North Eastern Hill University

About: North Eastern Hill University is a education organization based out in Shillong, Meghalaya, India. It is known for research contribution in the topics: Population & Ruthenium. The organization has 2318 authors who have published 4476 publications receiving 48894 citations.

A facile access to 2-methylthio/alkoxy/amino-3-acylimidazo[1, 2-a]pyridines based on cupric chloride promoted oxidative ring closure of alpha-oxoketene N,S-, N,O-, and N,N-acetals.

Abstract: ion of hydrogen via cation radical intermediate 14 may give resonance stabilized aminyl radical 15 which undergoes facile intramolecular addition to the enamine double bond followed by abstraction of a hydrogen radical or proton to give the final product. Alternatively, electron transfer from nitrogen to Cu(II) ion may take place in the coordination sphere of initially formed copper complex of type 17 to give metal-complexed aminyl radical intermediate 1828 which on subsequent intramolecular cyclization may afford imidazo[1,2-a]pyridines (Scheme 6). Cuprous and cupric salts in the presence of oxygen and pyridine or amines are known to act as useful oxidizing systems for cleavage of hydrazides,29 bishydrazone,30 o-phenylenediamine,31 and for dimerization of aromatic amines.32 We are further exploring the mechanism of this novel oxidative cyclization with CuCl2 and its application for construction of other fused heterocycles. In summary, an efficient method for the synthesis of biologically important 2,3-functionalized imidazo[1,2-a]pyridines has been described via an unprecedented CuCl2-induced oxidative ring closure of novel R-oxoketene N,S-, N,O-, and N,N-acetal intermediates. The methodology allows regiospecific introduction of alkylthio, alkoxy, primary, and secondary amino group in the 2-position of imidazopyridine ring. These functionalities can be further elaborated to construct novel fused heterocyclic ring systems. The other advantages include mild reaction conditions and easy accessibility of N,S-, N,O-, and N,Nacetals, which can be prepared with large structural variations from various aminoheterocycles, thus broadening the scope of this methodology for the synthesis of diverse class of bridgehead nitrogen heterocycles. Experimental Section General. n-Butyllithium (2.5 M in hexane) was purchased from Aldrich Chemical Co. Cu(II)Cl2 (AR grade, moisture free) and BF3‚Et2O were purchased from E-Merck India. Benzene (AR grade) was purchased from Glaxo and used directly. Tetrahydrofuran (THF) was distilled twice over sodium/benzophenone and stored on sodium wire before use. Unless otherwise stated all reagents were purchased from local commercial sources and used without purification. All the R-oxoketene N,S(2a-f) and N,N(3a-d) acetals were prepared according to our reported26 procedure by reacting 2-(lithioamino)pyridine with corresponding R-oxoketenedithioacetals. 1-(4-Methylphenyl)-3,3-bis-(2-pyridylamino)prop-2-en-1one (3b): light yellow crystals; mp 102-103 °C; 1H NMR (400 MHz, CDCl3) δ 2.35 (s, 3H), 6.79-6.82 (m, 1H), 6.88-6.93 (m, 2H), 7.01 (d, 1H, J ) 8.0 Hz), 7.17 (s, 1H), 7.20 (d, 2H, J ) 8.4 Hz), 7.50-7.58 (m, 2H), 7.85 (d, 2H, J ) 8.4 Hz), 8.12-8.13 (m, 1H), 8.38-8.40 (m, 1H), 12.98 (brs, 1H), 14.59 (brs, 1H); 13C NMR (CDCl3) δ 21.0, 80.4, 113.5, 114.8, 117.0, 118.2, 126.6, 128.5, 137.3, 137.6, 138.1, 140.4, 145.4, 148.0, 151.9, 154.1, 155.4, 180.6; IR (KBr) 3450, 1640, 1600, 1585, 1545 cm-1; MS m/z (%) 330 (M+, 56). Anal. Calcd for C20H18N4O: C, 72.71; H, 5.49; N, 16.96. Found: C, 72.96; H, 5.28; N, 16. 85. 1-(4-Chlorophenyl)-3,3-bis-(2-pyridylamino)prop-2-en-1one (3c): yellow crystals; mp 111-112 °C; 1H NMR (400 MHz, CDCl3) δ 6.95-6.98 (m, 1H), 7.01-7.06 (m, 2H), 7.13 (s, 1H), 7.14 (d, 1H, J ) 8.2 Hz), 7.38 (d, 2H, J ) 8.4 Hz), 7.66-7.73 (m, 2H), 7.85 (d, 2H, J ) 8.0 Hz), 8.25 (d, 1H, J ) 4.8 Hz), 8.48 (d, 1H, J ) 4.4 Hz), 13.12 (brs, 1H), 14.54 (brs, 1H); 13C NMR (CDCl3) δ 80.7, 114.3, 115.6, 117.7, 119.0, 128.4, 136.5, 137.9, 138.8, 139.2, 145.9, 148.6, 152.2, 154.6, 156.4, 185.8; IR (KBr) 3400, 1655, 1610, 1580, 1540 cm-1; MS m/z (%) 350 (M+, 60). Anal. Calcd for C19H15ClN4O: C, 65.05; H, 4.31, N, 15.97. Found: C, 65.25; H, 4.21; N, 15.67. General Procedure for the Preparation of N,O-Acetals (4c,d). To a stirred solution of methanolic sodium methoxide (prepared from 0.46 g of Na metal in 15 mL of dry methanol, 15 mmol) was added the respective N,S-acetal (10 mmol) dissolved in 15 mL of dry methanol, and the reaction mixture was stirred at room temperature for 10 min, followed by refluxing for 2 h. It was cooled to room temperature, quenched with saturated NH4Cl solution, and extracted with chloroform. The combined extracts were washed with water, dried (Na2SO4), and evaporated to give the crude N,O-acetals, which were purified by column chromatrography over silica gel using hexane/ethyl acetate (9:1) as eluent. 1-(4-Chlorophenyl)-3-methoxy-3-(2-pyridylamino)prop2-en-1-one (4c): light yellow crystals; mp 137-138 °C; 1H NMR (400 MHz, CDCl3) δ 3.90 (s, 3H), 5.60 (s, 1H), 6.90 (m,1H), 7.40 (d, 2H, J ) 9.0 Hz), 7.50-7.75 (m, 2H), 7.95 (d, 2H, J ) 9.0 Hz), 8.35 (dd, 1H, J ) 6.9, 1.8 Hz), 14.56 (brs, 1H); 13C NMR (CDCl3) δ 46.5, 90.6, 114.5, 118.5, 128.5, 128.6, 137.3, 138.0, 138.4, 146.0, 152.2, 166.6, 184.5; IR (KBr) 3417, 1617, 1589, 1213; MS m/z (%): 288 (M+, 80); Anal. Calcd for C15H13ClN2O2: C, 62.39; H, 4.53; N, 9.70. Found: C, 62.45; H, 4.42; N 9.61. (28) (a) Esker, J. L.; Newcomb, M. Adv. Heterocycl. Chem. 1993, 58, 1. (b) Falles, A. G.; Bniuza, I. M. Tetrahedron 1997, 53, 17543-17594 and references therein. (c) Baslable, J. W.; Hobson, J. D.; Ridell, W. D. J. Chem. Soc., Perkin Trans. 1 1972, 2205. (d) Broka, C. A.; Eng, K. K. J. Org. Chem. 1986, 51, 5043. (29) Tsuji, J.; Nagashima, T.; Qui, N. T.; Takayanagi, H. Tetrahedron 1980, 36, 1311-1315. (30) Tsuji, J.; Takahashi, H.; Kajimoto, T. Tetrahedron Lett. 1973, 4573-4574. (31) (a) Tsuji, J.; Takayanagi, H.; Toshida, Y. Chem. Lett. 1976, 147148. (b) Kajimoto, T.; Takahashi, H.; Tsuji, J. J. Org. Chem. 1976, 41, 1389-1393. (32) (a) Kajimoto, T.; Takahashi, H.; Tsuji, J. Bull. Chem. Soc. Jpn. 1982, 55, 3673. (b) Jackisch, J.; Legler, J.; Kauffmann, T. Chem. Ber. 1982, 115, 659. Scheme 5 Scheme 6 Notes J. Org. Chem., Vol. 65, No. 5, 200

