Jaehoon Sim

Asymmetric syntheses of 1-deoxy-6,8a-di-epi-castanospermine and 1-deoxy-6-epi-castanospermine.

Asymmetric syntheses of both 1-deoxy-6,8a-di-epi-castanospermine and 1-deoxy-6-epi-castanospermine, polyhydroxylated indolizidine alkaloids that act as selective glycosidase inhibitors, have been accomplished in seven steps. The key feature of our unique syntheses includes the stereoselective introduction of the C-3 and C-4 hydroxyl groups utilizing the aza-Claisen rearrangement-induced ring expansion of 1-acyl-2-alkoxyvinyl pyrrolidine and a substrate-controlled stereoselective transannulation of the resulting azoninone intermediate.

Approach of Team SNU to the DARPA Robotics Challenge finals

This paper presents the technical approaches including the system architecture and the controllers that have been used by Team SNU at the DARPA Robotics Challenge (DRC) Finals 2015. The platform THORMANG we used is a modular humanoid robot developed by ROBOTIS. On top of this platform, Team SNU developed the iris camera module and the end effector with passive palm in order to increase success rate of the tasks at the DRC Finals. Also, we developed the software architecture to operate the robot intuitively, in spite of degraded communication. The interface enables operator to select sensor data to be communicated during each task. These efforts on the hardware and the software reduce operation time of the tasks, and increase reliability of the robot. Finally, the controllers for THORMANG were developed to consider stability as the first priority, because the humanoid robot for rescue should perform complex tasks in unexpected environments. The proposed approaches were verified at the DRC Finals 2015, where Team SNU ranked 12th place out of 23 teams.

Nicrophorusamides A and B, Antibacterial Chlorinated Cyclic Peptides from a Gut Bacterium of the Carrion Beetle Nicrophorus concolor

Nicrophorusamides A and B (1 and 2) were discovered from a rare actinomycete, Microbacterium sp., which was isolated from the gut of the carrion beetle Nicrophorus concolor. The structures of the nicrophorusamides were established as new chlorinated cyclic hexapeptides bearing uncommon amino acid units mainly based on 1D and 2D NMR spectroscopic analysis. The absolute configurations of the amino acid residues 5-chloro-l-tryptophan, d-threo-β-hydroxyasparagine/d-asparagine, l-ornithine, l-allo-isoleucine, d-leucine, and d-valine were determined using Marfeys method and chemical derivatization with 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl isothiocyanate followed by LC/MS analysis. Nicrophorusamide A (1) showed antibacterial activity against several Gram-positive bacteria.

Team SNU's Control Strategies for Enhancing a Robot's Capability: Lessons from the 2015 DARPA Robotics Challenge Finals

This paper presents the technical approaches used and experimental results obtained by Team SNU Seoul National University at the 2015 DARPA Robotics Challenge DRC Finals. Team SNU is one of the newly qualified teams, unlike 12 teams who previously participated in the December 2013 DRC Trials. The hardware platform THORMANG, which we used, has been developed by ROBOTIS. THORMANG is one of the smallest robots at the DRC Finals. Based on this platform, we focused on developing software architecture and controllers in order to perform complex tasks in disaster response situations and modifying hardware modules to maximize manipulability. Ensuring stability and modularization are two main keywords in the technical approaches of the architecture. We designed our interface and controllers to achieve a higher robustness level against disaster situations. Moreover, we concentrated on developing our software architecture by integrating a number of modules to eliminate software system complexity and programming errors. With these efforts on the hardware and software, we successfully finished the competition without falling, and we ranked 12th out of 23 teams. This paper is concluded with a number of lessons learned by analyzing the 2015 DRC Finals.

Practical and efficient synthesis of gefitinib through selective O-alkylation: A novel concept for a transient protection group

ABSTRACT A practical process that includes a simple four-step procedure for the preparation of gefitinib (1), a tyrosine kinase inhibitor that targets the epidermal growth factor receptor, is described. Dramatic improvements over previously reported conventional synthetic procedures were achieved. We found effective coupling conditions to minimize the inevitable production of an N-alkylated side product, N-(3-chloro-4-fluorophenyl)-7-methoxy-6-(3-morpholinopropoxy)-N-(3-morpholinopropyl)-quinazoline-4-amine (3) using a transient trimethylsilyl protecting group. We synthesized gefitinib in an 81.1% overall yield from a commercially available starting material on a multigram scale using a route that did not require work-up of any of the reaction steps. GRAPHICAL ABSTRACT

