- Unambiguous stereochemical assignment of cyclo(Phe-pro), cyclo(leu-pro), and cyclo(val-pro) by electronic circular dichroic spectroscopy
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2,5-diketopiperazines (DKPs) are cyclic dipeptides ubiquitously found in nature. In particular, cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro) are frequently detected in many microbial cultures. Each of these DKPs has four possible stereoisomers due to the presence of two chirality centers. However, absolute configurations of natural DKPs are often ambiguous due to the lack of a simple, sensitive, and reproducible method for stereochemical assignment. This is an important problem because stereochemistry is a key determinant of biological activity. Here, we report a synthetic DKP library containing all stereoisomers of cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro). The library was subjected to spectroscopic characterization using mass spectrometry, NMR, and electronic circular dichroism (ECD). It turned out that ECD can clearly differentiate DKP stereoisomers. Thus, our ECD dataset can serve as a reference for unambiguous stereochemical assignment of cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro) samples from natural sources. The DKP library was also subjected to a biological screening using assays for E. coli growth and biofilm formation, which revealed distinct biological effects of cyclo(D-Phe-L-Pro).
- Dewan, Faizunnahar,Domzalski, Alison,Kawamura, Akira,Margent, Liliana,Pilarsetty, Naga Vara Kishore,Vigo, Valeria,Xu, Yujia
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- Molecular capture and conformational change of diketopiperazines containing proline residues by epigallocatechin-3-O-gallate in water
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The addition of an aqueous solution of diketopiperazine cyclo(Pro-Xxx) (Xxx: amino acid residue) to an aqueous solution of (?)-epigallocatechin-3-O-gallate (EGCg) led to precipitation of the complex of EGCg and cyclo(Pro-Xxx). The molecular capture abilities of cyclo(Pro-Xxx) using EGCg were evaluated by the ratio of the amount of cyclo(Pro-Xxx) included in the precipitates of the complex with EGCg to that of the total cyclo(Pro-Xxx) used. Stronger hydrophobicity of the side chain of the amino acid residue of cyclo(Pro-Xxx) led to a higher molecular capture ability. Furthermore, the molecular capture ability decreased when the side chain of the amino acid residue had a hydrophilic hydroxyl group. When diketopiperazine cyclo(Pro-Xxx), excluding cyclo(D-Pro-L-Ala), was taken into the hydrophobic space formed by the three aromatic A, B, and B′ rings of EGCg, and formed a complex, their conformation was maintained in the hydrophobic space. Based on nuclear Overhauser effect (NOE) measurement, the 3-position methyl group of cyclo(D-Pro-L-Ala) in D2O was axial, whereas that of cyclo(L-Pro-L-Ala) was equatorial. When cyclo(D-Pro-L-Ala) was taken into the hydrophobic space of EGCg and formed a 2:2 complex, its 3-position methyl group changed from the axial position to the equatorial position due to steric hindrance by EGCg.
- Ishizu, Takashi,Tokunaga, Miku,Fukuda, Moeka,Matsumoto, Mana,Goromaru, Takeshi,Takemoto, Soushi
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p. 585 - 589
(2021/06/06)
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- AGRICULTURAL CHEMICAL CONTAINING 2,5-DIKETOPIPERAZINE DERIVATIVE AS ACTIVE INGREDIENT
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Disclosed herein is an agricultural agent containing a 2,5-diketopiperazine derivative capable of controlling plant diseases and promoting plant growth or an agriculturally acceptable salt thereof as an active ingredient.
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Paragraph 0033
(2013/06/05)
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- A new benzotriazole-mediated stereoflexible gateway to hetero-2,5- diketopiperazines
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Open chain Cbz-L-aa1-L-Pro-Bt (Bt=benzotriazole) sequences were converted into either the corresponding trans- or cis-fused 2,5- diketopiperazines (DKPs) depending on the reaction conditions. Thermodynamic tandem cyclization/epimerization afforded selectively the corresponding trans-DKPs (69-75%). Complementarily, tandem deprotection/cyclization led to the cis-DKPs (65-72%). A representative set of proline-containing cis- and trans-DKPs has been prepared. A mechanistic investigation, based on chiral HPLC, kinetics, and computational studies enabled a rationalization of the results. Stereoflexible route to DKPs: A convenient, versatile, and flexible benzotriazole-mediated methodology for the synthesis of proline-containing hetero-2,5-diketopiperazines (DKPs) is reported. Depending on the reaction conditions, either cis- or trans-configured DKPs were obtained starting from the same inexpensive l,l-dipeptidoyl benzotriazole key intermediate (see scheme). Kinetics, chiral HPLC, and computational studies forged a background for mechanistic rationalization. Copyright
- Monbaliu, Jean-Christophe M.,Hansen, Finn K.,Beagle, Lucas K.,Panzner, Matthew J.,Steel, Peter J.,Todadze, Ekaterina,Stevens, Christian V.,Katritzky, Alan R.
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p. 2632 - 2638
(2012/04/17)
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- Model studies of competing hydrolysis and epimerization of some tetrapeptides of interest in amino acid racemization studies in geochronology
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The processes of epimerization of individual peptide units in proteins and the concurrent cleavage of peptide bonds are modelled by heating some tetrapeptide and tetrapeptide derivatives to 148.5 deg C in pH 6.8 phosphate buffer.An excess of D-proline was observed during the heating of L-propyl-L-leucylglycylglycine.The D/L ratio of proline attains a maximum value of 2.1 after 90 minutes.The excess D-proline is attributed to the formation of a 2.3:1 mixture of diketopiperazines cyclo-(D-propyl-L-leucyl) and cyclo-(L-prolyl-L-leucyl).These two species account for most of the leucine and proline in the final mixture after the tetrapeptide is no longer detectable.Only small amounts of prolylleucine can be detcected after 50 hours.It is suggested that the above tetrapeptide undergoes internal aminolysis.Leucine in the tetrapeptide glycyl-L-leucylglycylglycine racemizes three times faster than in L-propyl-L-leucylglycylglycine.This demonstrates that an amino acid residue in a peptide chain does have an effect upon the rate of epimerization of a neighbouring peptide residue.A discussion of the geochemical implications of the results is included.
- Moir, Michael E.,Crawford, Robert J.
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p. 2903 - 2913
(2007/10/02)
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