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Efficient and Facile Synthesis of α-Chloroenones Bearing β-Carbonates or β-Carbamates
Magar, Krishna Bahadur Somai,Lee, Yong Rok Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.12
Efficient synthesis of ${\alpha}$-chloroenones bearing ${\beta}$-carbonates or ${\beta}$-carbamates was achieved by rhodium(II)-catalyzed reaction of cyclic diazodicarbonyl compounds with a variety of chloroformates or carbamyl chlorides in good yields. These reactions provided a useful and rapid route to ${\beta}$-substituted ${\alpha}$-haloenones.
Magar, Til Bahadur Thapa,Seo, Seung Hee,Kadayat, Tara Man,Jo, Hyunji,Shrestha, Aarajana,Bist, Ganesh,Katila, Pramila,Kwon, Youngjoo,Lee, Eung-Seok Elsevier 2018 Bioorganic & medicinal chemistry Vol.26 No.8
<P><B>Abstract</B></P> <P>As part of our effort to develop potential topoisomerase IIα (topo IIα) targeting anticancer agents, we systematically designed a new series of hydroxy and chloro-substituted 2,4-diphenyl 5<I>H</I>-chromeno[4,3-<I>b</I>]pyridines. Total eighteen compounds were synthesized and tested for their ability to inhibit the function of topo I and IIα, and proliferation of human breast (T47D), colorectal (HCT15), and cervix (HeLa) cancer cells. Except compound <B>11</B>, all of the tested compounds displayed selective topo IIα inhibitory activity. Compounds <B>8</B>–<B>18</B>, <B>22</B>, <B>24</B>, and <B>25</B> showed excellent topo IIα inhibitory activity than a positive control, etoposide. Most of the compounds appeared to be superior to reference compounds in their antiproliferative activity. Structure-activity relationship (SAR) study has shown that it is better to place the hydroxyphenyl group at the 4-position of the central pyridine for superior topo IIα inhibition and antiproliferative activity. Similarly, the 3′-, or 4′-hydroxyphenyl substitution at the 2- and 4-positon of pyridine ring is important for better activity than 2′-substitution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new series of hydroxy and chloro-substituted 2,4-diphenyl 5<I>H</I>-chromeno[4,3-<I>b</I>]pyridines were synthesized. </LI> <LI> Evaluated for topo I and IIα inhibitory activity, and antiproliferative activity. </LI> <LI> Compounds showed selective topo IIα inhibitory activity. </LI> <LI> SAR study indicated the importance of hydroxyphenyl-substitution at 4-position. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Organocatalyzed benzannulation for the construction of diverse anthraquinones and tetracenediones
Somai Magar, Krishna Bahadur,Xia, Likai,Lee, Yong Rok The Royal Society of Chemistry 2015 Chemical communications Vol.51 No.41
<P>An efficient one-pot synthesis of anthraquinones and tetracenediones was achieved <I>via</I><SMALL>L</SMALL>-proline catalyzed [4+2] cycloaddition of <I>in situ</I> generated azadiene from α,β-unsaturated aldehydes and 1,4-naphthoquinones or 1,4-anthracenedione in good to excellent yield. This protocol constitutes an unprecedented tandem benzannulation that allows one-pot construction of diverse anthraquinones and tetracenediones in the presence of organocatalysts. This methodology was applied successfully to the synthesis of naturally occurring molecules and photochemically interesting phenanthrenequinone derivatives.</P> <P>Graphic Abstract</P><P>An efficient one-pot synthesis of anthraquinones and tetracenediones was achieved by <SMALL>L</SMALL>-proline catalyzed benzannulation of commercially available 1,4-naphthoquinones or 1,4-anthracenedione with a variety of α,β-unsaturated aldehydes in good to excellent yield. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5cc00623f'> </P>
Widening Women’s Space through Land Rights
Smita Magar 이화여자대학교 아시아여성학센터 2016 이화여자대학교 아시아여성학센터 학술대회자료집 Vol.2016 No.7
How a patriarchal society understands the concept of space seems to determine women’s access to their land rights. This understanding of women space can limit women from realizing their full potentiality as it prevents or discourages them from accessing opportunities that are in public space. In a patriarchal society, women space is mostly within the household, i.e. a private space. While, for men, their space is mostly thought to be of/in public space. The land, in general understanding is a public space. Currently, in Nepal, 60% of women are involved in land; but only about 19% of women have land in their names. The reason for this is due to the discriminatory construction of ‘women space’ in the patriarchal society. Where she belongs? What is she allowed to have as a property? Or through whom she is entitled for the property determines her place and space in the family and the society. This means women are constrained due to the concept of space entitled to them. Along with it, they are exposed to different forms of vulnerabilities and exploitation. So, to empower women, the space where most of them are involved or engaged has to be targeted. The land where they are working, if can legally be made theirs with their full ownership and access, the private space of women will slowly widen to public space. This will eventually lead to breaking the boundaries created by patriarchal societies to limit women participation in public space. With this argument, in this paper, I will focus on how ensuring land rights in agricultural country like Nepal can be a tool for women empowerment, widening their role in the public space and reducing the gender gap. The paper is mainly based on my observation during field research in Nawalparasi district of Nepal. It will also get its ideas supported through different scholars’ arguments and writings.
