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Pyrrolidine Ring (pyrrolidine + ring)

Distribution by Scientific Domains
Chemistry93%
Distribution within Chemistry
Organic Chemistry26%
General & Introductory Chemistry19%

Selected Abstracts

ChemInform Abstract: A New Synthetic Methodology for the Pyrrolidine Ring.

CHEMINFORM, Issue 31 2010
Dalila Belei
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Discovery of New Diphenyloxazole Derivatives Containing a Pyrrolidine Ring: Orally Active Prostacyclin Mimetics.

CHEMINFORM, Issue 43 2005
Part 2.
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

The First Fulleropyrrolidine Derivative of Sc3N@C80: Pronounced Chemical Shift Differences of the Geminal Protons on the Pyrrolidine Ring.

CHEMINFORM, Issue 41 2005
Claudia M. Cardona
No abstract is available for this article. [source]

Redox Active Two-Component Films of Palladium and Covalently Linked Zinc Porphyrin,Fullerene Dyad

ELECTROANALYSIS, Issue 9 2006
Marta Plonska
Abstract Redox active films have been generated electrochemically by the reduction of dyads consisting of fullerene C60 covalently linked to zinc meso -tetraphenyloporphyrin, ZnPC60, and palladium acetate. The films are believed to consist of a polymeric network formed via covalent bonds between the palladium atoms and the fullerene moieties. In these films, the zinc porphyrin moiety is covalently linked to the polymeric chains through the pyrrolidine ring of the fullerene. The ZnPC60/Pt films are electrochemically active in both positive and negative potential excursions. At positive potentials, two oxidation steps for the zinc porphyrin are observed. In the negative potential range, electron transfer processes involving the zinc porphyrin and the fullerene entities are observed. Film formation is also accompanied by palladium deposition on the electrode surface. The presence of a metallic phase in the film influences its morphology, structure and electrochemical properties. [source]

Transition States of the Asymmetric Michael Reactions of Aldehydes Catalyzed by Trimethylsilyl-Protected Diphenylprolinol

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2009
Jian-Qiang Zhao
Abstract The asymmetric Michael reactions of aldehydes and nitroalkenes catalyzed by trimethylsilyl-protected diphenylprolinol were investigated by using density functional theory calculations. As a result of the stereospecific blockade of the bulky diphenylsiloxymethyl group on the pyrrolidine ring, the Re face of the enamine double bond is effectively shielded. For acetaldehyde, there are two different conformers of the enamine intermediate. On the basis of the two conformers of the enamine intermediate, four different reaction pathways were considered and four different transition states were searched for the enantioselective asymmetric Michael reaction of acetaldehyde and nitroalkene. The lowest- and second-lowest-energy transition states are both formed via the same intermediate IM2. The enantiomeric excess, calculated to be 96,%,ee, is in good agreement with the experimental value. For propanal, on the basis of the four different conformers of the prolinol,enamine intermediate, eight different reaction pathways were considered and eight transition states were searched for the enantioselective asymmetric Michael reaction. The calculated ee value is 99.5,%, which is in good agreement with the experimental ee value of 99,%. The lowest- and second-lowest-energy transition states are formed via different enamine intermediates, which is different from the case of acetaldehyde. The calculations also reveal that the intermediates play an important role in the reactions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Structures of the Reactive Intermediates in Organocatalysis with Diarylprolinol Ethers

