Structure Of Cyclo Research Articles

Gypsins A−D from Gypsophila arabica

Four new cyclopeptides, named gypsins A-D (1- 4), together with one known oleanane saponin, were isolated from the roots of Gypsophila arabica. The structures of cyclo(-Leu(1)-Pro(2)-Leu(3)-Trp(4)-Pro(5)-Gly(6)-) (1), cyclo(-Leu(1)-Pro(2)-Tyr(3)-Phe(4)-Pro(5)-Gly(6)-) (2), cyclo(-Ala(1)-Pro(2)-Tyr(3)-Leu(4)-Leu(5)-Pro (6)-Pro(7)-Ala(8)-) (3), and cyclo(-Leu(1)-Trp(2)-Pro(3)-Gly(4)-Gly(5)-Ser(6)-Ser(7)-) (4) were elucidated by 1D and 2D NMR spectroscopy including 1D-TOCSY, DQF-COSY, 2D-ROESY, HSQC, and HMBC experiments, as well as ESI tandem mass spectrometric fragmentation analysis and chemical evidence.

Investigation of structures and properties of cyclic peptide nanotubes by experiment and molecular dynamics

In order to investigate the structures and properties of cyclic peptide nanotubes of cyclo[(-D: -Phe-L: -Ala)( n = 3,4,5,6)-], cyclo[(-D: -Phe-L: -Ala)( n = 4)-] was synthesized and self-assembled to nanotubes, and its structure and morphology of the nanotube were characterized by mass spectrometry (MS), fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). On the basis of these experimental results, the structures of cyclo[(-D: -Phe-L: -Ala)( n = 3,4,5,6)-] were characterized by molecular dynamics. In addition, the motion behaviors of H(2)O molecules in nanotubes were investigated by molecular dynamics using a COMPASS force field. Experimental results show that cyclo[(-D: -Phe-L: -Ala)( n = 4)-] peptides self-assemble into nanotube bundles. Molecular modeling results indicate that cyclic peptide nanotubes with n = 3, 4, 5 and 6 are very stable; these nanotubes have internal diameters of 5.9 A, 8.1 A, 10.8 A and 13.1 A and outer diameters of 18.2 A, 21.7 A, 23.4 A and 25.9 A respectively. Modeling results demonstrate that H(2)O molecules move in cooperation in single nanotube and they diffuse in one dimension, but they did not diffuse unilaterally due to the antiparallel ring stacking arrangement.

Electron impact ionization and ion reactions in n-butane

Absolute cross sections for electron impact ionization of n-butane (n-C4H10) as functions of electron energy from 10 to 200 eV have been measured by Fourier transform mass spectrometry. The major ions including the parent ion and eight fragment ions , and are observed, with the total cross section reaching a maximum of 1.18 × 10−15 cm2 at ∼80 eV. Studies of reactions of the major ionization product ions with n-C4H10 have been carried out, showing that , and are unreactive while the remaining ions react readily forming as the common product ion by hydride transfer. The observed reactivities of and combined with the calculated reaction enthalpies for their hydride transfer suggest that these two ions have the structures of cyclo- and cyclo-, respectively.

A Novel Active Analogue of Gramicidin S with Smaller Ring Size.

A novel active gramicidin S analogue with smaller ring size, cyclo[-δ-Orn(-Val-Pro-d-Phe-H)-Leu-]2, was synthesized and examined the structure-activity relationship. Its analogue showed antibiotic activity against all Gram-positive microorganisms tested, and its activity was 1/2∼1/8 of that of gramicidin S. The present results indicated that both structures of cyclo(-δ-Orn-Leu-)2 and H-d-Phe-Pro-Val sequence play the important role for showing the antibiotic activity.

A Novel Active Analogue of Gramicidin S with Smaller Ring Size

A novel active gramicidin S analogue with smaller ring size, cyclo[-delta-Orn(-Val-Pro-D-Phe-H)-Leu-]2, was synthesized and examined the structure-activity relationship. Its analogue showed antibiotic activity against all Gram-positive microorganisms tested, and its activity was 1/2-1/8 of that of gramicidin S. The present results indicated that both structures of cyclo(-delta-Orn-Leu-)2 and H-D-Phe-Pro-Val sequence play the important role for showing the antibiotic activity.

New Beauveriolides Produced by Amino Acid‐Supplemented Fermentation of Beauveria sp. FO‐6979

AbstractFor Abstract see ChemInform Abstract in Full Text.

Bew Beauveriolides Produced by Amino Acid-supplemented Fermentation of Beauveria sp. FO-6979.

