25518-39-2Relevant articles and documents
Calyxamides A and B, cytotoxic cyclic peptides from the marine sponge Discodermia calyx
Kimura, Miki,Wakimoto, Toshiyuki,Egami, Yoko,Tan, Karen Co,Ise, Yuji,Abe, Ikuro
experimental part, p. 290 - 294 (2012/05/05)
Cyclic peptides containing 5-hydroxytryptophan and thiazole moieties were isolated from the marine sponge Discodermia calyx collected near Shikine-jima Island, Japan. The structures of calyxamides A (1) and B (2), including the absolute configurations of all amino acids, were elucidated by spectroscopic analyses and degradation experiments. The structures are similar to keramamides F and G, previously isolated from Theonella sp. The analysis of the 16S rDNA sequences obtained from the metagenomic DNA of D. calyx revealed the presence of Candidatus Entotheonella sp., an unculturable δ-proteobacterium inhabiting the Theonella genus and implicated in the biosynthesis of bioactive peptides.
Chiral Discrimination in the Liquid Phase: Excess Volumes of Binary Mixtures of Amino Acid Derivatives
Lepori, Luciano,Koppenhoefer, Beenhard
, p. 6862 - 6864 (2007/10/02)
Volume changes on mixing the enantiomers of N-trifluoroacetylamino acid methyl esters (N-TFA-amino acid-OMe) were determined at 25 deg C by means of a high-precision vibrating-tube densimeter.The excess molar volume (VE) for the racemic mixtures of N-TFA-Ala-OMe 1, N-TFA-Val-OMe 2, and N-TFA-Leu-OMe 3, were found as VE = 0.0098, -0.0458, and 0.035 cm3 mol-1, respectively.For 2 and 3, these volumetric effects of discriminating interactions between enantiomers in the liquid phase are the largest ever observed.
