A ring-closing metathesis approach to a synthesis of the B ring of eleutherobin

A short and efficient RCM route is reported for the construction of the key nine-membered B ring of eleutherobin starting from the readily available 1,2,5,6-diisopropylidene-d-glucose.     

Synthesis of Pyrimidine Annelated Heterocycles [1]. Regioselective Heterocyclization of 6-Cyclopent-2-enyl-5-hydroxy-1,3-dimethyl-pyrimidine-2,4( 1H, 3H)-dione and 5-Cyclopent-2-enyl-6-hydroxy-1,3-dimethylpyrimidine-2,4( 1H, 3H)-dione

Summary. Two hitherto unreported pyrimidine annelated heterocycles were synthesized from 6-cyclopent-2-enyl-5-hydroxy-1,3-dimethylpyrimidine-2,4(1H,3H)-dione and 5-cyclopent-2-enyl-6-hydroxy-1,3-dimethylpyrimidine-2,4(1H,3H)-dione by reaction with pyridine hydrotribromide or hexamethylenetetramine hydrotribromide. The first one was also obtained by reaction with concentrated sulfuric acid.Received October 28, 2002; accepted October 30, 2002 Published online June 2, 2003     

A comparative investigation of the fatty acid compositions of the seeds of a number of lines of a genetic collection of Gossypium hirsutum

A comparative analysis has been made of the amounts of lipids and their fatty-acid compositions in the seeds of the lines of agenetic collection of cotton plants of the speciesGossypium hirsutum and their hybrids and the variety Tashkent-1. The results obtained on the fatty-acid compositions of some hybrids make it possible to recommend the use of individual lines of cotton plants as donors for improving the food-value indices of cottonseed oil.Institute of Chemsitry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 173–176, March–April, 1991.     

Phase-vanishing methodology for efficient bromination, alkylation, epoxidation, and oxidation reactions of organic substrates

[reaction: see text] In cases where both reactants in a phase-vanishing reaction are less dense than the fluorous phase, an alternative to the U-tube method is to employ a solvent with greater density than the fluorous phase, such as 1,2-dibromoethane. This modification has been successfully applied to the methylation of a phenol derivative with dimethyl sulfate and to the m-CPBA-induced epoxidation of alkenes, N-oxide formation from nitrogen-containing compounds, and S-oxide or sulfone formation from organic sulfides.     

Ethylene spacer-linked bis-acetamidopyridine for dicarboxylic acid recognition and polymeric new wave-like anti-perpendicular arrangement of a host–guest in the solid state

