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Asymmetric Synthesis of 2′-<i>C</i>-Methyl-4′-selenonucleosides as Anti-Hepatitis C Virus Agents
Lee, Hyejin,Jarhad, Dnyandev B.,Yu, Jinha,Lee, Choongho,Jeong, Lak Shin American Chemical Society etc. 2019 Journal of organic chemistry Vol.84 No.22
<P>In search of a new template for anti-hepatitis C virus (HCV) agents, we designed and synthesized the 2′-<I>C</I>-methyl-4′-selenopyrimidine and -purine nucleosides and their phosphoramidate prodrugs to replace a furanose oxygen of anti-HCV nucleos(t)ides with a selenium atom on the basis that selenium is a chemical isostere of oxygen. These nucleosides are expected to show different physicochemical properties such as better lipophilicity which might enhance the penetration across cell membranes and the conformational constraint induced by a bulky selenium atom in the sugar ring. The 2′-<I>C</I>-methyl-4′-selenopyrimidine and -purine nucleosides <B>8</B> and <B>9</B> were synthesized from 2-<I>C</I>-methyl-<SMALL>D</SMALL>-ribono-γ-lactone (<B>14</B>) via construction of 2-<I>C</I>-methyl-<SMALL>D</SMALL>-selenosugar <B>18</B> through <I>C</I>-4 epimerization and S<SUB>N</SUB>2 cyclization with Se<SUP>2-</SUP> as key steps. The key 4′-selenosugar was converted to the 2′-<I>C</I>-methyl-4′-selenopyrimidine and -purine nucleosides using Pummerer-type rearrangement and Vorbrüggen glycosylation, respectively. In addition, the ProTide strategy has been applied to synthesize the adenine and uracil phosphoramidate derivatives <B>10a</B> and <B>10b</B> to overcome the limitations associated with parent nucleosides such as inefficient conversion to their corresponding 5′-monophosphate form and poor cellular uptake. The regio- and stereochemistry of 4′-selenonucleosides were confirmed by 2D NOESY NMR spectroscopy and X-ray crystallography. None of the final pyrimidine and purine nucleosides and their prodrugs exhibited significant anti-HCV activity up to 100 μM.</P> [FIG OMISSION]</BR>
A Study on the Application of Safeguards to Small Modular Reactor
Jinha Choi,Hyun-Jo Kim,Byung-Doo Lee,Sung-Ho Lee,Juang Jung 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
In addition to Korea, various countries such as the United States, the United Kingdom, France, and China are designing small module-type reactors. In particular, a small modular reactor is the power of 300 MWe or less, in which the main equipment constituting the nuclear reactor is integrated into a single container. Depending on the purpose, small modular reactors are being developed to help daily life such as power, heating supply, and seawater desalination, or for power supply such as icebreakers, nuclear submarines, and spacecraft propellants. Small modular reactors are classified according to form. It can be classified into light-water reactors/ pressurized light-water reactors based on technology proven in commercial reactors, and non-lightwater reactors based on fuel and coolant type such as Sodium-cooled Fast Reactor, High temperature gas-cooled reactor, Very high temperature reactor and Moltenn salt reactor. SMRs, which are designed for various purposes, have the biggest difference from commercial nuclear reactors. The size of SMRs is as small as 1/5 of that of the commercial reactors. Several modules may be installed to generate the same power as commercial reactors. Because of the individually operation for each module, load follow is possible. Also, The reactor can be cooled by natural convection because the size is small enough. It is manufactured as a module, the construction period can be reduced. Depending on the characteristics of these SMRs, application for safeguards is considered. There are many things to consider in terms of safeguards. Therefore, it is IAEA inspection or other approaches for SMRs installed and remotely operated in isolated areas, data integrity for remote monitoring equipment to prevent the diversion of nuclear materials, verification method and material accountancy and control for new fuel types and reactors. Since SMR is more compact and technical intensive, safeguards should be considered at the design stage so that safeguards can be efficiently and effectively implemented, which is called the Safeguards by design (SBD) in the IAEA. In this paper, according to the characteristics of SMR, we will analyze the advantages/disadvantages from the point of view of safeguards and explain what should be considered.
초음파 테이블을 이용한 단결정 사파이어 웨이퍼의 ELID 연삭가공 특성 연구
황진하(JinHa Hwang),곽태수(Tae-Soo Kwak),이득우(Deug-Woo Lee),정명원(Myung-Won Jung),이상민(Sang-Min Lee) 한국기계가공학회 2013 한국기계가공학회지 Vol.12 No.4
Single crystal sapphire being used in high technology industry is a brittle material with a high hardness and excellent physical properties. ELID(Electrolytic In-Process Dressing) grinding technology was applied to material removal machining process of single crystal sapphire wafer. Ultrasonic vibration which added to material using ultrasonic table was adopted to efficient ELID grinding of sapphire materials. The evaluation of the ground surface of single crystal sapphire wafer was carried out by means of surface measuring by using AFM(Atomic Force Microscope), surface roughness tester and optical microscope device. As the results of experiment, it was shown that more efficient grinding was conducted when using ultrasonic table. In case of using #170 grinding wheel, surface roughness of ELID ground specimen in using ultrasonic table was superior to ELID ground specimen without ultrasonic table. However, In case of using #2000 grinding wheel, surface roughness of ELID ground specimen in using ultrasonic table was inferior to ELID ground specimen without ultrasonic table.