Structural characteristics of the carboxylic ester group

Schweizer, W. Bernd; Dunitz, J.D.

doi:10.1107/s0108767381097092

Cited by 14 publications

(14 citation statements)

References 3 publications

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“…Bond lengths and bond angles are in general agreement with previously reported values for the geometry of the tert-butyloxycarbonylamino [31] and methyl ester [32] groups, the peptide unit [33,34], and the fluorenyl moiety [35,36]. In particular, the (sp 2 )C-C(sp 2 ) bond, directly connecting the two phenyl rings (in the range 1.47-1.48 Å ) is typi- cal of a biphenyl system, and the two (sp 3 …”

Section: Crystal-state Conformational Analysissupporting

confidence: 85%

“…The side-chain The C-terminal Gly residue of the dipeptide is found in the bridge region of the conformational space [40] with , values of −79.2(4)°, 1.2(5)°for molecule A and 83.1(5)°, −3.2(6)°for molecule B. In the four molecules of the two compounds: (i) the ester -C( O)-O-bonds [32] are trans, with a deviation from planarity not exceeding 3°; (ii) the peptide bond [33,34] (in Boc-Afc-Gly-OMe) is distorted trans planar, the 1 torsion angle being 164.5(3)°for molecule A and −169.9(3)°for molecule B; (iii) the urethane C( O)-NH-bond [31] is trans in Boc-AfcOMe, with 0 173.3(2)°for molecule A and 176.2(2)°f or molecule B. However, this bond is cis in Boc-AfcGly-OMe, with 0 0.1(5)°for molecule A and −1.2(6)°for molecule B; (iv) the q 1 torsion angle of the tert-butyloxycarbonylamino group [31] is trans planar, with a deviation of less than 10°from 180°; (v) the ester conformation with respect to the preceding C h -N bond [41] is synperiplanar in the amino acid derivative, but it is antiperiplanar in the dipeptide.…”

Section: Crystal-state Conformational Analysismentioning

confidence: 99%

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Synthesis, conformational study, and spectroscopic characterization of the cyclic Cα,α-disubstituted glycine 9-amino-9-fluorenecarboxylic acid

et al. 1999

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A series of terminally blocked peptides (to the pentamer level) from L-Ala and the cyclic C alpha, alpha-disubstituted Gly residue Afc and one Gly/Afc dipeptide have been synthesized by solution method and fully characterized. The molecular structure of the amino acid derivative Boc-Afc-OMe and the dipeptide Boc-Afc-Gly-OMe were determined in the crystal state by X-ray diffraction. In addition, the preferred conformation of all of the model peptides was assessed in deuterochloroform solution by FT-IR absorption and 1H-NMR. The experimental data favour the conclusion that the Afc residue tends to adopt either the fully-extended (C5) or a folded/helical structure. In particular, the former conformation is highly populated in solution and is also that found in the crystal state in the two compounds investigated. A comparison with the structural propensities of the strictly related C alpha, alpha-disubstituted Gly residues Ac5c and D phi g is made and the implications for the use of the Afc residue in conformationally constrained analogues of bioactive peptides are briefly examined. A spectroscopic (UV absorption, fluorescence, CD) characterization of this novel aromatic C alpha, alpha-disubstituted Gly residue is also reported.

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Section: Crystal-state Conformational Analysissupporting

confidence: 85%

Section: Crystal-state Conformational Analysismentioning

confidence: 99%

Synthesis, conformational study, and spectroscopic characterization of the cyclic Cα,α-disubstituted glycine 9-amino-9-fluorenecarboxylic acid

et al. 1999

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“…Esters, 52 amides 53 and their analogs, ureas, and carbamates are well-studied systems common in medicinal chemistry. They have a very strong preference to adopt planar conformations due to resonance stabilization.…”

Section: Simple Acyclic Systemsmentioning

confidence: 99%

Small Molecule Conformational Preferences Derived from Crystal Structure Data. A Medicinal Chemistry Focused Analysis

Brameld

Kuhn

Reuter

et al. 2008

J. Chem. Inf. Model.

340

332

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Based on torsion angle distributions of frequently occurring substructures, conformation preferences of druglike molecules are presented, accompanied by a review of the relevant literature. First, the relevance of the Cambridge Structural Database (CSD) for drug design is demonstrated by comparing substructures present in compounds entering clinical trials with those found in the CSD and protein-bound ligands in the Protein Data Bank (PDB). Next, we briefly highlight preferred conformations of elementary acyclic systems, followed by a discussion of sulfonamide conformations. Due to their central role in medicinal chemistry, we discuss properties of aryl ring substituents in depth, including biaryl systems and systems of two aryl rings connected by two acyclic bonds. For a subset of torsion motifs, we also compare torsion angle histograms derived from CSD structures with those derived from ligands in the PDB. Furthermore, selected properties of some six-and seven-membered ring systems are discussed. The article closes with a section on attractive sulfuroxygen contacts.

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“…Bond lengths and angles of the three Compounds compare well with each other and with those found in other /;BrBz-NH (Hamelin et al, 1982;Nakamura et al, 1973;Robert et ai., 1984;Toniolo et al, 1985Toniolo et al, ,1986Chakrabarti and Dunitz, 1982) and Aib-derivatives (Paterson et al, 1981), oxazolones and esters (Nair and Vijayan, 1980;Schweizer and Dunitz, 1982;Toniolo et al, 1983b;Norskov-Lauritsen et al, 1985). In particular, we note that:…”

Section: Resultsmentioning

confidence: 96%

Crystal structures of N-parabromobenzoyl-α-aminoisobutyric acid and two derivatives

Valle¹,

Crisma²,

Toniolo³

1986

Zeitschrift Für Kristallographie - Crystalline Materials

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The crystal structures of N-para-bromobenzoyl-ot-aminoisobutyric acid (1), and its S(4H)-oxazolone (2) and methyl ester (3) derivatives have been determined by X-ray difTraction techniques. The Compounds possess the foUowing parameters: (1) monocUnic, space group Plija, a = 10.057(4), b = 12.733(4), c = 9.706(4) k, ß = 99.8(3)°, and Z = 4; (2) monocUnic, P2,/fl, a = 12.637(4), b = 7.818(3), c = 12.241(4) A, /? = 110.7(2)°, and Z = 4;(3)orthorhombicPca6,a = 17.615(5),Ä = 14.357(5), c = 10.251(4) Ä, Z = 8. The crystal structures were solved by direct methods. The least-squares refinements led Xo.R values of0.067,0.047 and 0.048 for 1205, 1510 and 734 reflections with / > 3 ff(I) for 1-3, respectively. The conformation of Compounds (1) and (3) is remarkably simülar, with a trans amide bond and folding about the N-aC bond. The C=N bond of the oxazolone group of Compound (2) is not conjugated with the ester moiety.

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Structural characteristics of the carboxylic ester group

Cited by 14 publications

References 3 publications

Synthesis, conformational study, and spectroscopic characterization of the cyclic Cα,α-disubstituted glycine 9-amino-9-fluorenecarboxylic acid

Synthesis, conformational study, and spectroscopic characterization of the cyclic Cα,α-disubstituted glycine 9-amino-9-fluorenecarboxylic acid

Small Molecule Conformational Preferences Derived from Crystal Structure Data. A Medicinal Chemistry Focused Analysis

Crystal structures of N-parabromobenzoyl-α-aminoisobutyric acid and two derivatives

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