A 13C and 15N experimental NMR and theoretical study of the structure of linear primary aliphatic amines and ammonium salts: from C1 to C18

Sanz, Dionísia; Claramunt, Rosa M.; García, M. Ángeles; Alkorta, Ibón; Elguero, José

doi:10.1016/j.tet.2011.04.067

Cited by 15 publications

(17 citation statements)

References 35 publications

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“…Synthesis of new rifampicin amino analogues [3][4][5][6][7][8][9][10][11][12][13] Rifampicin was hydrolyzed into rifaldehyde and next converted into its new benzyl and phenethyl amino analogues (Fig. 2) via four reductive amination methods (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, chemical shifts of N(38) signals in 15 N NMR spectra of 3-13 are in a narrow range from −329 to −334 ppm (see the Experimental section), typical of protonated amines. 13 The 1 H NMR chemical shifts of the two geminal (38)N + -H protons are different (Fig. 7) because of the fact that these protons are diastereotopic due to the chirality of the molecule combined with the prochiral quaternary nitrogen center 14 and different character of hydrogen bonds in which these protons are involved.…”

Section: Structure Of New Rifampicin Amino Analogues 3-13 In Solutionmentioning

confidence: 99%

“…It should be noted that for 3-13 analogues there are several possible combinations of different C( 16)vC (17) and C(18)v C( 19) double bond configurations with different conformations of the diene moiety (s-cis and s-trans). Assignment of H( 18) and H (19) proton signals with the use of 1 H- 13 C HSQC and 1 H- 13 C HMBC methods and determination of three-bond coupling constants 3 J H18-H19 ≈ 15.5 Hz and 3 J H19-H20 ≈ 7. 5 Hz for 3-13 compounds evidenced the E-configuration of the C( 18)vC( 19) bond.…”

Section: Structure Of New Rifampicin Amino Analogues 3-13 In Solutionmentioning

confidence: 99%

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A new model of binding of rifampicin and its amino analogues as zwitterions to bacterial RNA polymerase

et al. 2012

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Seven new benzyl (3-9) and four new phenethyl (10-13) amino analogues of ansa-macrolide rifampicin (1) were synthesized using the optimised method of reductive amination. Structures of 3-13 in solution were determined by 1D and 2D NMR and FT-IR methods whereas the energetically most favoured conformation of amino analogues was calculated with the use of the PM5 method. Spectroscopic and semi-empirical studies revealed the presence of zwitterionic forms of all 3-13 analogues in solutions containing water traces. (1)H-(15)N HSQC and (1)H-(15)N HMBC in combination with (1)H-(1)H COSY and (1)H-(13)C HMBC two dimensional spectroscopic methods unambiguously evidenced that the presence of the zwitterionic form of ansa-macrolides was a consequence of proton transfer from the O(8)-H phenolic group to the secondary amine moiety within 3-13 structures. (1)H-(1)H NOESY studies indicated two different orientations of the substituent introduced at the C(3) position for benzyl and phenethyl amino analogues of rifampicin and their similar conformation within the ansa-bridges in solution. FT-IR studies of the deprotonation of molecule and comparison of these data with those for indicated 3-13 C(8)=O double bond character after formation of zwitterions in solution. Results of an antibacterial test against Gram-(-) and Gram-(+) strains were compared with detailed structural information on new analogues of 3-13 to indicate some structure-activity relationships. Molecular recognition studies of 1 and 12 inhibitors at the binding site of bacterial RNA polymerase (RNAP) as zwitterions revealed key intermolecular interactions and led to the proposition of a new model of RNAP inhibition, which explains significant differences in antibacterial properties of rifampicin and its analogues.

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Section: Resultsmentioning

confidence: 99%

Section: Structure Of New Rifampicin Amino Analogues 3-13 In Solutionmentioning

confidence: 99%

Section: Structure Of New Rifampicin Amino Analogues 3-13 In Solutionmentioning

confidence: 99%

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A new model of binding of rifampicin and its amino analogues as zwitterions to bacterial RNA polymerase

et al. 2012

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“…Tautomeric populations of each charge state were then obtained by constrained least‐squares fitting of the theoretically calculated 15 N NMR chemical shifts of the tautomers to the observed shifts. Correlation analyses of calculated chemical shieldings and experimental chemical shifts have been earlier used to analyze conformational and tautomeric mixtures . However, studies applying optimization techniques in determining populations are rare .…”

Section: Introductionmentioning

confidence: 99%

Tautomeric populations of the charged species of 1,12-diamino-3,6,9-triazadodecane (SpmTrien) studied with computer simulations and cluster expansions

Weisell

Vepsäläinen

Peräkylä

2013

J. Phys. Org. Chem.

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Correct net charge and protonation pattern in the polyamine backbone is one of the major factors that define the interactions of this class of compounds. 1,12‐diamino‐3,6,9‐triazadodecane (SpmTrien) is a isosteric charge deficient analogue of naturally occurring spermine (Spm) with different biological features. The tautomeric populations of each SpmTrien charge state were estimated with computer simulations, molecular dynamics (MD) and quantum mechanical calculations, and cluster expansions separately. In the computer simulations, tautomeric populations of each charge state were obtained by constrained least‐squares fitting the theoretically calculated (GIAO B3LYP/6‐311 + G**) 15 N NMR chemical shieldings of SpmTrien tautomers to the experimentally measured chemical shifts. Theoretical chemical shieldings were calculated for water complexes of SpmTrien obtained from MD simulations in explicit water. Both methods gave highly similar realistic results. SpmTrien has many major populations of tautomers at biologically relevant charge states of three (+3) and four (+4) thus enabling a large variety of structures for specific ionic interactions. Copyright © 2013 John Wiley & Sons, Ltd.

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“…Taking into account that data measured in the solid state deviate from those in solution, 44,45 and that 13 C C-Br signals need to be corrected, 46,47 the results of …”

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confidence: 99%

A theoretical study of the mechanism of oxidation of 1H-pyrazolines to 1H-pyrazoles by molecular bromine

Alkorta¹,

Elguero²

2013

Arkivoc

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A 13C and 15N experimental NMR and theoretical study of the structure of linear primary aliphatic amines and ammonium salts: from C1 to C18

Cited by 15 publications

References 35 publications

A new model of binding of rifampicin and its amino analogues as zwitterions to bacterial RNA polymerase

A new model of binding of rifampicin and its amino analogues as zwitterions to bacterial RNA polymerase

Tautomeric populations of the charged species of 1,12-diamino-3,6,9-triazadodecane (SpmTrien) studied with computer simulations and cluster expansions

A theoretical study of the mechanism of oxidation of 1H-pyrazolines to 1H-pyrazoles by molecular bromine

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