SYNTHESIS AND SYNTHESIS-BASED STRUCTURAL ELUCIDATION OF (-)-MACROSPHELIDES J AND K

Hongchan An, Seung-Hee Kim, Heegyu Kim, Kyeojin Kim, Jaehoon Sim, Jaebong Jang, Seung-Mann Paek, Young-Ger Suh, and Hwayoung Yun* a College of Pharmacy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151742, Korea b College of Pharmacy, Pusan National University, Geumjeong-gu, Busan 609-735, Korea c College of Pharmacy, Research Institute of Pharmaceutical Sciences, Gyeongsang National University, Jinju daero, Jinju, Gyeongnam 660-751, Korea

Stereoselective Synthesis of 1,4,5-Tri-cis-guaiane Sesquiterpene: First Total Synthesis of (−)-Dendroside C Aglycon

The first total synthesis of (-)-dendroside C aglycon, consisting of a 1,4,5-tri-cis-guaiane skeleton, from a versatile hydroazulene intermediate has been accomplished. The key features of the syntheses include the stereoselective preparation of the unusual cis-hydroazulene core via a sequence of a unique Dieckmann condensation of the bicyclic lactone system, which was concisely prepared by the tandem conjugate addition and intramolecular allylic alkylation of a butenolide precursor, and construction of the characteristic tricyclic skeleton by a carbene-mediated cyclopropanation.

Team SNU’s Control Strategies to Enhancing Robot’s Capability: Lessons from the DARPA Robotics Challenge Finals 2015

This paper presents the technical approaches used and experimental results obtained by Team SNU at the DARPA Robotics Challenge (DRC) Finals 2015. Team SNU is one of the newly qualified teams, unlike the 12 teams who previously participated in the December 2013 DRC Trials. The hardware platform THORMANG, which we used, has been developed by ROBOTIS. THORMANG is one of the smallest robots at the DRC Finals. Based on this platform, we focused on developing software architecture and controllers in order to perform complex tasks in disaster response situations and modifying hardware modules to maximize manipulability. Ensuring stability and modularization are two main keywords in the technical approaches of the architecture. We designed our interface and controllers to achieve a higher robustness level against disaster situations. Moreover, we concentrated on developing our software architecture by integrating a number of modules to eliminate software system complexity and programming errors. With these efforts on the hardware and software, we have successfully finished the competition without falling and ranked 12th out of 23 teams. This paper is concluded with a number of lessons learned by analyzing the DRC Finals 2015.

Asymmetric Total Synthesis of (+)-(3E)-Pinnatifidenyne via Abnormally Regioselective Pd(0)-Catalyzed Endocyclization

The asymmetric total synthesis of the marine natural product (+)-(3E)-pinnatifidenyne was accomplished. The key features of the synthesis involve the construction of an eight-membered cyclic ether by the abnormally regioselective Pd(0)-catalyzed cyclization, the installation of a double bond in the oxocene skeleton by sequential in situ deconjugative isomerization, and the efficient introduction of the crucial chloride mediated by the substrate-controlled diastereoselective reduction.

Novel Hypoxia-Inducible Factor 1α (HIF-1α) Inhibitors for Angiogenesis-Related Ocular Diseases: Discovery of a Novel Scaffold via Ring-Truncation Strategy

Ocular diseases featuring pathologic neovascularization are the leading cause of blindness, and anti-VEGF agents have been conventionally used to treat these diseases. Recently, regulating factors upstream of VEGF, such as HIF-1α, have emerged as a desirable therapeutic approach because the use of anti-VEGF agents is currently being reconsidered due to the VEGF action as a trophic factor. Here, we report a novel scaffold discovered through the complete structure-activity relationship of ring-truncated deguelin analogs in HIF-1α inhibition. Interestingly, analog 6i possessing a 2-fluorobenzene moiety instead of a dimethoxybenzene moiety exhibited excellent HIF-1α inhibitory activity, with an IC50 value of 100 nM. In particular, the further ring-truncated analog 34f, which showed enhanced HIF-1α inhibitory activity compared to analog 2 previously reported by us, inhibited in vitro angiogenesis and effectively suppressed hypoxia-mediated retinal neovascularization. Importantly, the heteroatom-substituted benzene ring as a key structural feature of analog 34f was identified as a novel scaffold for HIF-1α inhibitors that can be used in lieu of a chromene ring.