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Volumn 74, Issue 17, 2009, Pages 6511-6525

Characterization of the two fundamental conformations of benzoylureas and elucidation of the factors that facilitate their conformational interchange

Author keywords

[No Author keywords available]

Indexed keywords

COMPUTATIONAL ANALYSIS; CONFORMATIONAL BEHAVIOR; ELECTRONIC EFFECTS; HYDROGEN BONDINGS; INTRAMOLECULAR HYDROGEN BOND; REFERENCE SOURCE; SWITCH CONFORMATIONS;

EID: 69549085003     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo900871a     Document Type: Article
Times cited : (28)

References (86)
  • 6
    • 33646007243 scopus 로고    scopus 로고
    • McDonough, S. I., Ed.; Kluwer/Academic/Plenum Press: New York
    • Norton, R. S.; Baell, J. B.; Angus, J. A. In Calcium channel pharmacology; McDonough, S. I., Ed.; Kluwer/Academic/Plenum Press: New York, 2003; pp 143-179.
    • (2003) Calcium Channel Pharmacology , pp. 143-179
    • Norton, R.S.1    Baell, J.B.2    Angus, J.A.3
  • 9
    • 0003670390 scopus 로고    scopus 로고
    • Moreover, benzoylureas have a good track record in marketed pharmaceuticals. For example, see: Meister Media Worldwide, Willoughby, OH
    • Moreover, benzoylureas have a good track record in marketed pharmaceuticals. For example, see: Ware, G.; Whitcare, D. The Pesticide Book, 6th ed.; Meister Media Worldwide, Willoughby, OH, 2004.
    • (2004) The Pesticide Book, 6th Ed.
    • Ware, G.1    Whitcare, D.2
  • 15
    • 36549056638 scopus 로고    scopus 로고
    • L-binding, α helical mimetics was presented in part at the 20th Royal Australian Chemical institute Organic Chemistry Conference, Cairns, Australia, 2004, abstract P(RACIOC) 40 and at Connect 2005, Sydney, Australia, 2005, Abstracts 248 and 364. The worldwide patent disclosing these structures was published in 2006 (Lessene G.; Baell, J. B. α-Helical Mimetics, PCT/AU2005/000968). This system has apparently been "rediscovered" in the interim and published
    • L-binding, α helical mimetics was presented in part at the 20th Royal Australian Chemical institute Organic Chemistry Conference, Cairns, Australia, 2004, abstract P(RACIOC) 40 and at Connect 2005, Sydney, Australia, 2005, Abstracts 248 and 364. The worldwide patent disclosing these structures was published in 2006 (Lessene G.; Baell, J. B. α-Helical Mimetics, PCT/AU2005/000968). This system has apparently been "rediscovered" in the interim and published (Rodriguez, J. M.; Hamilton, A. D. Angew. Chem., Int. Ed. 2007, 46, 8614-8617.
    • (2007) Angew. Chem., Int. Ed. , vol.46 , pp. 8614-8617
    • Rodriguez, J.M.1    Hamilton, A.D.2
  • 17
    • 69549143025 scopus 로고    scopus 로고
    • note
    • Of 25 structures in version 5.30 of CCD, three were in this alternative conformation.
  • 18
    • 0035811453 scopus 로고    scopus 로고
    • Maximin2 using the Tripos Forcefield as implemented in Sybyl7.01 (Tripos Associates, MO); a third, extended (EEZ) form has been identified as a putative biologically active conformation using the Catalyst/HIPHOP software program but in light of the likely generic inability of molecular mechanics to properly analyse benzoylurea conformation, this finding is questionable see
    • Maximin2 using the Tripos Forcefield as implemented in Sybyl7.01 (Tripos Associates, MO); a third, extended (EEZ) form has been identified as a putative biologically active conformation using the Catalyst/HIPHOP software program but in light of the likely generic inability of molecular mechanics to properly analyse benzoylurea conformation, this finding is questionable (see: Kurogi, Y.; Miyata, K.; Okamura, T.; Hashimoto, K.; Tsutsumi, K.; Nasu, M.; Moriyasu, M. J. Med. Chem. 2001, 44, 2304-2307).
