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40 results on '"Nishiyama, Yoshitake"'

2. Anticancer Approach Inspired by the Hepatotoxic Mechanism of Pyrrolizidine Alkaloids with Glycosylated Artificial Metalloenzymes

Author

Kurimoto, Michitaka, Chang, Tsung‐che, Nishiyama, Yoshitake, Suzuki, Takehiro, Dohmae, Naoshi, Tanaka, Katsunori, Yokoshima, Satoshi, Kurimoto, Michitaka, Chang, Tsung‐che, Nishiyama, Yoshitake, Suzuki, Takehiro, Dohmae, Naoshi, Tanaka, Katsunori, and Yokoshima, Satoshi

Abstract

Metabolic oxidation of pyrrolizidine alkaloids (PAs) from herbal and dietary supplements by cytochrome P450 produces dehydro-PAs (DHPs), which leads to toxicities. A highly reactive cation species generated from the active pyrrole ring of DHPs readily reacts with various cellular components, causing hepatotoxicity and cytotoxicity. Inspired by PA-induced hepatic damage, we developed a therapeutic approach based on a cyclization precursor that can be transformed into a synthetic DHP under physiological conditions through gold-catalyzed 5-endo-dig cyclization using a gold-based artificial metalloenzyme (ArM) instead of through metabolic oxidation by cytochrome P450. In cell-based assays, the synthesis of the DHP by a cancer-targeting glycosylated gold-based ArM substantially suppressed cell growth of the targeted cancer cells without causing cytotoxicity to untargeted cells, highlighting the potential of the strategy to be used therapeutically in vivo.

Published
2023

15. Total Synthesis of (−)-Cardiopetaline

Author

Nishiyama, Yoshitake, Satoshi Yokoshima, and Fukuyama, Tohru

Abstract

The total synthesis of (−)-cardiopetaline, an aconitine-type natural product, has been accomplished. Our synthesis involved a Wagner–Meerwein rearrangement of a sulfonyloxirane that enabled, in a single step, the construction of the bicyclo[3.2.1] system in the aconitine skeleton and effective introduction of oxygen functional groups at the appropriate positions.

Published
2016

20. Synthesis of benzyl sulfides via substitution reaction at the sulfur of phosphinic acid thioesters.

Author

Nishiyama, Yoshitake, Hosoya, Takamitsu, and Yoshida, Suguru

Subjects
*PHOSPHINIC acid, *SULFUR acids, *THIOESTERS, *METAL sulfides, *GRIGNARD reagents, *DRUG synthesis, *SUBSTITUTION reactions
Abstract

An ambident electrophilicity of phosphinic acid thioesters is disclosed. Unexpected carbon–sulfur bond formation took place in the reaction between phosphinic acid thioesters and benzyl Grignard reagents. The developed method for benzyl sulfides has a wide substrate scope and was applicable for the synthesis of a drug analog. [ABSTRACT FROM AUTHOR]

Published
2020
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27. Synthesis of Cardiopetaline via a Wagner–Meerwein Rearrangement without Preactivation of the Pivotal Hydroxy Group

Author

Nishiyama, Yoshitake, Yokoshima, Satoshi, and Fukuyama, Tohru

Abstract

A synthesis of cardiopetaline has been accomplished via a Wagner–Meerwein rearrangement of a diol having the denudatine skeleton. The Wagner–Meerwein rearrangement could be facilitated simply by heating the diol with p-toluenesulfonic acid in pivalic acid, without preactivating the pivotal hydroxy group. This strategy does not require differentiation of several hydroxy groups in the substrate for the Wagner–Meerwein rearrangement and could be applied to the synthesis of more highly oxygenated aconitine-type diterpenoid alkaloids.

Published
2024
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33. Activity-Dependent Proteolytic Cleavage of Neuroligin-1

Author

Suzuki, Kunimichi, primary, Hayashi, Yukari, additional, Nakahara, Soichiro, additional, Kumazaki, Hiroshi, additional, Prox, Johannes, additional, Horiuchi, Keisuke, additional, Zeng, Mingshuo, additional, Tanimura, Shun, additional, Nishiyama, Yoshitake, additional, Osawa, Satoko, additional, Sehara-Fujisawa, Atsuko, additional, Saftig, Paul, additional, Yokoshima, Satoshi, additional, Fukuyama, Tohru, additional, Matsuki, Norio, additional, Koyama, Ryuta, additional, Tomita, Taisuke, additional, and Iwatsubo, Takeshi, additional

Published
2012
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36. Total Synthesis of (–)-Lepenine.

Author

Nishiyama, Yoshitake, Han-ya, Yuki, Yokoshima, Satoshi, and Fukuyama, Tohru

Subjects
*CHEMICAL reactions, *ETHYLENE, *ALKENES, *MANNICH reaction, *DIELS-Alder reaction, *STEREOCHEMISTRY
Abstract

The first asymmetric total synthesis of lepenine has been accomplished. The synthesis features a tethered intramolecular Diels–Alder reaction, an intramolecular Mannich reaction, and a Diels–Alder reaction between an ortho-quinone monoketal and ethylene, resulting in stereoselective construction of the unique hexacyclic system. [ABSTRACT FROM AUTHOR]

Published
2014
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37. Membrane dynamics as seen by Fourier transform infrared spectroscopy in a cyanobacterium, SynechocystisPCC 6803

