109927-44-8Relevant articles and documents
Inverse γ-Turn-Inspired Peptide: Synthesis and Analysis of Segetalin A Indole Hemiaminal
Lamping, Matthias,Enck, Sebastian,Geyer, Armin
, p. 7443 - 7448 (2015)
Substitution of a peptide bond for an imine transforms the irreversible macrocyclization of peptides into a reversible process. The inherent cyclization tendency of a linear peptide is then analyzable through the equilibrium between the aldehyde and the imine by virtue of the higher reactivity of the corresponding linear peptide aldehyde. The tryptophan side chain of segetalin A aldehyde forms a 12-membered cyclic indole hemiaminal instead of the 18-membered macrocyclic imine expected. Herein, we analyzed this uncommon hemiaminal that shows that the biosynthesis of cyclic peptides is not necessarily based on linear precursor peptides with a high inherent macrolactamization tendency. By substituting a peptide bond for an imine, the cyclization tendency of a linear peptide can be analyzed through equilibration of the aldehyde and imine forms. The tryptophan side chain of segetalin A aldehyde forms a 12-membered cyclic indole hemiaminal instead of the expected 18-membered macrocyclic imine. Herein, we analyze this uncommon hemiaminal.
Dendritic biomimicry: Microenvironmental hydrogen-bonding effects on tryptophan fluorescence
Koenig, Stephanie,Mueller, Lars,Smith, David K.
, p. 979 - 986 (2001)
Two series of dendritically modified tryptophan derivatives have been synthesised and their emission spectra measured in a range of different solvents. This paper presents the syntheses of these novel dendritic structures and discusses their emission spectra in terms of both solvent and dendritic effects. In the first series of dendrimers, the NH group of the indole ring is available for hydrogen bonding, whilst in the second series, the indole NH group has been converted to NMe. Direct comparison of the emission wavelengths of analogous NH and NMe derivatives indicates the importance of the Kamlet-Taft solvent β parameter, which reflects the ability of the solvent to accept a hydrogen bond from the NH group, an effect not possible for the NMe series of dendrimers. For the NH dendrimers, the attachment of a dendritic shell to the tryptophan subunit leads to a red shift in emission wavelength. This dendritic effect only operates in non-hydrogen bonding solvents. For the NMe dendrimers, however, the attachment of a dendritic shell has no effect on the emission spectra of the indole ring. This proves the importance of hydrogen bonding between the branched shell and the indole NH group in causing the dendritic effect. This is the first time a dendritic effect has been unambiguously assigned to individual hydrogen-bonding interactions and indicates that such intramolecular interactions are important in dendrimers, just as they are in proteins. Furthermore, this paper sheds light on the use of tryptophan residues as a probe of the microenvironment within proteins - in particular, it stresses the importance of hydrogen bonds formed by the indole NH group.
Substrate Fragmentation for the Design of M. tuberculosis CYP121 Inhibitors
Kavanagh, Madeline E.,Gray, Janine L.,Gilbert, Sophie H.,Coyne, Anthony G.,McLean, Kirsty J.,Davis, Holly J.,Munro, Andrew W.,Abell, Chris
supporting information, p. 1924 - 1935 (2016/10/06)
The cyclo-dipeptide substrates of the essential M. tuberculosis (Mtb) enzyme CYP121 were deconstructed into their component fragments and screened against the enzyme. A number of hits were identified, one of which exhibited an unexpected inhibitor-like binding mode. The inhibitory pharmacophore was elucidated, and fragment binding affinity was rapidly improved by synthetic elaboration guided by the structures of CYP121 substrates. The resulting inhibitors have low micromolar affinity, good predicted physicochemical properties and selectivity for CYP121 over other Mtb P450s. Spectroscopic characterisation of the inhibitors′ binding mode provides insight into the effect of weak nitrogen-donor ligands on the P450 heme, an improved understanding of factors governing CYP121–ligand recognition and speculation into the biological role of the enzyme for Mtb.