HELVETICA CHIMICA ACTA, Issue 7 2009

Abstract Structures of the reactive intermediates (enamines and iminium ions) of organocatalysis with diarylprolinol derivatives have been determined. To this end, diarylprolinol methyl and silyl ethers, 1, and aldehydes, PhCH2CHO, tBuCH2CHO, PhCH=CHCHO, are condensed to the corresponding enamines, A and 3 (Scheme,2), and cinnamoylidene iminium salts, B and 4 (Scheme,3). These are isolated and fully characterized by melting/decomposition points, [,]D, elemental analysis, IR and NMR spectroscopy, and high-resolution mass spectrometry (HR-MS). Salts with BF4, PF6, SbF6, and the weakly coordinating Al[OC(CF3)3]4 anion were prepared. X-Ray crystal structures of an enamine and of six iminium salts have been obtained and are described herein (Figs.,2 and 4,8, and Tables,2 and 7) and in a previous preliminary communication (Helv. Chim. Acta2008, 91, 1999). According to the NMR spectra (in CDCl3, (D6)DMSO, (D6)acetone, or CD3OD; Table,1), the major isomers 4 of the iminium salts have (E)-configuration of the exocyclic NC(1,) bond, but there are up to 11% of the (Z)-isomer present in these solutions (Fig.,1). In all crystal structures, the iminium ions have (E)-configuration, and the conformation around the exocyclic N-CC-O bond is synclinal-exo (cf.C and L), with one of the phenyl groups over the pyrrolidine ring, and the RO group over the , -system. One of the meta -substituents (Me in 4b, CF3 in 4c and 4e) on a 3,5-disubstituted phenyl group is also located in the space above the , -system. DFT Calculations at various levels of theory (Tables,3,6) confirm that the experimentally determined structures (cf. Fig.,10) are by far (up to 8.3,kcal/mol) the most stable ones. Implications of the results with respect to the mechanism of organocatalysis by diarylprolinol derivatives are discussed. [source]

Are Oxazolidinones Really Unproductive, Parasitic Species in Proline Catalysis?

HELVETICA CHIMICA ACTA, Issue 3 2007
Experiments Pointing to an Alternative View, Thoughts
Abstract The N,O-acetal and N,O-ketal derivatives (oxazolidinones) formed from proline, and aldehydes or ketones are well-known today, and they are detectable in reaction mixtures involving proline catalysis, where they have been considered ,parasitic dead ends'. We disclose results of experiments performed in the early 1970's, and we describe more recent findings about the isolation, characterization, and reactions of the oxazolidinone derived from proline and cyclohexanone. This oxazolidinone reacts (THF, room temperature) with the electrophiles , -nitrostyrene and chloral (=trichloroacetaldehyde), to give the Michael and aldol adduct, respectively, after aqueous workup (Scheme,5). The reactions occur even at ,75° when catalyzed with bases such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or EtN(i-Pr)2 (DIPEA) (10%; Table,1). It is shown by NMR (Figs.,1 and 3) and IR analysis (Figs.,2 and 4) that the primarily detectable product (before hydrolysis) of the reaction with the nitro-olefin is again an oxazolidinone. When dissolved in hydroxylic solvents such as MeOH, ,hexafluoroisopropanol' ((CF3)2CHOH; HFIP), AcOH, CF3COOH, or in LiBr-saturated THF, the ring of the oxazolidinone from cyclohexanone and proline opens up to the corresponding iminium ion (Tables,2,4), and when treated with strong bases such as DBU (in (D8)THF) the enamino-carboxylate derived from proline and cyclohexanone is formed (Scheme,8). Thus, the two hitherto putative participants (iminium ion and enamine) of the catalytic cycle (Scheme,9) have been characterized for the first time. The commonly accepted mechanism of the stereoselective C,C- or C,X-bond-forming step (i.e., A,D) of this cycle is discussed and challenged by thoughts about an alternative model with a pivotal role of oxazolidinones in the regio- and diastereoselective formation of the intermediate enamino acid (by elimination) and in the subsequent reaction with an electrophile (by trans -addition with lactonization; Schemes,11,14). The stereochemical bias between endo - and exo -space of the bicyclo[3.3.0]octane-type oxazolidinone structure (Figs.,5 and 6) is considered to possibly be decisive for the stereochemical course of events. Finally, the remarkable consistency, with which the diastereotopic Re -face of the double bond of pyrrolidino-enamines (derived from proline) is attacked by electrophiles (Schemes,1 and 15), and the likewise consistent reversal to the Si -face with bulky (Aryl)2C-substituents on the pyrrolidine ring (Scheme,16) are discussed by invoking stereoelectronic assistance from the lone pair of pyramidalized enamine N-atoms. [source]

