hybrid models of different approaches combined with baseline algorithms could lead to substantial results in session-based recommendations based on dataset characteristics. We also discuss the drawbacks of current session-based recommendation algorithms and further open research directions in this field. 相似文献
53.
Panda MK Kaur S Reddy AR Shaikh MM Butcher RJ Gupta V Ghosh P 《Dalton transactions (Cambridge, England : 2003)》2010,39(45):11060-11068
Several titanium isopropoxide complexes [N,N'-bis(2-oxo-3-R(1)-5-R(2)-phenylmethyl)-N,N'-bis(methylene-p-R(3)-C(6)H(4))-ethylenediamine]Ti(O(i)Pr)(2) [R(1) = t-Bu, R(2) = Me, R(3) = H (1b); R(1) = R(2) = t-Bu, R(3) = H, (2b); R(1) = R(2) = Cl, R(3) = H, (3b), R(1) = t-Bu, R(2) = Me, R(3) = Cl (4b); R(1) = R(2) = t-Bu, R(3) = Cl, (5b); R(1) = R(2) = R(3) = Cl, (6b)] supported over sterically demanding aryloxy based [N(2)O(2)]H(2) ligands have been designed as precatalysts for the ethylene polymerization. Specifically, the 1b-6b complexes, when treated with methylaluminoxane (MAO) under 88 ± 0.5 psi of ethylene at 30 °C for 3 h, produced polyethylene polymers of high molecular weight (M(w) = ca. 7.2-8.3 × 10(5) g mol(-1)) having broad molecular weight distribution (PDI = ca. 13.1-14.6). The 1b-6b complexes were conveniently synthesized from the direct reaction of the [N(2)O(2)]H(2) ligands, 1a-6a, with Ti(O(i)Pr)(4) in 69-86% yield. 相似文献
54.
Zinc–Proline Complex: An Efficient,Reusable Catalyst for Direct Nitroaldol Reaction in Aqueous Media
Zinc–proline complex is an effective homogeneous catalyst for the nitroaldol reaction to afford 2‐nitro alcohols in high yields at room temperature in water. The catalyst is reused for several cycles with consistent activity. 相似文献
55.
Mahmood Haj‐Yahya Pushparathinam Gopinath Kolla Rajasekhar Hilda Mirbaha Marc I. Diamond Hilal A. Lashuel 《Angewandte Chemie (International ed. in English)》2020,59(10):4059-4067
The consistent observation of phosphorylated tau in the pathology of Alzheimer's disease has contributed to the emergence of a model where hyperphosphorylation triggers both tau disassociation from microtubules and its subsequent aggregation. Herein, we applied a total chemical synthetic approach to site‐specifically phosphorylate the microtubule binding repeat domain of tau (K18) at single (pS356) or multiple (pS356/pS262 and pS356/pS262/pS258) residues. We show that hyperphosphorylation of K18 inhibits 1) its aggregation in vitro, 2) its seeding activity in cells, 3) its binding to microtubules, and 4) its ability to promote microtubule polymerization. The inhibition increased with increasing the number of phosphorylated sites, with phosphorylation at S262 having the strongest effect. Our results argue against the hyperphosphorylation hypothesis and underscore the importance of revisiting the role of site‐specific hyperphosphorylation in regulating tau functions in health and disease. 相似文献
56.
Venkatapuram Padmavathi Nemallapudi Revathi Chittoor Rajasekhar Chokkappagari Premakumari 《Journal of heterocyclic chemistry》2013,50(3):579-584
A new class of sulfone linked bisheterocycles—pyrrolyl pyrazoles, bispyrazoles, and pyrazolyl isoxazoles—were prepared from 1‐aroyl‐2‐styrylsulfonylethenes, and the products were characterized by spectral parameters and elemental analyses. 相似文献
57.
α-Aminopropargylphosphonates have been synthesized for the first time in good yields and enantiomeric excesses (up to 81% ee) by using a copper(I)-pybox complex as the catalyst. 相似文献
58.
[reaction: see text] N-PMP protected alpha-aminopropargylphosphonates have been synthesized by using a silver(I) triflate-catalyzed one-pot three-component reaction of terminal alkynes, p-anisidine, and diethyl formylphosphonate hydrate. Good to excellent yields of the desired products may be obtained with a very simple procedure. 相似文献
59.
Synthesis and Antimicrobial Activities of Some Triazole,Thiadiazole, and Oxadiazole Substituted Coumarins 下载免费PDF全文
K. Rajasekhar Reddy R. Mamatha M. S. Surendra Babu K. Shiva Kumar K. N. Jayaveera G. Narayanaswamy 《Journal of heterocyclic chemistry》2014,51(1):132-137
Ethyl‐2‐(4‐methyl‐2‐oxo‐2‐coumarin‐7‐yloxy)acetate 1 has been prepared from 7‐hydroxy‐4‐methyl‐2‐coumarin, which on further treatment with hydrazine hydrate in boiling ethanol gave the hydrazide compound 2 . The resulting hydrazide was reacted with substituted aryl isothiocyanates to form thiosemicarbazides compounds 3a , 3b , 3c , 3d , 3e . 1‐(2‐(4‐Methyl‐2‐oxo‐2‐coumarin‐7‐yloxy)acetyl)‐4‐aryl thiosemicarbazides 3 underwent cyclization with different reagents under different reaction conditions to furnish coumarin derivatives possessing triazoles 4a , 4b , 4c , 4d , 4e , thiadiazoles 5a , 5b , 5c , 5d , 5e , and oxadiazoles 6a , 6b , 6c , 6d , 6e , respectively. The structures of all the compounds have been assigned by elemental analysis and spectral studies. The synthesized compounds were screened for their antimicrobial analgesic activities. The nonconventional controlled microwave irradiation synthesis is carried out at (200 W) at 70°C. This approach offers a number of advantages in terms of methodology, high‐product yield, short reaction time, mild reaction conditions, environmentally benign, and easy workup. 相似文献
60.
Sreekanth Tellamekala Mohan Gundluru Santhisudha Sarva Maheshwara Reddy Nadiveedhi Murali Sudileti Rajasekhar Allagadda 《合成通讯》2019,49(4):563-575
A green and efficient synthetic protocol has been developed for the synthesis of a new series of substituted diethyl(((2-methoxy-5-(trifluoromethyl)phenyl)amino)(phenyl)methyl)phosphonates via a one-pot three-component reaction of 2-methoxy-5-trifluoromethyl aniline with various aromatic-substituted aldehydes and diethyl phosphite using meglumine sulfate as an eco-friendly catalyst at room temperature under solvent-free conditions. The merits of this method are high product yield, short reaction time, easy workup, and purification. All the synthesized compounds were evaluated for the antioxidant activity by DPPH, NO, and H2O2 methods using ascorbic acid as a standard. The compounds 4a and 4g showed the highest antioxidant activity than that of the standard ascorbic acid. 相似文献