Five new beauveriolides were isolated from the acetone extracts of Beauveria sp. FO-6979 mycelia fermented in amino acid-supplemented media. The structures were elucidated by spectroscopic studies including NMR experiments and chemical degradation. All the beauveriolides are cyclodepsipeptides consisting of one 3-hydroxy-4-methyl fatty acid, two L-amino acids and one D-amino acid in common. Beauveriolide VII with the structure of cyclo-[3-hydroxy-4-methyloctanoyl-L-phenylalanyl-L-alanyl-D-valyl] inhibited lipid droplet formation and cholesteryl ester synthesis in macrophages, but the other beauveriolides showed only slight or almost no effect on lipid droplet formation.

A twenty-four membered mixed-metal macrocycle; synthesis and structure of cyclo-[(3-Me-1,2-C6H3O2)2SbNa(THF)2]6.

The first example of a twenty-four membered mixed p-/s-block macrocycle, cyclo-[(3-Me-1,2-C6H3O2)2SbNa(THF)2]6 1 has been synthesised and structurally characterised from the reaction between 3-Me-1,2-C6H3(OH)(ONa) and (Me2N)2Sb(CH2)3Sb(NMe2)2.

A New Cyclic Pseudopeptide Composed of (l)-Proline and 3-Aminobenzoic Acid Subunits as a Ditopic Receptor for the Simultaneous Complexation of Cations and Anions

The synthesis and receptor properties of a cyclic pseudopeptide composed of (l)-proline and the nonnatural amino acid 3-aminobenzoic acid in an alternating sequence are described. The structure of cyclo[(l)Pro-AB]3 was determined in the solid state by X-ray crystallography and in solution by one- and two-dimensional NMR techniques and FT-IR spectroscopy. The cyclic peptide preferentially adopts conformations comparable with the cone conformation of calixarenes. Similar to calixarenes, cyclo[(l)Pro-AB]3 is able to bind cations by cation−π interactions with its aromatic subunits. In some complexes, the peptide NH groups interact additionally with anions and the cyclic peptide thus behaves as a ditopic receptor. The structure of the ternary complex between cyclo[(l)Pro-AB]3 and N-methylquinuclidinium iodide was determined by X-ray crystallography. Spectroscopic investigations show that this complex has a similar geometry in solution. Stability constants of complexes of the cyclopeptide with various ion pairs...

A Mercuracarborand Characterized by B-Hg-B Bonds: Synthesis and Structure of cyclo-[(t-BuMe2Si)2C2B10H8Hg

A Mercuracarborand Characterized by B-Hg-B Bonds: Synthesis and Structure of cyclo-[(t-BuMe2Si)2C2B10H8Hg

Cyclosporin d hydroperoxide a new metabolite of Tolypocladium terricola

The structure of cyclo(-Xaa 1-Val 2-Sar 3-MeLeu 4-Val 5-MeLeu 6-Ala 7- D-Ala 8-MeLeu 9-MeLeu 10-MeVal 11-) ( 1), where Xaa is 3-hydroxy-7-hydroperoxy-4-methyl-2-methylamino-5 E-octenoic acid was assigned to a new metabolite of the fungus Tolypocladium terricola on the basis of MS and NMR results.

Solution and solid‐state structure of the diketopiperazine of tyrosyl‐tetrahydroisoquinoline‐3‐carboxylic acid

delta-Selective antagonism of [L-Tic2]-peptides, including the simple dipeptide Tyr-L-Tic-NH2, is linked to the Tyr-Tic-"recognition site". In order to gain further information on the conformational preferences of the Tyr-Tic-moiety we have undertaken a structural study of a cyclic analog, the diketopiperazine of Tyr-Tic. A conformational study of cyclo[-Tyr-Tic-], that is almost devoid of opioid activity, can also be useful to discriminate between the role of the two aromatic rings and of the basic nitrogen in determining antagonism. The structure of cyclo[-Tyr-Tic-] has been solved in a DMSO/water solution at 278 K by NMR spectroscopy and in the solid state by X-ray diffraction methods. The two informations are almost identical, with an arrangement of the aromatic rings rather different from that of the putative bioactive conformation of the parent linear dipeptide. This difference points to the importance of conformational effects and is in agreement with the hypothesis that the positive center may be not essential for antagonism.

Conformations of 24-Membered Ring Pseudopeptides Containing N,N′-Ethylene-Bridged Dipeptides Constructed from (S)-Alanine, -Leucine, -Isoleucine, and -Phenylalanine