Quantum mechanical study of the conformational behavior of proline and 4R-hydroxyproline dipeptide analogues in vacuum and in aqueous solution

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2002
Caterina Benzi
The conformational behavior of the title compounds has been investigated by Hartree,Fock, MP2, and DFT computations on the most significant structures related to variations of the backbone dihedral angles, cis/trans isomerism around the peptide bond, and diastereoisomeric puckering of the pyrrolidine ring. In vacuum the reversed , turn (,l), characterized by an intramolecular hydrogen bridge, corresponds to the absolute energy minimum for both puckerings (up and down) of the pyrrolidine ring. An additional energy minimum is found in the helix region, but only for an up puckering of the pyrrolidine ring. When solvent effects are included by means of the polarizable continuum model the conformer observed experimentally in condensed phases becomes the absolute minimum. The down puckering is always favored over its up counterpart, albeit by different amounts (0.4,0.5 kcal/mol for helical structures and about 2 kcal/mol for ,l structures). In helical structures cis arrangements of the peptide bond are only slightly less stable than their trans counterparts. This is no longer true for ,l structures, because the formation of an intramolecular hydrogen bond is possible only for trans peptide bonds. In most cases, proline and hydroxyproline show the same general trends; however, the electronegative 4(R) substituent of hydroxyproline leads to a strong preference for up puckerings irrespective of the backbone conformation. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 341,350, 2002 [source]

4-Fluoroproline derivative peptides: effect on PPII conformation and SH3 affinity

JOURNAL OF PEPTIDE SCIENCE, Issue 7 2006
Paolo Ruzza
Abstract Eukaryotic signal transduction involves the assembly of transient protein,protein complexes mediated by modular interaction domains. Specific Pro-rich sequences with the consensus core motif PxxP adopt the PPII helix conformation upon binding to SH3 domains. For short Pro-rich peptides, little or no ordered secondary structure is usually observed before binding interactions. The association of a Pro-rich peptide with the SH3 domain involves unfavorable binding entropy due to the loss of rotational freedom on forming the PPII helix. With the aim of stabilizing the PPII helix conformation in the Pro-rich HPK1 decapeptide PPPLPPKPKF (P2), a series of P2 analogues was prepared, in which specific Pro positions were alternatively occupied by 4(S)- or 4(R)-4-fluoro- L -proline. The interactions of these peptides with the SH3 domain of the HPK1-binding partner HS1 were quantitatively analyzed by the NILIA-CD approach. A CD thermal analysis of the P2 analogues was performed to assess their propensity to adopt the PPII helix conformation. Contrary to our expectations, the Kd values of the analogues were lower than that of the parent peptide P2. These results clearly show that the induction of a stable PPII helix conformation in short Pro-rich peptides is not sufficient to increase their affinity toward the SH3 domain and that the effect of 4-fluoroproline strongly depends on the position of this residue in the sequence and the chirality of the substituent in the pyrrolidine ring. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd. [source]

Collagen-like triple helix formation of synthetic (Pro-Pro-Gly)10 analogues: (4(S)-hydroxyprolyl-4(R)-hydroxyprolyl-Gly)10, (4(R)-hydroxyprolyl-4(R)-hydroxyprolyl-Gly)10 and (4(S)-fluoroprolyl-4(R)-fluoroprolyl-Gly)10

JOURNAL OF PEPTIDE SCIENCE, Issue 10 2005
Masamitsu Doi
Abstract For the rational design of a stable collagen triple helix according to the conventional rule that the pyrrolidine puckerings of Pro, 4-hydroxyproline (Hyp) and 4-fluoroproline (fPro) should be down at the X-position and up at the Y-position in the X-Y-Gly repeated sequence for enhancing the triple helix propensities of collagen model peptides, a series of peptides were prepared in which X- and Y-positions were altogether occupied by HypR, HypS, fProR or fProS. Contrary to our presumption that inducing the X-Y residues to adopt a down-up conformation would result in an increase in the thermal stability of peptides, the triple helices of (HypS -HypR -Gly)10 and (fProS -fProR -Gly)10 were less stable than those of (Pro-HypR -Gly)10 and (Pro-fProR -Gly)10, respectively. As reported by Bächinger's and Zagari's groups, (HypR -HypR -Gly)10 which could have an up-up conformation unfavorable for the triple helix, formed a triple helix that has a high thermal stability close to that of (Pro-HypR -Gly)10. These results clearly show that the empirical rule based on the conformational preference of pyrrolidine ring at each of X and Y residues should not be regarded as still valid, at least for predicting the stability of collagen models in which both X and Y residues have electronegative groups at the 4-position. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd. [source]