Thapa Magar, Til Bahadur,Kadayat, Tara Man,Lee, Hwa-Jong,Park, Seojeong,Bist, Ganesh,Shrestha, Aarajana,Kwon, Youngjoo,Lee, Eung-Seok Elsevier 2017 Bioorganic & medicinal chemistry letters Vol.27 No.15
<P><B>Abstract</B></P> <P>A new series of 2-chloropheny-substituted benzofuro[3,2-<I>b</I>]pyridines were designed, synthesized, and evaluated for topoisomerase I and II inhibition and antiproliferative activity. Compounds <B>17</B>–<B>19, 23, 24, 26,</B> and <B>27</B> exhibited excellent topo II inhibitory activity. A systematic structure-activity relationship study revealed the important role of chlorine substitution in the strong topoisomerase inhibitory activity.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Somai Magar, Krishna Bahadur,Lee, Yong Rok American Chemical Society 2013 Organic letters Vol.15 No.17
<P>A sequential Wolff rearrangement of 1-diazonaphthalen-2(1<I>H</I>)-ones followed by trapping of the ketene intermediate with primary and aromatic amines or alcohols and phenols in the presence of various aldehydes generates 1<I>H</I>-indene-3-carboxamides or 1<I>H</I>-indene-3-carboxylates. This constitutes an unprecedented three-component coupling reaction that allows for the synthesis of functionalized indene derivatives under catalyst-free thermal conditions.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orlef7/2013/orlef7.2013.15.issue-17/ol4019908/production/images/medium/ol-2013-019908_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ol4019908'>ACS Electronic Supporting Info</A></P>
Somai Magar, Krishna Bahadur,Edison, T. N. Jebakumar Immanuel,Lee, Yong Rok The Royal Society of Chemistry 2016 Organic & Biomolecular Chemistry Vol.14 No.30
<P>An efficient, facile and regioselective strategy was developed for the construction of diverse 3-anthracenyloxindoles and 3-carbazolyloxindoles via In(OTf)(3)-catalyzed direct arylation reaction of 3-diazooxindoles with anthracenes or carbazoles. This novel methodology involved new C-C bond formation between oxindoles and anthracenes or carbazoles. The fluorescence response of the synthesized compounds to heavy metal ions was also investigated.</P>
Rubin Thapa Magar,송재경 한국미생물·생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.1
Quercetin and its derivatives are important metabolites that belong to the flavonol class of flavonoids. Quercetin and some of the conjugates have been approved by the FDA for human use. They are widely distributed among plants and have various biological activities, such as being anticancer, antiviral, and antioxidant. Hence, the biosynthesis of novel derivatives is an important field of research. Glycosylation and methylation are two important modification strategies that have long been used and have resulted in many novel metabolites that are not present in natural sources. A strategy for modifying quercetin in E. coli by means of glycosylation, for example, involves overexpressing respective glycosyltransferases (GTs) in the host and metabolic engineering for increasing nucleoside diphosphate sugar (NDP-sugar). Still others have used microorganisms other than E. coli, such as Streptomyces sp., for the biotransformation process. The overall study of the structural activity relationship has revealed that modification of some residues in quercetin decreased one activity but increased others. This review summarizes all of the information mentioned above.