Peptidkonformationen, 22. Die Konformation von cyclo‐[Pro₂‐(NB)Gly] im Kristall und in Lösung durch Röntgenstrukturanalyse und ein‐ und zweidimensionale NMR‐Spektroskopie

Abstract

Die Konformation des cyclischen Tripeptides cyclo-[Pro2-(NB)Gly] (NBThe conformation of the cyclic tripeptide cyclo-[Pro2-(NB)Gly] (NB = o-Nitrobenzyl) was investigated by X-ray analysis and NMR spectroscopy. The backbone conformation is -according to X-ray analysis -a boat for crystals grown from methanol or chloroform. The crystal structure was correlated with the conformation in solution by solid state 13C-CP-MAS-NMR spectroscopy as well as by dissolving of different crystals at low temperatures followed by NMR spectroscopy of the solutions. In solution a solvent dependent equilibrium -slow on the NMR time scale -between a boat and a crown conformation is observed. The assignment of the I3C NMR spectrum was performed Ilia a 2D-'H-I3C shift correlation. The synthesis of the compound is described.Die zur Zeit bewahrtesten Methoden der Strukturuntersuchung sind die Rontgenstrukturanalyse und die NMR-Spektroskopie. Die komplementaren Einsatzgebiete (Kristall und Losung) beider Verfahren kannen durch die Festkorper-NMR-Spektros-0 Verlag

Controversy of Peptide Cyclization from Tripeptide

“…In contrast, in the case of reported natural product 1 , ring carbonyl peak values for proline and glycine are much higher (δ 174.8 and 169.8 ppm) than for other reported cyclic tripeptides [ 34 , 35 , 36 ] and closer to our synthetic cyclic hexapeptide cyclo (GPE) 2 2 (δ 173.8 and 169.6 ppm). Table 2 shows complete comparison of 13 C chemical shift values of cyclo (GPE) 1 [ 8 ] and cyclo (GPE) 2 2 .…”

“…All the ring carbonyl peak values of reported cyclic tripeptides are lower than 170 ppm [ 34 , 35 , 36 ]. Carbonyl peak of proline in cyclo ( l -Pro- l -BnG- d -Pro) [ 34 ], cyclo (Pro-Pro-BnG) [ 35 ], cyclo ( l -Pro- l -Pro- d -Pro) [ 35 ] and cyclo ( l -Pro- l -Pro- l -Pro) [ 36 ] showed peaks between δ 167 and 169 ppm. Glycine carbonyl [ 36 ], just like proline, also appeared in the range around δ 166 ppm.…”

Synthesis and Photochemistry of Photolabile Derivatives of .gamma.-Aminobutyric Acid for Chemical Kinetic Investigations of the .gamma.-Aminobutyric Acid Receptor in the Millisecond Time Region

“…Reductive amination of 2-nitrobenzaldehyde with GABA in the presence of sodium borohydride yields TV-(2-nitrobenzyl)--aminobutyric acid in 65% yield. This procedure is an extension of the method reported by Kessler et al (1983) for the synthesis of TV-(2-nitrobenzyl)glycine. ieri-Butyl 4-bromobutyrate was prepared from 4-bromobutyric acid, isobutylene, and catalytic amounts of sulfuric acid in the presence of 4-A molecular sieves with dioxan as the solvent, in a pressure bottle (Anderson & Callahan, 1960).…”

Synthesis and photochemistry of photolabile N-glycine derivatives and effects of one on the glycine receptor

“…N-(2-Nitrobenzyl)glycine (I). Method A. Compound I was prepared as reported by Kessler et al (1983) from 2-nitrobenzaldehyde (0.15 g, 1 mmol), glycine (0.113 g, 1.507 mmol), sodium hydroxide (0.06 g, 1.5 mmol, 0.75 mL of 2 N), methanol (1.5 mL), and sodium borohydride (0.03 g, 0.79 mmol) and purified by vacuum liquid chromatography (Coll et al, 1977) on silica gel absorbent (10-40 #tm, type H, Sigma), using 0.1% acetic acid in ethanol as the eluent whose polarity was gradually increased by addition of water: mp [189][190][191] °C; yield, 15%. NMR (D20-K2C03): 8.13 (m, 1 H, C3-H), 7.72 (m, 1 H, C6-H), 7.59 (m, 2 H, C4 and C5-H), 4.42 (s, 2 H, benzylic), and 3.61 (s, 2 H, methylene).…”