An effective nutrient medium for asymbiotic seed germination and large-scale in vitro regeneration of Dendrobium hookerianum, a threatened orchid of northeast India

Abstract: Background and aims Dendrobium hookerianum is a rare and threatened epiphytic orchid of northeast India. Prospects for conservation would be strengthened by developing an in vitro method for mass propagation. Seeds are minute and difficult to use directly in the field for this purpose, being non-endospermous with a low nutrient content and dependent on a specific fungus for germination and early seedling development. Although produced in large numbers (2–3 million per capsule), <5 % germinate naturally in the wild. Our objective was to develop a rapid and successful method for in vitro propagation based on an initial in vitro asymbiotic seed germination step that achieved high percentages.

Dysregulation of Glucose Metabolism by Oncogenes and Tumor Suppressors in Cancer Cells

Abstract: Cancers are complex diseases having several unique features, commonly described as ‘hallmarks of cancer’. Among them, altered signaling pathways are the common characteristic features that drive cancer progression; this is achieved due to mutations that lead to the activation of growth promoting(s) oncogenes and inactivation of tumor suppressors. As a result of which, cancer cells increase their glycolytic rate by consuming a large amount of glucose, and convert a majority of glucose to lactate even in the presence of oxygen known as the “Warburg effect”. Tumor cells like other cells are strictly dependent on energy for growth and survival; therefore, understanding energy metabolism will give us an idea to develop new effective anti-cancer therapies that target cancer energy production pathways. This review summarizes the roles of tumor suppressors and oncogenes and their products that provide metabolic advantages to cancer cells which in turn leads to the establishment of the “Warburg effect” and ultimately leads to cancer progression. Understanding cancer cell’s vulnerability will provide potential targets for its control.