Vibrational spectral studies and the non-linear optical properties of a novel NLO material L -prolinium tartrate

JOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2006
L. Padmaja
Abstract Vibrational spectral analysis of the novel non-linear optical (NLO) material, L -prolinium tartrate (LPT) was carried out using NIR-FT-Raman and FT-IR spectroscopy. The density functional theoretical (DFT) computations have been performed at B3LYP/6,31G (d) level to derive equilibrium geometry, vibrational wavenumbers, intensities and first hyperpolarizability. The reasonable NLO efficiency, predicted for the first time in this novel compound, has been confirmed by Kurtz,Perry powder second-harmonic generation (SHG) experiments. The charge-transfer interaction between the pyrrolidine ring and the carbonyl group of the tartrate anion through the intramolecular ionic hydrogen bonds is confirmed by the simultaneous activation of ring modes in IR and Raman spectra. The splitting of the ring-breathing mode, pseudo-rotational ring puckering modes and the NH2 modes of the pyrrolidine ring lead to the conclusion that the pyrrolidine ring adopts a conformation intermediate between the envelope (bent) form and the half-chair (twisted) form, resulting in the lowering of symmetry from C2 to Cs. The lowering of the methylenic stretching wavenumbers and the enhancement of the stretching intensities suggest the existence of the electronic effects of back-donation in LPT. The positional disorder of the pyrrolidine ring, the presence of blue-shifting H-bonds as well as other non-bonded interactions in LPT, low frequency H-bond vibrations and the role of intramolecular charge transfer and the hydrogen bonds in making the molecule NLO active have been analysed on the basis of the vibrational spectral features. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Synthesis and Photoresponsive Properties of Optically Active Methacrylic Polymers Bearing Side-Chain Azocarbazole Moieties

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2009
Luigi Angiolini
Abstract The synthesis of a novel optically active methacrylic monomer containing in the side chain the (S)-3-hydroxy- N -phenyl pyrrolidine ring linked to a 4-cyanophenylazocarbazole moiety [(S)- MCAPP - C] and of the analogous achiral monomer (MCAPE-C) is described. Both the monomers have been radically polymerized to produce the corresponding homopolymers as well as the copolymer at 50% molar composition. The photoinduction of birefringence has been assessed on thin films of the polymeric materials in order to evaluate their behavior as materials for optical data storage. Surface relief gratings (SRG) can also be inscribed over the material. The results are interpreted in terms of different cooperative performance and conformational stiffness of the chromophoric co-units in the polymeric derivatives. [source]

5-Amino-4-(4-diethyl­amino­phenyl)-2-(4-hydroxy­phenyl)-7-(pyrrolidin-1-yl)-1,6-naphthyridine-8-carbo­nitrile

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2001
R. Sankaranarayanan
In the title compound, C29H30N6O, the naphthyridine moiety is planar with a dihedral angle between the fused rings of 1.9,(1)°. The phenol ring is nearly coplanar, while the diethyl­amino­phenyl substituent is orthogonal to the central naphthyridine ring and the pyrrolidine ring makes an angle of 11.2,(1)° with it. The O atom of the hydroxy substituent is coplanar with the phenyl ring to which it is attached. The molecular structure is stabilized by a C,H,N-type intramolecular hydrogen bond and the packing is stabilized by intermolecular C,H,,, O,H,N and N,H,O hydrogen bonds. [source]

Novel l,-Methylcarbapenems Having Cyclic Sulfonamide Moieties: Synthesis and Evaluation of in-vitro Biological Activity , Part II

