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Asymmetric Synthesis of Biaryl Diols via Dynamic Kinetic Resolution
Cho Jeonghun,Kim Kyungwoo,Park Jaiwook,Kim Mahn‐Joo 대한화학회 2021 Bulletin of the Korean Chemical Society Vol.42 No.7
We have developed a protocol incuding dynamic kinetic resolution as the key step for the asymmetric synthesis of biaryl diol stereoisomers. The two aryl alkanols as the starting materials were cross-coupled by palladium catalysis to give dl- and meso-diol, which were then subject to chemoenzymatic dynamic kinetic resolution (DKR) for the transformation into single stereoisomeric diol diester. Diol diester was finally deacylated to give the corresponding biaryl diol stereoisomer. The chemoenzymatic DKR was performed with a ruthenium-based racemization catalyst and a (R)-selective lipoprotein lipase. Total 17 (R, R)-diols including 7 C2-symmetric diols were synthesized with excellent enantiopurities (>99% ee).
High-Mobility Pyrene-Based Semiconductor for Organic Thin-Film Transistors
Cho, Hyunduck,Lee, Sunyoung,Cho, Nam Sung,Jabbour, Ghassan E.,Kwak, Jeonghun,Hwang, Do-Hoon,Lee, Changhee American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.9
<P>Numerous conjugated oligoacenes and polythiophenes are being heavily studied in the search for high-mobility organic semiconductors. Although many researchers have designed fused aromatic compounds as organic semiconductors for organic thin-film transistors (OTFTs), pyrene-based organic semiconductors with high mobilities and on–off current ratios have not yet been reported. Here, we introduce a new pyrene-based p-type organic semiconductor showing liquid crystal behavior. The thin film characteristics of this material are investigated by varying the substrate temperature during the deposition and the gate dielectric condition using the surface modification with a self-assembled monolayer, and systematically studied in correlation with the performances of transistor devices with this compound. OTFT fabricated under the optimum deposition conditions of this compound, namely, 1,6-bis(5′-octyl-2,2′-bithiophen-5-yl)pyrene (BOBTP) shows a high-performance transistor behavior with a field-effect mobility of 2.1 cm<SUP>2</SUP> V<SUP>–1</SUP> s<SUP>–1</SUP> and an on–off current ratio of 7.6 × 10<SUP>6</SUP> and enhanced long-term stability compared to the pentacene thin-film transistor.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-9/am4005368/production/images/medium/am-2013-005368_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am4005368'>ACS Electronic Supporting Info</A></P>
조정훈(JEONGHUN CHO),백윤흥(YUNHEUNG PAEK),최준식(JUNSIK CHOI) 한국정보과학회 2003 한국정보과학회 학술발표논문집 Vol.30 No.2Ⅰ
Virtually every digital signal processors(DSPs) support on-chip multi- memory banks that allow the processor to access multiple words of data from memory in a single instruction cycle. Also, all existing fixed-point DSPs have irregular architecture of heterogeneous register which contains multiple register files that arc distributed and dedicated to different sets of instructions. Although there have been several studies conducted to efficiently assign data to multi-memory banks, most of them assumed processors with relatively simple, homogeneous general-purpose registers. Therefore, several vendor-provided compilers for DSPs were unable to efficiently assign data to multiple data memory banks, thereby often failing to generate highly optimized code for their machines. This paper presents an algorithm that helps the compiler to efficiently assign data to multi- memory banks. Our algorithm differs from previous work in that it assigns variables to memory banks in separate, decoupled code generation phases, instead of a single, tightly-coupled phase. The experimental results have revealed that our decoupled algorithm greatly simplifies our code generation process; thus our compiler runs extremely fast, yet generates target code that is comparable in quality to the code generated by a coupled approach.
