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排序方式: 共有1400条查询结果,搜索用时 31 毫秒
961.
962.
Lagunamides, isolated from a marine cyanobacterium Lyngbya majuscule found in Singapore, showed very potent activities against Plasmodium falciparum and murine leukemia cell line (P388). Herein, a concise synthetic approach toward the total synthesis of a lagunamide B analogue is discussed. Macrolactonization, HWE-olefination, and modified Crimmin’s aldol are some of the key reactions featured in this synthesis. 相似文献
963.
Yahia Lemmouchi Michael C. Perry Allan J. Amass Khirud Chakraborty Etienne Schacht 《Journal of polymer science. Part A, Polymer chemistry》2007,45(17):3975-3985
Biodegradable, amphiphilic, diblock poly(ε‐caprolactone)‐block‐poly(ethylene glycol) (PCL‐b‐PEG), triblock poly(ε‐caprolactone)‐block‐poly(ethylene glycol)‐block‐poly(ε‐caprolactone) (PCL‐b‐PEG‐b‐PCL), and star shaped copolymers were synthesized by ring opening polymerization of ε‐caprolactone in the presence of poly(ethylene glycol) methyl ether or poly(ethylene glycol) or star poly(ethylene glycol) and potassium hexamethyldisilazide as a catalyst. Polymerizations were carried out in toluene at room temperature to yield monomodal polymers of controlled molecular weight. The chemical structure of the copolymers was investigated by 1H and 13C NMR. The formation of block copolymers was confirmed by 13C NMR and DSC investigations. The effects of copolymer composition and molecular structure on the physical properties were investigated by GPC and DSC. For the same PCL chain length, the materials obtained in the case of linear copolymers are viscous whereas in the case of star copolymer solid materials are obtained with low Tg and Tm temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3975–3985, 2007 相似文献
964.
B B Chakraborty 《Proceedings Mathematical Sciences》1990,100(2):185-188
A nearly spherical gas bubble expands adiabatically in a viscous incompressible fluid flowing past it. The Rayleigh-Plesset formula for the growth of the bubble radius is modified due to the flow of the viscous fluid. 相似文献
965.
S Rayaprol Krushna Mavani CM Thaker DS Rana Keka Chakravorty SK Paranjape M Ramanadham Nilesh A Kulkarni DG Kuberkar 《Pramana》2002,58(5-6):877-880
A new series of mixed oxide superconductors with the stoichiometric composition La2−x
Dy
x
Ca
y
Ba2Cu4+y
O
z
(x=0.0 − 0.5, y=2x) has been studied for structural and superconductiong properties. Our earlier studies on La2−x
(Y/Er)
x
Ca
y
Ba2Cu4+y
O
z
series, show a strong dependence of T
c on hole concentration (p
sh). In the present work, the results of the analysis of the neutron diffraction measurements at room temprerature on x=0.3 and 0.5 samples are reported. It is interesting to know that Ca substitutes for both La and Ba site with concomitant
displacement of La onto Ba site. Superconductivity studies show that maximum T
c is obtained for x=0.5, y=1.0 sample (T
c ∼ 75 K), for La1.5Dy0.5Ca1Ba2Cu5O
z
(La-2125). 相似文献
966.
967.
968.
Frederic E. Ziegler Utpal R. Chakraborty Ronald T. Wester 《Tetrahedron letters》1982,23(32):3237-3240
The high diasteroselectivity in the 1,4-addition of dithianylidene anions to α,β-unsaturated ketones is demonstrated to proceed through an alkoxy-Cope rearrangement. 相似文献
969.
Tushar Kanti Chakraborty Pothukanuri Srinivasu Subhasish Tapadar Bajjuri Krishna Mohan 《Journal of Chemical Sciences》2004,116(4):187-207
To meet the growing demands for the development of new molecular entities for discovering new drugs and materials, organic
chemists have started working on many new concepts that can help to assimilate knowledge-based structural diversities more
efficiently than ever before. Emulating the basic principles followed by Nature to build its vast repertoire of biomolecules,
organic chemists are developing many novel multifunctional building blocks and using them to create ‘nature-like’ and yet
unnatural organic molecules. Sugar amino acids constitute an important class of such polyfunctional scaffolds where the carboxyl,
amino and hydroxyl termini provide an excellent opportunity to organic chemists to create structural diversities akin to Nature’s
molecular arsenal. In recent years, sugar amino acids have been used extensively in the area of peptidomimetic studies. Advances
made in the area of combinatorial chemistry can provide the necessary technological support for rapid compilations of sugar
amino acidbased libraries exploiting the diversities of their carbohydrate frameworks and well-developed solid-phase peptide
synthesis methods. This perspective article chronicles some of the recent applications of various sugar amino acids, furan
amino acids, pyrrole amino acids etc. and many other related building blocks in wide-ranging peptidomimetic studies 相似文献
970.
Subenoy Chakraborty 《General Relativity and Gravitation》1997,29(9):1085-1093
In this paper we evaluate the wave function of the universe using the usual Euclidean path integral technique as proposed by Halliwell and Louko for Ashtekar's new variables. Also we consider the new regularization technique developed by Ishikawa and Ueda for evaluation of the path integral. The wave function by solving the Wheeler-DeWitt equation is also presented. 相似文献