Browsing by Author "Chang, Chieh-Yu"

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An efficient synthesis of the C27-C45 fragment of lagunamide A, a cyclodepsipeptide with potent cytotoxic and antimalarial properties
(2014-01-31)
Liu, Hui-Ming
;
Chang, Chieh-Yu
;
Lai, Ya-Chi
;
Yang, Mei-Due
;
Chang, Ching-Yao
An efficient and stereoselective synthesis of the entire C27-C45 moiety of lagunamide A has been achieved from 1-[(4S)-4-benzyl-2-thioxothiazolidin-3-yl]propan-1-one in six steps with 22% overall yield. The key step in the synthesis is an asymmetric acetal aldol reaction featuring the enantioselective addition of a chiral thiazolidinethione-derived titanium enolate to an acetal to establish the stereochemistry at C39. (C) 2013 Elsevier Ltd. All rights reserved.
Formal synthesis of schulzeines B and C: A new route to Gurjar's lactams
(1970-01-01)
Chou, Chu-En
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Chen, Yi-An
;
Lin, Yi-Ching
;
Kao, Shih-Chieh
;
Chang, Chieh-Yu
Described is a formal synthesis of racemic schulzeines B and C that intercepts intermediates developed by Gurjar and co-workers. The synthetic sequence features an annulative coupling of a ketimine and acrylic acid enabling the construction of the benzoquinolizidine nucleus in a highly convergent manner. We also examined a continuous-flow version of the thermal aza-annulation, which proved less practical as compared to the batch processes.
Optical properties of plasma-enhanced chemical vapor deposited SiCxNy films by using silazane precursors
(2017-08-31)
Chang, Wei-Yuan
;
Chang, Chieh-Yu
;
Leu, Jihperng
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材料科學與工程學系
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Department of Materials Science and Engineering
In this study, amorphous silicon carbonitride (SiCxNy) films were fabricated by radio frequency (RF) chemical vapor deposition (PECVD) using a single silazane precursor and a low power density (0.15W/cm(3)) for better compositional control. The effects of the precursor chemical structure (C/Si ratio, C-Si-N structure, and vinyl groups) and deposition temperature (T-s) on the chemical structure and optical properties of SiCxNy films were examined using Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Specifically, two new single precursors; namely, n-methyl-aza-2,2,4-trimethylsilacyclopentane (MTSCP) and 1,3-divinyl-1,1,3,3-tetramethyl-disilazane (DVTMDS) were studied and compared. SiCxNy films deposited using MTSCP involving Si-C-3-N rings formed Si-N and Si-(CH2)(3)-crosslinked structures at T-s <= 100 degrees C, and were then changed to predominantly Si-CH2-N-Si crosslinked structures at Ts > 300 degrees C, leading to a wide range of optical band gap from 5.2 to 3.7 eV. Compared to DVTMDS-deposited SiCxNy films, their relatively higher percentage of Si-C-N structure accounted for the lower optical band gap and reduced transmission. DVTMDS with di-vinyl groups readily formed a Si-(CH2)(2)-bridge in SiCxNy films Ts <= 200 degrees C, resulting in excellent optical transmittance. The transmittance in the visible wavelengths of 400 degrees C-deposited SiCxNy film using DVTMDS still showed 85%. Also, tunable refractive index between 1.44 and 2.10 were obtained for SiCxNy films deposited at T-s <= 400 degrees C. (c) 2017 Elsevier B.V. All rights reserved.
Palladium-Catalyzed alpha-Allylation of Secondary Nitroalkanes with Allylic Alcohols and Strategic Exploitation of Seebach's Reagent for the Total Synthesis of (+/-)-Adalinine
(2018-06-01)
Chang, Chieh-Yu
;
Wu, Yen-Ku
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應用化學系
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Department of Applied Chemistry
A method is reported for the catalytic direct coupling of allylic alcohols and nitroalkanes. the allylation process, the synergistic action of palladium complexes and titanium(IV) alkoxide facilitates the formation of nitronate and pi-allylpalladium intermediate. In the cases of reluctant allylations, typically with sterically demanding nitroalkanes, we found the addition of substoichiometric amount of DBU greatly facilitates the desired transformation. We also accomplished a total synthesis of (+/-)-adalinine through a homoallyl nitroalkane derived from Seebach's reagent.
Palladium-catalyzed N1-selective allylation of indoles with allylic alcohols promoted by titanium tetraisopropoxide
(2019-01-25)
Chang, Chieh-Yu
;
Lin, Yu-Huan
;
Wu, Yen-Ku
;
應用化學系
;
Department of Applied Chemistry
The direct N1-selective allylation of indoles with allylic alcohols has been accomplished by synergistic functions of palladium catalysts and titanium tetraisopropoxide. The site selectivity is notably different from that observed in other related transition metal-catalyzed approaches. This chemistry provides a facile route to a variety of allylated indoles in synthetically useful yields. The utility of this simple allylation reaction was demonstrated with the first total synthesis of (+)-N-(4-hydroxyprenyl)-cyclo(alanyltryptophyl), which was completed in five steps, starting from l-tryptophan methyl ester hydrochloride.
PSPC1 mediates TGF-beta 1 autocrine signalling and Smad2/3 target switching to promote EMT, stemness and metastasis
(2018-04-01)
Yeh, Hsi-Wen
;
Hsu, En-Chi
;
Lee, Szu-Shuo
;
Lang, Yaw-Dong
;
Lin, Yuh-Charn
Activation of metastatic reprogramming is critical for tumour metastasis. However, more detailed knowledge of the underlying mechanism is needed to enable targeted intervention. Here, we show that paraspeckle component 1 (PSPC1), identified in an aberrant 13q12.11 locus, is upregulated and associated with poor survival in patients with cancer. PSPC1 promotes tumorigenesis, epithelial-to-mesenchymal transition (EMT), stemness and metastasis in multiple cell types and in spontaneous mouse cancer models. PSPC1 is the master activator for transcription factors of EMT and stemness and accompanies c-Myc activation to facilitate tumour growth. PSPC1 increases transforming growth factor-ss 1 (TGF-ss 1) secretion through an interaction with phosphorylated and nuclear Smad2/3 to potentiate TGF-ss 1 autocrine signalling. Moreover, PSPC1 acts as a contextual determinant of the TGF-ss 1 pro-metastatic switch to alter Smad2/3 binding preference from tumour-suppressor to pro-metastatic genes. Having validated the PSPC1-Smads-TGF-ss 1 axis in various cancers, we conclude that PSPC1 is a master activator of prometastatic switches and a potential target for anti-metastasis drugs.