    • (2001) J. Med. Chem. , vol.44 , pp. 2304-2307
    • Kurogi, Y.1    Miyata, K.2    Okamura, T.3    Hashimoto, K.4    Tsutsumi, K.5    Nasu, M.6    Moriyasu, M.7
  • 20
    • 37049090155 scopus 로고
    • and analyzed a twisted form of an alkylacylurea but have not extended this to an understanding of conversion between these two forms
    • and analyzed a twisted form of an alkylacylurea (Kohmoto, S.; Kasimura, H.; Nishio, T.; Iida, I.; Kishikawa, K.; Yamamoto, M.; Yamada, K. J. Chem. Soc., Perkin Trans. 2 1994, 1565-1568) but have not extended this to an understanding of conversion between these two forms.
    • (1994) J. Chem. Soc., Perkin Trans. 2 , pp. 1565-1568
    • Kohmoto, S.1    Kasimura, H.2    Nishio, T.3    Iida, I.4    Kishikawa, K.5    Yamamoto, M.6    Yamada, K.7
  • 24
    • 69549094840 scopus 로고    scopus 로고
    • note
    • All classes are drawn as extended, conformationally "neutral" forms, indicative of neither the closed nor twisted conformations.
  • 28
    • 69549093983 scopus 로고    scopus 로고
    • Cooper, R. D. G.; Herron, D. K. Eli Lilly Co.: France, 1975
    • Cooper, R. D. G.; Herron, D. K. Eli Lilly Co.: France, 1975.
  • 32
    • 0001773390 scopus 로고
    • Allinger, N. L., Eliel, E. L., Eds.; John Wiley & Sons: New York
    • Aaron, H. S. In Topics in Stereochemistry; Allinger, N. L., Eliel, E. L., Eds.; John Wiley & Sons: New York, 1979; Vol.11, pp 1-52.
    • (1979) Topics in Stereochemistry , vol.11 , pp. 1-52
    • Aaron, H.S.1
  • 35
    • 69549146636 scopus 로고    scopus 로고
    • note
    • Analogous arguments apply to OH, SH, and amino NH groups, but our focus here is the amide NH.
  • 40
    • 69549153139 scopus 로고    scopus 로고
    • note
    • A slow rate of deuterium exchange is also often used to indicate internal hydrogen bonding. In peptides and proteins, a slow rate of exchange indicates a buried proton, which may or may not be intramolecularly hydrogen bonded (but would usually be expected to be so), or a solvent-exposed proton that is intramolecularly hydrogen bonded. A faster rate of exchange indicates a solvent-exposed and non-hydrogen-bonded proton. In principle, these experiments could be informative for small molecules where solvent exposure is not an issue, and whether an NH proton is hydrogen-bonded or not can be judged by the rate of deuterium exchange. However, these experiments can be tedious to perform and results hard to interpret where rapid equilibria between hydrogen-bonded and non-hydrogen-bonded conformations on an NMR time scale occur, either for a peptide or small molecule.
  • 44
    • 69549144532 scopus 로고    scopus 로고
    • note
    • This supposition is supported by the fact that the data we obtain for benzoylureas are consistent with interpretation v and vi in Table 1.
  • 50
    • 69549155179 scopus 로고    scopus 로고
    • note
    • Selection of model compounds that accurately represent the two extreme states is not necessarily trivial (see, for example, ref 41).
  • 52
    • 69549099596 scopus 로고    scopus 로고
    • note
    • 3 has by protonating the carbonyl group.
  • 53
    • 69549142244 scopus 로고    scopus 로고
    • note
    • 3 is very weak through participation by a poor hydrogen bond acceptor, this situation could give rise to a downfield shift when the solvent is changed to DMSO.
  • 54
    • 69549142245 scopus 로고    scopus 로고
    • note
    • Hence, 5a is a model for noninternally hydrogen-bonded conformations of 1 and 3, 5b is a model for noninternally hydrogen-bonded conformations of 2a and 4a, 5c is a model for noninternally hydrogen-bonded conformations of 2b and 4b, and 5d is a model for noninternally hydrogen-bonded conformations of 2c and 4c.
  • 55
    • 69549142243 scopus 로고    scopus 로고
    • note
