Co‐oligopeptides containing two aromatic residues spaced by glycyl residues. X. Proton magnetic resonance study of co‐oligopeptides of tryptophan and glycine

Abstract

SynopsisThe 'H-nmr spectra of co-oligopeptides of tryptophan and glycine with structure H-GlyTrp-(Gly),-Trp-Gly-OH (n = 0-2) and those of several di-and tripeptides have been recorded a t 360 MHz with CDBOD solutions containing 0.1N NaOD. The assignment of resonance signals was generally possible by comparing the spectra of structurally related peptides with each other. In order to solve the remaining ambiguities in the assignment, H-(cuL,BS)(cu,@-dz)Trp-OH, H-Trp-((~L,BS)(cu,P-ds)Trp-0H, and H -T r p -( 6 1 , r 2 ,~,~~,~2 -d~) T r p -O H have been prepared and their spectra compared with those of the undeuterated compounds. The distribution of rotamers around the X I and (in two cases) x 2 torsion angles of the side chains has been obtained from the vicinal coupling constants ' J J H~J H~ and from the long-range coupling constants 4 J~a~a~. These data and an analysis of the chemical shifts of the Gly-CC( protons suggest that the orientation of the aromatic side chain is influenced by the following order of decreasing interaction with the functional groups a t N-and C-side: -NH2 > -NHCO-> -CONH-> -COO-. This rule does not hold for the second Trp residue of diand tripeptides containing the -Trp -7'rp-sequence, which has tentatively been attributed to steric effects.

Fluorescence Decay Characteristics of Indole Compounds Revealed by Time-Resolved Area-Normalized Emission Spectroscopy

“…This assignment was consistent with the data proposed by Petrich et al 39 although the population ratio of rotamers was slightly incompatible, and the ratio obtained by our data was also inconsistent with the one obtained by NMR. 17 These discrepancies might be due to solvent condition, and the fraction of rotamers proposed here is not one in the ground-state but the fluorescence fraction which depends on optical parameters and quantum yields of each rotamer. In this study, any trace indicating conformational exchange between rotamers was not observed.…”

Solid-Phase Total Synthesis of Dehydrotryptophan-Bearing Cyclic Peptides Tunicyclin B, Sclerotide A, CDA3a, and CDA4a using a Protected β-Hydroxytryptophan Building Block

“…For example, Oba and coworkers were able to obtain a N α -acylated dehydrotryptophan 1.24 in good yield (Scheme 1.10); whereas, in earlier work, yields of 20% and 26% were obtained by Kirby et al and Skrabl et al respectively in the synthesis of a very similar indole-N-protected acyl-dehydrotryptophan 1.26 (Scheme 1.11). [35][36][37] In both scenarios, the Z-dehydrotryptophan was formed exclusively.…”

Molecular mechanics analysis of Tet repressor TRP-43 fluorescence

“…Each conformation has a different microenvironment, yielding to a distinct nonradiative decay rate due to a different proximity and orientation to quencher groups (Szabo and Rayner, 1980;Petrich et al, 1983). The existence of stable Trp rotamers has been observed by NMR (Skrabal et al, 1979;Dezube et al, 1981). The fluorescence decay of individual Trp rotamers in supersonic jets is monoexponential (Phillips et al, 1988).…”