24-Membered ring pseudopeptides, cyclo[Gly-eXX-Gly]2 {eXX; N,N′-ethylene-bridged dipeptide, X = (S)-alanine(A), -leucine(L), -isoleucine(I), and -phenylalanine(F)} and cyclo[Sar-eXX-Gly]2 {X = (S)-A and -F} were prepared and their conformations were investigated by 1H and 13C NMR spectroscopy in dimethylsulfoxide-d6. It was found from NMR measurements that the major conformers ( ≥90% abundance) of the four cyclo[Gly-eXX-Gly]2 and major ones (≃70%) of the two cyclo[Sar-eXX Gly]2 have C2-symmetric structures, in which all peptide bonds of cyclo[Gly-eXX-Gly]2 (X = A, L, and I) and cyclo[Sar-eAA-Gly]2 are trans, while two Gly-eFF peptide bonds of cyclo[Gly-eFF-Gly]2 and two Sar-eFF ones of cyclo[Sar-eFF-Gly]2 are cis though the other peptide bonds are trans. 13C spin-lattice relaxation times (T1) of all macrocycles showed small contribution of segmental mobility to T1. The structures of cyclo[Gly-eAA-Gly]2 and cyclo[Sar-eAA-Gly]2 were optimized by molecular mechanics on the basis of NMR data.

Crystal structure of cyclo(C-α-methyl-phenylalanine- proline) (S,S)/(R,S) diastereomeric mixture, C15H18N2O2

Crystal structure of cyclo(C-α-methyl-phenylalanine- proline) (S,S)/(R,S) diastereomeric mixture, C₁₅H₁₈N₂O₂

Crystal structure of cyclo(C-α-methyl-phenylalanine-proline) (S,S)/(R,S) diastereomeric mixture, C15H18N2O2

Crystal structure of cyclo(C-<i>α</i>-methyl-phenylalanine-proline) (S,S)/(R,S) diastereomeric mixture, C₁₅H₁₈N₂O₂

Structure of cyclo(-N-hydroxyglycyl-L-phenylalanyl-)

C 11 H 12 N 2 O 3 cristallise dans P2 1 2 1 2 1 avec a=14,523, b=11,622, c=6,293 A, Z=4; affinement jusqu'a R=0,055. Geometrie moleculaire. Les molecules s'empilent le long de l'axe a

Structure of cyclo(-N-hydroxyglycyl-L-alanyl-)

C 5 H 8 N 2 O 3 cristallise dans P2 1 2 1 2 1 avec a=18,081, b=7,760 et c=4,615 A, Z=4; affinement jusqu'a R=0,042. Le cycle dicetopiperazine adopte une conformation presque plane. Il y a deux sortes de liaisons hydrogene O 3 −H...O 2 (3/2-x, 1-y, 1/2+z) 2,599 A et N 2 -H...O 1 (2-x, -1/2+y, 5/2-z) 2,878 A

Structure ofcyclo(-L-phenylalanyl-N-methyl-L-α-aminobutyryl-)

Structure of<i>cyclo</i>(-<scp>L</scp>-phenylalanyl-<i>N</i>-methyl-<scp>L</scp>-α-aminobutyryl-)

Structure of cyclo(-L-phenylalanyl-L-phenylalanyl-)

Bis (phenylmethyl)-2,5-piperazinedione, CIsH~sN202, Mr=294.3, orthorhombic, P22~21, a =6.181(1), b=10.380(3), c=23.795(4)A, V= 1526.8 (6) A 3, z = 4, D x = 1.28 g cm -3, 2(Cu Ka) = 1.54178 A, # = 6-0 cm -~, F(000) = 624, room tem- perature, R = 0.056 for 959 observed reflections and 176 variables. The 2,5-piperazinedione ring has a flattened boat conformation with the C~ atoms in pseudoaxial positions. One of the phenylalanyl residues faces the 2,5-piperazinedione ring (X~ = 69.0 (6)°), the other is in an extended conformation (X~ = -61.9 (6)°). The 09 torsion angles in both cis peptide units are small and equal to -0.9 (7) and 0.1 (7) °. Introduction. The preference for an aromatic part of an amino-acid residue to fold over the 2,5-piperazinedione (hereafter DKP) skeleton is a well known phenomenon. The folded conformation has been observed both in the solid state and in solution. However, for cis cyclic dipeptides built up of two aromatic amino-acid residues, steric repulsions prevent the molecule from adopting a conformation in which both aromatic rings fold over

Cyclic peptides

Cyclochlorotine (CCT) is a toxic metabolite of Penicillium islandicum Sopp, having the structure of cyclo(‐L‐Ser‐L‐β‐Phe‐L‐Ser‐L‐Pro(Cl2)‐L‐Abu‐). An analog of CCT, cyclo(‐L‐Ser‐L‐β‐Phe‐L‐Ser‐L‐Pro(Cl)‐L‐Abu‐) ([L‐Pro(Cl)4]CCT, 1), has been synthesized by the conventional method for peptide synthesis in order to study possible toxic activity of 1. Peptide 1 showed no toxicity toward several microorganisms and mice. 1H‐N.m.r. and CD studies on 1 indicate that the conformation of 1 in solution is similar to that of crystalline CCT. These results suggest that 3‐cis‐chlorine moiety of Pro(Cl2) in CCT plays an essential role in biological activities.