    • Several different model systems for internally hydrogen-bonded and noninternally hydrogen-bonded conformations of benzoylureas were investigated before finally choosing the most representative models used herein.
  • 56
    • 69549154038 scopus 로고    scopus 로고
    • note
    • We have made several other class I compounds and have found that all behave similarly (data not shown).
  • 57
    • 69549148975 scopus 로고    scopus 로고
    • note
    • 1 carbonyl.
  • 59
    • 69549155180 scopus 로고    scopus 로고
    • note
    • We have synthesized other class III compounds, and all behave similarly (data not shown).
  • 61
    • 69549156138 scopus 로고    scopus 로고
    • note
    • There are no examples of class III benzoylureas in the Cambridge Crystallographic Database.
  • 62
    • 69549150787 scopus 로고    scopus 로고
    • note
    • 2 torsion angle of around 75° predominating.
  • 64
    • 69549130049 scopus 로고    scopus 로고
    • note
    • It cannot be ruled out that the closed conformation in 8 is not relatively stabilized but that the twisted conformation is relatively destabilized. However, scrutiny of the twisted form of these compounds reveals no reason why 2,6-dimethyl substitution should have such an effect.
  • 65
    • 0002023030 scopus 로고
    • Separation of the NH signals for the two conformations was an unanticipated but useful consequence of the 2,6-dimethyl substitution slowing down the dynamics of conformational interchange. We attribute this to steric hindrance, though a similar phenomenon in certain 2,6-disubstituted tertiary benzamides has been related to an electronic effect on amide resonance. See
    • Separation of the NH signals for the two conformations was an unanticipated but useful consequence of the 2,6-dimethyl substitution slowing down the dynamics of conformational interchange. We attribute this to steric hindrance, though a similar phenomenon in certain 2,6-disubstituted tertiary benzamides has been related to an electronic effect on amide resonance. See: Lewin, A. H.; Frucht, M. Tetrahedron Lett. 1970, 11, 1079-1082.
    • (1970) Tetrahedron Lett. , vol.11 , pp. 1079-1082
    • Lewin, A.H.1    Frucht, M.2
  • 70
    • 0002037724 scopus 로고
    • While π-π stacking appears as though it could contribute to the stability of the twisted conformation of benzanilides (aryl-aryl stacking) and benzoylureas (aryl-amide stacking) as they are depicted in Figure 8, this is either not the case or is insignificant, since N-methylalkylanilides also adopt the twisted conformation (see ref 63). Interestingly, this type of conformational interchange where a twisted form alleviates steric hindrance appears to be a general phenomenon as analogous behavior is observed in N-alkyl-N′-phenylureas see: and has been used as a deliberate design strategy to occupy large pockets in protein-protein interactions
    • While π-π stacking appears as though it could contribute to the stability of the twisted conformation of benzanilides (aryl-aryl stacking) and benzoylureas (aryl-amide stacking) as they are depicted in Figure 8, this is either not the case or is insignificant, since N-methylalkylanilides also adopt the twisted conformation (see ref 63). Interestingly, this type of conformational interchange where a twisted form alleviates steric hindrance appears to be a general phenomenon as analogous behavior is observed in N-alkyl-N′-phenylureas (see: Nowick, J. S.; Abdi, M.; Bellamo, K. A.; Love, J. A.; Martinez, E. J.; Noronha, G.; Smith, E. M.; Ziller, J. W. J. Am. Chem. Soc. 1995, 117, 89-99) and has been used as a deliberate design strategy to occupy large pockets in protein-protein interactions.
    • (1995) J. Am. Chem. Soc. , vol.117 , pp. 89-99