Noncovalent Interactions of DNA Bases with Naphthalene and Graphene
Cho, Yeonchoo,Min, Seung Kyu,Yun, Jeonghun,Kim, Woo Youn,Tkatchenko, Alexandre,Kim, Kwang S. American Chemical Society 2013 Journal of chemical theory and computation Vol.9 No.4
<P>The complexes of a DNA base bound to graphitic systems are studied. Considering naphthalene as the simplest graphitic system, DNA base–naphthalene complexes are scrutinized at high levels of ab initio theory including coupled cluster theory with singles, doubles, and perturbative triples excitations [CCSD(T)] at the complete basis set (CBS) limit. The stacked configurations are the most stable, where the CCSD(T)/CBS binding energies of guanine, adenine, thymine, and cytosine are 9.31, 8.48, 8.53, 7.30 kcal/mol, respectively. The energy components are investigated using symmetry-adapted perturbation theory based on density functional theory including the dispersion energy. We compared the CCSD(T)/CBS results with several density functional methods applicable to periodic systems. Considering accuracy and availability, the optB86b nonlocal functional and the Tkatchenko–Scheffler functional are used to study the binding energies of nucleobases on graphene. The predicted values are 18–24 kcal/mol, though many-body effects on screening and energy need to be further considered.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jctcce/2013/jctcce.2013.9.issue-4/ct301097u/production/images/medium/ct-2012-01097u_0007.gif'></P>
Cho, Hyunduck,Kwak, Jeonghun,Lim, Jaehoon,Park, Myeongjin,Lee, Donggu,Bae, Wan Ki,Kim, Youn Sang,Char, Kookheon,Lee, Seonghoon,Lee, Changhee American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.20
<P>To realize the full-color displays using colloidal nanocrystal quantum dot (QD)-based light emitting diodes (QLEDs), the emissive QD layer should be patterned to red (R), green (G), and blue (B) subpixels on a micrometer scale by the solution process. Here, we introduced a soft contact QD-transplanting technique onto the vacuum-deposited small molecules without pressure to pattern the QD layer without any damage to the prior organic layers. We examined the patternability of QDs by studying the surface properties of various organic layers systematically. As a result, we found that the vacuum-deposited 4,4′,4″-tri(<I>N</I>-carbazolyl)triphenylamine (TCTA) layer is suitable for QD-transplanting. A uniform and homogeneous QD patterns down to 2 μm could be formed for all the RGB QDs (CdSe/CdS/ZnS, CdSe@ZnS, and Cd<SUB>1–<I>x</I></SUB>Zn<SUB><I>x</I></SUB>S@ZnS, respectively) with this method. Finally, we demonstrated the R, G, and B QLEDs by transplanting each QD onto the soft TCTA layer, exhibiting higher brightness (2497, 14 102, and 265 cd m<SUP>–2</SUP>, respectively) and efficiency (1.83, 8.07, and 0.19 cd A<SUP>–1</SUP>, respectively) than those of the previous QLEDs fabricated by other patterning methods. Because this pressure-free technique is essential for patterning and stacking the QDs onto the soft organic layer, we believe that both fundamental study and the engineering approach presented here are meaningful for the realization of the colloidal QD-based full-color displays and other optoelectronic devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-20/acsami.5b01738/production/images/medium/am-2015-01738a_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b01738'>ACS Electronic Supporting Info</A></P>
Cho, Sangwoo,Ku, Jeonghun,Park, Jinsick,Han, Kiwan,Lee, Hyeongrae,Choi, You Kyong,Jung, Young-Chul,Namkoong, Kee,Kim, Jae-Jin,Kim, In Young,Kim, Sun I.,Shen, Dong Fan Mary Ann Liebert 2008 Cyber Psychology & Behavior Vol.11 No.3
<P>Alcoholism is a disease that affects parts of the brain that control emotion, decisions, and behavior. Therapy for people with alcoholism must address coping skills for facing high-risk situations. Therefore, it is important to develop tools to mimic such conditions. Cue exposure therapy (CET) provides high-risk situations during treatment, which raises the individual's ability to recognize that alcohol craving is being induced. Using CET, it is hard to simulate situations that induce alcohol craving. By contrast, virtual reality (VR) approaches can present realistic situations that cannot be experienced directly in CET. Therefore, we hypothesized that is possible to model social pressure situations using VR. We developed a VR system for inducing alcohol craving under social pressure situations and measured both the induced alcohol craving and head gaze of participants. A 2 x 2 experimental model (alcohol-related locality vs. social pressure) was designed. In situations without an avatar (no social pressure), more alcohol craving was induced if alcohol was present than if it was not. And more alcohol craving was induced in situations with an avatar (social pressure) than in situations without an avatar (no social pressure). The difference of angle between the direction of head gazing and the direction of alcohol or avatar was smaller in situations with an avatar alone (social pressure) than in situations with alcohol alone. In situations with both alcohol and an avatar, the angle between the direction of head gaze and the direction of the avatar was smaller than between the direction of head gaze and the direction of the alcohol. Considering the results, this VR system induces alcohol craving using an avatar that can express various social pressure situations.</P>