ARCHIV DER PHARMAZIE, Issue 9 2009
Seong Jong Kim
Abstract The synthesis of a new series of 1,-methylcarbapenems having cyclic sulfonamide moieties is described. Their in-vitro antibacterial activities against both Gram-positive and Gram-negative bacteria were tested and the effect of a substituent on the pyrrolidine ring was investigated. One particular compound IIIe having a [1,2,5]thiadiazolidin 1,1-dioxide moiety showed the most potent antibacterial activity. [source]

Two Regioisomers of Endohedral Pyrrolidinodimetallofullerenes M2@Ih -C80(CH2)2NTrt (M=La, Ce; Trt=trityl): Control of Metal Atom Positions by Addition Positions

CHEMISTRY - A EUROPEAN JOURNAL, Issue 40 2009
Michio Yamada Dr.
Abstract The two regioisomers of endohedral pyrrolidinodimetallofullerenes M2@Ih -C80(CH2)2NTrt (M=La, Ce; Trt=trityl) were synthesized, isolated, and characterized. X-ray crystallographic analyses of [6,6]-La2@Ih -C80(CH2)2NTrt and [6,6]-Ce2@Ih -C80(CH2)2NTrt revealed that the encapsulated metal atoms are located at the slantwise positions on the mirror plane that parallels the pyrrolidine ring. Paramagnetic NMR analyses of [6,6]- and [5,6]-Ce2@Ih -C80(CH2)2NTrt were also carried out to clarify the metal positions. As for the [6,6]-adduct, the metal positions obtained by paramagnetic NMR analysis agree well with the X-ray structure. In contrast, paramagnetic NMR analysis of the [5,6]-adduct showed that the two Ce atoms are collinear with the pyrrolidine ring. We also compared the observed paramagnetic effects of the pyrrolidinodimetallofullerenes with those of other cerium-encapsulating fullerene derivatives such as bis-silylated Ce2@Ih -C80 and a carbene adduct of Ce2@Ih -C80. We found that the metal positions can be explained by the electrostatic potential maps of the corresponding [6,6]- and [5,6]-adducts of [Ih -C80(CH2)2NTrt]6,. These findings clearly show that metal positions inside fullerene cages can be controlled by means of the addition positions of the addends. In addition, the radical anions of the pyrrolidinodimetallofullerenes were prepared by bulk controlled-potential electrolysis and characterized by X-band EPR spectral study. [source]

Conformations of three heterocyclic perhydro­pyrrolobenzofurans and polymeric assembly via co-operative inter­molecular C,H,O hydrogen bonds

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2006
H. S. Yathirajan
In 1-cyclo­hexyl-6,6,8a-trimethyl-3a,6,7,8a-tetra­hydro-1H -1-benzofuro[2,3- b]pyrrole-2,4(3H,5H)-dione, C19H27NO3, (I), and the isomorphous compounds 6,6,8a-trimethyl-1-phenyl-3a,6,7,8a-tetra­hydro-1H -1-benzofuro[2,3- b]pyrrole-2,4(3H,5H)-dione, C19H21NO3, (II), and 6,6,8a-trimethyl-1-(3-pyridyl)-3a,6,7,8a-tetra­hydro-1H -1-benzofuro[2,3- b]pyrrole-2,4(3H,5H)-dione, C18H20N2O3, (III), the tetra­hydro­benzo,dihydro­furo,pyrrolidine ring systems are folded at the cis junction of the five-membered rings, giving rise to a non-planar shape of the tricyclic cores. The dihydro­furan and pyrrolidine rings in (I) are puckered and adopt an envelope conformation. The cyclo­hexene rings adopt a half-chair conformation in all the mol­ecules, while the substituent N -cyclo­hexyl ring in (I) assumes a chair form. Short intra­molecular C,H,O contacts form S(5) and S(6) motifs. The isomorphous compounds (II) and (III) are effectively isostructural, and aggregate into chains via inter­molecular C,H,O hydrogen bonds. [source]