    • Nowick, J.S.1    Abdi, M.2    Bellamo, K.A.3    Love, J.A.4    Martinez, E.J.5    Noronha, G.6    Smith, E.M.7    Ziller, J.W.8
  • 72
    • 0001205946 scopus 로고
    • The geometry of the intramolecular hydrogen bond in the closed conformation of the benzoylurea core is not optimal NH⋯O nonlinear, see: and comprises a donor and acceptor of different pKa's (carbonyl C=O and amide NH). It is clear from these two factors that we are not in presence of the strongest type of hydrogen bond, which is linear and comprises a donor and acceptor of equivalent pKa's (e.g., FHF). The terms "strong" or "weak" are employed as relative characterizations and not in their absolute meaning
    • The geometry of the intramolecular hydrogen bond in the closed conformation of the benzoylurea core is not optimal (NH⋯O nonlinear, see: Peters, D.; Peters, J. J. Mol. Struct. 1980, 68, 255-270) and comprises a donor and acceptor of different pKa's (carbonyl C=O and amide NH). It is clear from these two factors that we are not in presence of the strongest type of hydrogen bond, which is linear and comprises a donor and acceptor of equivalent pKa's (e.g., FHF). The terms "strong" or "weak" are employed as relative characterizations and not in their absolute meaning.
    • (1980) J. Mol. Struct. , vol.68 , pp. 255-270
    • Peters, D.1    Peters, J.2
  • 73
    • 0030090490 scopus 로고    scopus 로고
    • Note that it has been stated that firm conclusions on hydrogen bond strength cannot be drawn from spectral and crystallographic data. See
    • Note that it has been stated that firm conclusions on hydrogen bond strength cannot be drawn from spectral and crystallographic data. See: Guthrie, J. P. Chem. Biol. 1996, 3, 163-170.
    • (1996) Chem. Biol. , vol.3 , pp. 163-170
    • Guthrie, J.P.1
  • 75
    • 69549148168 scopus 로고    scopus 로고
    • note
    • See the Supporting Information.
  • 77
    • 69549098768 scopus 로고
    • The extent of torsional distortion alone, in the absence of bond length data, has been shown to be an unreliable gauge of the extent of conjugation see, for example
    • The extent of torsional distortion alone, in the absence of bond length data, has been shown to be an unreliable gauge of the extent of conjugation (see, for example: Chattopadhyay, D.; Mazumdar, S. K. Z. Kristallogr. 1986, 177, 103-106).
    • (1986) Z. Kristallogr. , vol.177 , pp. 103-106
    • Chattopadhyay, D.1    Mazumdar, S.K.2
  • 78
    • 69549144531 scopus 로고    scopus 로고
    • note
    • 2 bond lengths of 1.41 Å, only marginally shorter than those of a single bond. We are not aware of this phenomenon having previously been reported.
  • 79
    • 69549151610 scopus 로고    scopus 로고
    • note
    • 2 distances are remarkably longer and shorter, respectively, for benzoylureas in the current study than in a comparable amide bond. A full investigation into why this is so is beyond the scope of this paper.
  • 81
    • 69549151611 scopus 로고    scopus 로고
    • note
    • Interestingly, benzoylureas do not appear in Gilli's survey of crystallographic data, although papers by Smith (see ref 23) and Kohmoto (see ref 16) containing the X-ray structure of compound 10 were published before Gilli's study.
  • 85
    • 69549098769 scopus 로고    scopus 로고
    • note
    • The influence of increased rigidity on theNHchemical shift is why 1, for example, is a better model than constrained compounds 12 or 11b for the closed conformation of 3 in our analysis of conformational equilibria in 3 using the NH chemical shift value.
  • 86
    • 69549156137 scopus 로고    scopus 로고
    • note
    • L and have disclosed this to researchers in a variety of formats (see ref 13).


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