In this paper, 1,2-bis(2-acetamido-6-pyridyl)ethane, receptor 1, having an ethylene spacer is reported to recognise dicarboxylic acids. The binding study in the solution phase is carried out using ¹H NMR (1:1) and UV–vis experiments and in the solid phase by single-crystal X-ray analysis. In ¹H NMR, the downfield shifts of specific amide protons of receptor 1 in 1:1 complexes of receptor and guest diacids, and in the UV–vis experiment, the appearance of an isosbestic point as well as significant binding constants are observed, which thus unambiguously support the complexation of receptor 1 with dicarboxylic acids in solution. Receptor 2, simple 2-acetamido-6-methylpyridine, has lower binding constants than receptor 1 due to cooperative binding of two pyridine amide groups with two acid groups of diacids. In the solid phase, the ditopic receptor 1 shows a grid-like polymeric hydrogen-bonded network that changes to a polymeric wave-like 1:1 anti-perpendicular network instead of the syn–syn polymeric 1:1 (Goswami, S.; Dey, S.; Fun, H.-K.; Anjum, S.; Rahman, A.-U. Tetrahedron Lett. 2005 (a) Goswami, S., Ghosh, K. and Dasgupta, S. 2000. J. Org. Chem., 65: 1907–1914. (b) Goswami, S.; Ghosh, K.; Mukherjee, R. Tetrahedron2001, 57, 4987–4993. (c) Goswami, S.; Ghosh, K.; Halder, M. Tetrahedron Lett.1999, 40, 1735–1738. (d) Goswami, S.; Dey, S.; Fun, H.-K.; Anjum, S.; Rahman, A.-U. Tetrahedron Lett.2005, 46, 7187–7191. (e) Goswami, S.; Jana, S.; Dey, S.; Razak, I.A.; Fun, H.-K. Supramol. Chem.2006, 18, 571–574. (f) Goswami, S.; Jana, S.; Fun, H.-K. Cryst. Eng. Comm.2008, 10, 507–517. (g) Goswami, S.; Jana, S.; Dey, S.; Sen, D.; Fun, H.-K.; Chantrapromma, S. Tetrahedron2008,64, 6426–6433. (h) Goswami, S.; Dey, S.; Jana, S. Tetrahedron2008, 64, 6358–6363 [Google Scholar], 46, 7187–7191), anti–anti polymeric 1:1 (Goswami, S.; Jana, S.; Dey, S.; Razak, I.A.; Fun, H.-K. Supramol. Chem. 2006 (a) Goswami, S., Ghosh, K. and Dasgupta, S. 2000. J. Org. Chem., 65: 1907–1914. (b) Goswami, S.; Ghosh, K.; Mukherjee, R. Tetrahedron2001, 57, 4987–4993. (c) Goswami, S.; Ghosh, K.; Halder, M. Tetrahedron Lett.1999, 40, 1735–1738. (d) Goswami, S.; Dey, S.; Fun, H.-K.; Anjum, S.; Rahman, A.-U. Tetrahedron Lett.2005, 46, 7187–7191. (e) Goswami, S.; Jana, S.; Dey, S.; Razak, I.A.; Fun, H.-K. Supramol. Chem.2006, 18, 571–574. (f) Goswami, S.; Jana, S.; Fun, H.-K. Cryst. Eng. Comm.2008, 10, 507–517. (g) Goswami, S.; Jana, S.; Dey, S.; Sen, D.; Fun, H.-K.; Chantrapromma, S. Tetrahedron2008,64, 6426–6433. (h) Goswami, S.; Dey, S.; Jana, S. Tetrahedron2008, 64, 6358–6363 [Google Scholar], 18, 571–574; Goswami, S.; Jana, S.; Fun, H.-K. Cryst. Eng. Comm. 2008, 10, 507–517; Goswami, S.; Jana, S.; Dey, S.; Sen, D.; Fun, H.-K.; Chantrapromma, S. Tetrahedron 2008, 64, 6426–6433), syn–syn 2:2 (Karle, I.L.; Ranganathan, D.; Haridas, V. J. Am. Chem. Soc. 1997 (a) Garcia-Tellado, F., Goswami, S., Chang, S.K., Geib, S.J. and Hamilton, A.D. 1990. J. Am. Chem. Soc., 112: 7393–7394. (b) Geib, S.J.; Vicent, C.; Fan, E.; Hamilton, A.D. Angew. Chem. Int. Ed. Engl.1993, 32, 119–121. (c) Garcia-Tellado, F.; Geib, S.J.; Goswami, S.; Hamilton, A.D. J. Am. Chem. Soc.1991, 113, 9265–9269. (d) Karle, I.L.; Ranganathan, D.; Haridas, V. J. Am. Chem. Soc.1997, 119, 2777–2783. (e) Moore, G.; Papamicaël, C.; Levacher, V.; Bourguignon, J.; Dupas, G. Tetrahedron2004, 60, 4197–4204. (f) Korendovych, I.V.; Cho, M.; Makhlynets, O.V.; Butler, P.L.; Staples, R.J.; Rybak-Akimova, E.V. J. Org. Chem.2008, 73, 4771–4782. (g) Ghosh, K.; Masanta, G.; Fröhlich, R.; Petsalakis, I.D.; Theodorakopoulos, G. J. Phys. Chem. B2009, 113, 7800–7809 [Google Scholar], 119, 2777–2783) or top–bottom-bound 1:1 (Garcia-Tellado, F.; Goswami, S.; Chang, S.K.; Geib, S.J.; Hamilton, A.D. J. Am. Chem. Soc. 1990 (a) Goswami, S., Ghosh, K. and Dasgupta, S. 2000. J. Org. Chem., 65: 1907–1914. (b) Goswami, S.; Ghosh, K.; Mukherjee, R. Tetrahedron2001, 57, 4987–4993. (c) Goswami, S.; Ghosh, K.; Halder, M. Tetrahedron Lett.1999, 40, 1735–1738. (d) Goswami, S.; Dey, S.; Fun, H.-K.; Anjum, S.; Rahman, A.-U. Tetrahedron Lett.2005, 46, 7187–7191. (e) Goswami, S.; Jana, S.; Dey, S.; Razak, I.A.; Fun, H.-K. Supramol. Chem.2006, 18, 571–574. (f) Goswami, S.; Jana, S.; Fun, H.-K. Cryst. Eng. Comm.2008, 10, 507–517. (g) Goswami, S.; Jana, S.; Dey, S.; Sen, D.; Fun, H.-K.; Chantrapromma, S. Tetrahedron2008,64, 6426–6433. (h) Goswami, S.; Dey, S.; Jana, S. Tetrahedron2008, 64, 6358–6363 [Google Scholar], 112, 7393–7394) co-crystals.

     

Improved Protocol for Thorpe Reaction: Synthesis of 4‐Amino‐1‐arylpyrazole using Solid–Liquid Phase‐Transfer Conditions

Solid–liquid phase‐transfer conditions were employed for the first time in the Thorpe reaction to synthesize 4‐amino‐1‐aryl‐3,5‐substituted‐1H‐pyrazoles 3. Aryl amines were diazotized and coupled with various active methylene compounds such as cyano acetamide, cyanoacetophenone, malononitrile, and ethyl cyanoacetate, resulting into α‐arylhydrazononitriles 1. Cyclization of 1 using α‐bromo ketones or esters resulted in compounds 3.     

高能核碰撞中带电多重数快度与能量和中心度的关系

用强子–弦级联模型JPCIAE及相应的Monte Carlo事例产生器研究相对论性核–核碰撞中带电粒子多重数的赝快度密度对能量和中心度的依赖关系.无需另调任何模型参数的条件下,此模型可以同时较好地描述相对论性pp实验数据及PHOBOS和PHENIX实验组的Au+Au实验数据.本文指出:因〈N_part〉并非严格定义的物理量,致使实验上和理论上确定〈N_part〉有一定任意性,从而使得每参加者核子对的带电粒子赝快度密度随着〈N_part〉的增加可能逐渐增大,也可能逐渐减小,因此用它来区分粒子产生机制是欠妥的.