Author

Szalontai, Balázs, Nishiyama, Yoshitake, Gombos, Zoltán, and Murata, Norio

Abstract

The roles of lipid unsaturation and lipid-protein interactions in maintaining the physiologically required membrane dynamics were investigated in a cyanobacterium strain, SynechocystisPCC 6803. The specific effects of lipid unsaturation on the membrane structure were addressed by the use of desaturase-deficient (desA−/desD−) mutant cells (which contain only oleic acid as unsaturated fatty acid species) of SynechocystisPCC 6803. The dynamic properties of the membranes were determined from the temperature dependence of the symmetric CH2stretching vibration frequency, which is indicative of the lipid fatty acyl chain disorder. It was found that a similar membrane dynamics is maintained at any growth temperature, in both the wild-type and the mutant cell membranes, with the exception of mutant cells grown at the lower physiological temperature limit. It seems that in the physiological temperature range the desaturase system of the cells can modulate the level of lipid desaturation sufficiently to maintain similar membrane dynamics. Below the range of normal growth temperatures, however, the extent of lipid disorder was always higher in the thylakoid than in the cytoplasmic membranes prepared from the same cells. This difference was attributed to the considerable difference in protein-to-lipid ratio in the two kinds of membranes, as determined from the ratio of the intensities of the protein amide I band and the lipid ester C=O vibration. The contributions to the membrane dynamics of an ab ovo present ‘structural’ lipid disorder due to the protein–lipid interactions and of a thermally induced ‘dynamic’ lipid disorder could be distinguished.

Published
2000
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38. Membrane dynamics as seen by Fourier transform infrared spectroscopy in a cyanobacterium, Synechocystis PCC 6803 The effects of lipid unsaturation and the protein-to-lipid ratio

Author

Szalontai, Balázs, Nishiyama, Yoshitake, Gombos, Zoltán, and Murata, Norio

Subjects
(Synechocystis PCC 6803), Fourier transform infrared spectroscopy, lipids (amino acids, peptides, and proteins), Membrane dynamics, Desaturase deficient mutant, Lipid, Protein-to-lipid ratio
Abstract

The roles of lipid unsaturation and lipid-protein interactions in maintaining the physiologically required membrane dynamics were investigated in a cyanobacterium strain, Synechocystis PCC 6803. The specific effects of lipid unsaturation on the membrane structure were addressed by the use of desaturase-deficient (desA−/desD−) mutant cells (which contain only oleic acid as unsaturated fatty acid species) of Synechocystis PCC 6803. The dynamic properties of the membranes were determined from the temperature dependence of the symmetric CH2 stretching vibration frequency, which is indicative of the lipid fatty acyl chain disorder. It was found that a similar membrane dynamics is maintained at any growth temperature, in both the wild-type and the mutant cell membranes, with the exception of mutant cells grown at the lower physiological temperature limit. It seems that in the physiological temperature range the desaturase system of the cells can modulate the level of lipid desaturation sufficiently to maintain similar membrane dynamics. Below the range of normal growth temperatures, however, the extent of lipid disorder was always higher in the thylakoid than in the cytoplasmic membranes prepared from the same cells. This difference was attributed to the considerable difference in protein-to-lipid ratio in the two kinds of membranes, as determined from the ratio of the intensities of the protein amide I band and the lipid ester CO vibration. The contributions to the membrane dynamics of an ab ovo present ‘structural’ lipid disorder due to the protein–lipid interactions and of a thermally induced ‘dynamic’ lipid disorder could be distinguished.

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39. Anticancer Approach Inspired by the Hepatotoxic Mechanism of Pyrrolizidine Alkaloids with Glycosylated Artificial Metalloenzymes.

Author

Kurimoto M, Chang TC, Nishiyama Y, Suzuki T, Dohmae N, Tanaka K, and Yokoshima S

Subjects
Cytochrome P-450 Enzyme System, Pyrroles metabolism, Gold, Pyrrolizidine Alkaloids toxicity, Metalloproteins
Abstract

Metabolic oxidation of pyrrolizidine alkaloids (PAs) from herbal and dietary supplements by cytochrome P450 produces dehydro-PAs (DHPs), which leads to toxicities. A highly reactive cation species generated from the active pyrrole ring of DHPs readily reacts with various cellular components, causing hepatotoxicity and cytotoxicity. Inspired by PA-induced hepatic damage, we developed a therapeutic approach based on a cyclization precursor that can be transformed into a synthetic DHP under physiological conditions through gold-catalyzed 5-endo-dig cyclization using a gold-based artificial metalloenzyme (ArM) instead of through metabolic oxidation by cytochrome P450. In cell-based assays, the synthesis of the DHP by a cancer-targeting glycosylated gold-based ArM substantially suppressed cell growth of the targeted cancer cells without causing cytotoxicity to untargeted cells, highlighting the potential of the strategy to be used therapeutically in vivo., (© 2022 Wiley-VCH GmbH.)

Published
2022
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40. Total Synthesis of (-)-Cardiopetaline.

Author

Nishiyama Y, Yokoshima S, and Fukuyama T

Abstract

The total synthesis of (-)-cardiopetaline, an aconitine-type natural product, has been accomplished. Our synthesis involved a Wagner-Meerwein rearrangement of a sulfonyloxirane that enabled, in a single step, the construction of the bicyclo[3.2.1] system in the aconitine skeleton and effective introduction of oxygen functional groups at the appropriate positions.

Published
2016
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