排序方式: 共有27条查询结果,搜索用时 15 毫秒
1.
M Suguna LakshmiB.S.R Reddy 《European Polymer Journal》2002,38(4):795-801
New epoxide and cyanate ester resins with an aromatic ester backbone namely 1,3-[di-(4-glycidyloxy diphenyl-2,2′-propane)]-isophthalate (DGDPI) and 1,4-[di-(4-cyanato diphenyl-2,2′-propane)]-terephthalate (DCDPT) were synthesized and the intermediates were characterized by IR, 1H-/13C-NMR spectroscopic methods. The cured products from DGDPI and DHDPI exhibited higher Tg compared with standard epoxy system. The increase in the Tg may be due to the cyanate ester and rigid aromatic backbones present in the curing system. 相似文献
2.
Reddy PG Chun BK Zhang HR Rachakonda S Ross BS Sofia MJ 《The Journal of organic chemistry》2011,76(10):3782-3790
PSI-352938 is a novel 2'-deoxy-2'-α-fluoro-2'-β-C-methyl 3',5'-cyclic phosphate nucleotide prodrug currently under investigation for the treatment of hepatitis C virus (HCV) infection. PSI-352938 demonstrated superior characteristics in vitro that include broad genotype coverage, superior resistance profile, and high levels of active triphosphate in vivo in the liver compared to our first and second generation nucleoside inhibitors of this class. Consequently, PSI-352938 was selected for further development and an efficient and scalable synthesis was sought to support clinical development. We report an improved, diastereoselective synthesis of a key 1'-β-nucleoside intermediate 13 via S(N)2 displacement of 1-α-bromo ribofuranose sugar 16 with the potassium salt of 6-chloro-2-amino purine and an efficient method to prepare cis-Rp cyclic phosphate (PSI-352938) in a highly stereoselective manner without any chromatographic purification. The 1-α-bromo sugar 16 was stereospecifically prepared from the corresponding 1-β-lactol in high yield under mild bromination conditions using CBr(4)/PPh(3) (Appel reaction). The desired cis-Rp 3',5'-cyclic phosphate construction was accomplished using isopropyl phosphorodichloridate readily obtained from POCl(3) and isopropyl alcohol. The base combination of Et(3)N/NMI was identified as a key factor for producing PSI-352938 as the major (>95%) diastereomer (cis-Rp) in high yield after the final cyclization step. The current route described in this article was successfully used to produce PSI-352938 on multikilogram scale. 相似文献
3.
R. Krishna Mohan Rao Kallury E. V. Suguna Bhushana Rao 《Journal of mass spectrometry : JMS》1977,12(8):536-538
2,4-Dihydroxybenzophenone Oxime is found to undergo loss of OH·, H2O, NHOH·; and PhCNO when subjected to electron impact, revealing novel hydrogen and skeletal migrations. The fragmentation mechanisms are found to differ considerably from those of benzophenone oxime and we confirmed these cleavages by exact mass measurements and deuterium labelling. 相似文献
4.
In this paper, we give the necessary and sufficient conditions for a linear transformation of a mean-starshaped sequence to be positive. Using this result, we obtain the necessary and sufficient conditions for a lower triangular matrix to preserve the mean-starshape of a sequence and we discuss some special cases of linear transformations. Our next result deals with the convergence of a sequence of mean-starshaped sequences to any given mean-starshaped sequence and the positivity of a linear operator on the set of mean-starshaped sequences. 相似文献
5.
Muralidhar Yegireddy Prakash Nadoor Suguna Rao Pavithra Balekatte Hanumanthu Rashmi Rajashekaraiah Santhosh Chickankandahalli Ramachandrappa Girish Mallikarjun Halemani Sravanthi Mannem Tollamadugu Naga Venkata Krishna Vara Prasad Sunilchandra Ubaradka 《Molecules (Basel, Switzerland)》2022,27(21)
Meloxicam (MLX) is currently used in the therapeutic management of both acute and chronic inflammatory disorders such as pain, injuries, osteoarthritis, and rheumatoid arthritis in both humans and animals. Gastrointestinal toxicity and occasional renal toxicity were observed in patients taking it for a long-term period. Meloxicam’s late attainment of peak plasma concentration results in a slow onset of action. The goal of the current study was to prepare and characterize chitosan encapsulated meloxicam nanoparticles (CEMNPs) with high bioavailability and less gastro intestinal toxicity in order to prevent such issues. The size of the prepared CEMNPs was approximately 110–220 nm with a zetapotential of +39.9 mV and polydispersity index of 0.268, suggesting that they were uniformly dispersed nanoparticles. The FTIR and UV-Vis spectroscopy have confirmed the presence of MLX in the prepared CEMNPs. The pharmacokinetics have been studied with three groups of male Wistar rats receiving either of the treatments, viz., 4 mg·kg−1 of MLX and 1 or 4 mg·kg−1 of CEMNPs. Plasma samples were collected until 48 h post administration, and concentrations of MLX were quantified by using reverse (C18) phase HPLC. Non-compartmental analysis was applied to determine pharmacokinetic variables. Upon oral administration, the maximum concentration (Cmax) was reached in 4 h for CEMNPs and 6 h for MLX. The mean area under the plasma MLX concentration-time curve from ‘zero’ to infinity (AUC0–∞), half-life (t1/2β), and mean resident time (MRT) of 1 mg·kg−1 of CEMNPs was 1.4-, 2-, and 1.8-fold greater than 4 mg·kg−1 of MLX. The prepared CEMNPs demonstrated quicker absorption and prolonged release along with a significant improvement in the bioavailability of MLX, paving a prospective path for the development of drugs with enhanced bioavailability with less side effects. 相似文献
6.
