Yoko Ikeda

Bio: Yoko Ikeda is an academic researcher from Keio University. The author has contributed to research in topics: Arbekacin & Aminoglycoside. The author has an hindex of 20, co-authored 83 publications receiving 1258 citations.

Chloptosin, an apoptosis-inducing dimeric cyclohexapeptide produced by Streptomyces.

Abstract: In the course of screening for apoptosis-inducing agents, chloptosin (1) was isolated from the culture broth of Streptomyces. The dumbbell-type structure of the dimeric cyclohexapeptide consisting of d-valine, (3S)- and (3R)-piperazic acids, O-methyl-l-serine, d-threonine, and (2S,3aR,8aR)-6-chloro-3a-hydroxy-2,3,3a,8a-hexahydropyrrolo[2,3-b]indole-2-carboxylic acid was elucidated by spectroscopic and chemical degradation studies. The amino acid components in each cyclohexapeptide domain were presented in alternating R and S configurations. Chloptosin (1) was found to induce apoptotic activity in apoptosis-resistant human pancreatic adenocarcinoma cell line AsPC-1 and showed a strong antimicrobial activity against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus.

Polyoxypeptins A and B Produced by Streptomyces: Apoptosis-Inducing Cyclic Depsipeptides Containing the Novel Amino Acid (2S,3R)-3-Hydroxy-3-methylproline.

Abstract: Potent apoptosis-inducing peptides, polyoxypeptins A (1) and B (2) were isolated from the culture broth of Streptomyces sp. by solvent extraction and column chromatography. Structural elucidation of 1 by MS and NMR analyses revealed that it is a cyclic hexadepsipeptide having a novel amino acid and a previously unrecognized N-acyl side chain. The depsipeptide consisted of 3-hydroxyleucine, N-hydroxyvaline, N-hydroxyalanine, piperazic acid, 5-hydroxyhexahydropiperazine-3-carboxylic acid, and an unusual and hitherto unreported amino acid, 3-hydroxy-3-methylproline. Alanine and valine obtained from the hydrolyzate of 1 were both in the L-configuration as concluded from chiral TLC analysis. Then, the absolute structure of 1 was determined with the relative structure obtained from X-ray crystallographic analysis, and the new amino acid was isolated and confirmed to be (2S,3R)-3-hydroxy-3-methylproline (3). MS and NMR of 2 exhibited that it is a monodeoxy compound of 1. Stereochemistry of 2 was determined by degradation studies. Both 1 and 2 at a concentration of about 0.1 mg/mL induced early cell death, nuclear fragmentation, and internucleosomal DNA scission, all of which are characteristic of apoptosis, in human pancreatic carcinoma AsPC-1 cells.

Palladium-catalyzed cross-coupling reactions in total synthesis.

Abstract: In studying the evolution of organic chemistry and grasping its essence, one comes quickly to the conclusion that no other type of reaction plays as large a role in shaping this domain of science than carbon-carbon bond-forming reactions. The Grignard, Diels-Alder, and Wittig reactions are but three prominent examples of such processes, and are among those which have undeniably exercised decisive roles in the last century in the emergence of chemical synthesis as we know it today. In the last quarter of the 20th century, a new family of carbon-carbon bond-forming reactions based on transition-metal catalysts evolved as powerful tools in synthesis. Among them, the palladium-catalyzed cross-coupling reactions are the most prominent. In this Review, highlights of a number of selected syntheses are discussed. The examples chosen demonstrate the enormous power of these processes in the art of total synthesis and underscore their future potential in chemical synthesis.

Aminoglycosides: Activity and Resistance

Abstract: Aminoglycosides are highly potent, broad-spectrum antibiotics with many desirable properties for the treatment of life-threatening infections ([28][1]). Their history begins in 1944 with streptomycin and was thereafter marked by the successive introduction of a series of milestone compounds (