T. R. Govindachari K. Nagarajan S. Rajeswari H. Suguna B. R. Pai 《Helvetica chimica acta》1977,60(7):2138-2150
Debenzylation of 1-(3-benzyloxybenzyl)-1,2,3,4-tetrahydroisoquinolines 1 , 6 , 7 with hydrochloric acid and ethanol gave the corresponding phenolic isoquinolines 2 , 8 , 9 and tetrahydroprotoberberines 4 , 12 , 13 . Compounds 2 , 8 , 9 on photolysis also gave, besides the expected noraporphines 3 , 10 , 11 , the tetrahydroprotoberberines 4 , 12 , 13 [1–4] (Schemes 1 and 2). 6-Benzyloxy-1-(5-benzyloxy-2-bromo-benzyl)-1,2,3,4-tetrahydroisoquinoline (27a) containing no methoxy or methylenedioxy groups either in ring A or C does not give protoberberine during debenzylation; but 28 , the debenzylation product of 27a , on photolysis gives both the noraporphine 29 and the tetrahydroprotoberberine 30 (Scheme 6), proving that during debenzylation of 1-(3-benzyloxybenzyl)-1,2,3,4-tetrahydroisoquinolines containing additional methoxy or methylenedioxy groups, the necessary formaldehyde comes from the latter groups. During photolysis both the methoxy groups (methylenedioxy groups) and the C(3) atom of the tetrahydroisoquinoline moiety provide the formaldehyde. Veratrole under debenzylation and photolytic conditions and tetrahydroisoquinoline under the latter condition also give rise to formaldehyde (Schemes 8 and 10). The novel bromohomoprotoberberine 43 along with 42 was formed during debenzylation of the 1-phenethyl-1,2,3,4-tetrahydroisoquinoline 41 . Photolysis of 42 yielded the novel nor-homoaporphine 44 , in addition to 43 ; the latter was debrominated to give the homoberbine 45 . 相似文献
7.
Adhish Jaiswal Raja Das Suguna Adyanthaya Pankaj Poddar 《Journal of nanoparticle research》2011,13(3):1019-1027
Here we report for the first time, a detailed synthesis mechanism of GdCrO3 nanoparticles using a surfactant-less hydrothermal method. We also report a detailed study of their structural and optical properties. The selected area electron diffraction and powder X-ray diffraction studies of GdCrO3 nanoparticles show pure phase and excellent crystallinity with average particle size around 50–60 nm. The structural analysis indicates a distorted perovskite crystal structure with lattice parameter values of a = 5.3099 ± 0.0022, b = 5.51793 ± 0.00226, and c = 7.60426 ± 0.00315 Å. For the first time, we report the room temperature UV–vis, photoluminescence, FTIR, and X-ray photoelectron spectroscopy results and their detailed analysis for GdCrO3. These results provide optical signatures of the formation of GdCrO3 where both Gd3+ and Cr3+ play dominant role in different frequency regions. 相似文献
8.
Ross BS Reddy PG Zhang HR Rachakonda S Sofia MJ 《The Journal of organic chemistry》2011,76(20):8311-8319
Prodrugs of therapeutic nucleoside monophosphates masked as phosphoramidate derivatives have become an increasingly important class of antiviral drugs in pharmaceutical research for delivering nucleotides in vitro and in vivo. Conventionally, phosphoramidate derivatives are prepared as a mixture of two diastereomers. We report a class of stable phosphoramidating reagents containing an amino acid ester and two phenolic groups, one unsubstituted and the other with electron-withdrawing substituents. The reagents can be isolated as single diastereomers and reacted with the 5'-hydroxyl group of nucleosides through selective nucleophilic displacement of the substituted phenol to prepare single diastereomer phosphoramidate products. This method has been used to prepare the HCV clinical candidate PSI-7977 in high yield and high diastereomeric purity. 相似文献
9.
In a magnon-phonon interaction an energy minimum is obtained in the one-magnon ground-state dispersion. The magnon momentum at the minimum is half the product of the mass of the magnon and the sound velocity, . 相似文献
10.
Anita Swami Amol Jadhav Ashavani Kumar Suguna D. Adyanthaya Murali Sastry 《Journal of Chemical Sciences》2003,115(5-6):679-687
This paper describes the formation of water-dispersible gold nano-particles capped with a bilayer of sodium dodecylsulphate
(SDS) and octadecylamine (ODA) molecules. Vigorous shaking of abiphasic mixture consisting of ODA-capped gold nanoparticles
in chloroform and SDS in water results in the rapid phase transfer of ODA-capped gold nanoparticles from the organic to the
aqueous phase, the latter acquiring a pink, foam-like appearance in the process. Drying of the coloured aqueous phase results
in the formation of a highly stable, reddish powder of gold nanoparticles that may be readily redispersed in water. The water-dispersible
gold nanoparticles have been investigated by UV-Vis spectroscopy, differential scanning calorimetry (DSC), thermogravimetric
analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). These studies indicate the presence of interdigitated
bilayers consisting of an ODA primary monolayer directly coordinated to the gold nanoparticle surface and a secondary monolayer
of SDS, this secondary monolayer providing sufficient hydrophilicity to facilitate gold nanoparticle transfer into water and
rendering them water-dispersible.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献