ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
By conventional peptide-coupling methods (C to N direction; mixed anhydride, bis(2)-oxooxazolidin-3-yl)phosphinoyl chloride (Bop-Cl), or dicyclohexylcarbodiimide (DCC), 2-amino-2-methyl-3-(methylamino)-propionic acid and 2-amino-2-ethyl-3-(methylamino)propionic acid ( = 2-amino-2-[(methylamino)methyl]butanoic acid) are incorporated in the central position of tri-, penta-, and heptapeptides (see 3-7, 21, and 22). The fragment coupling of the β -amino group of the diamino-acid moiety in a tetrapeptide led to partial epimerization, and thus, two epimeric heptapeptide derivatives were actually obtained (7 and epi-7). The final deprotection to the free heptapeptide (involving a Me3SiI cleavage of BocNH and MeOCONH, a saponification with NaOH, and HPLC purification) gave both the desired product (isopeptide 21), with the β -amino group inside the peptide backbone, and a product (peptide 22) of transpeptidation, with the α-amino group of the diamino acid incorporated and a (methylamino)methyl group as the side chain. Peptide 22 is completely converted to the isopeptide 21 by prolonged treatment with base. The heptapeptide 21 was analyzed by elaborate 2QF-COSY and NOESY NMR measurements in H2O/CD3OD at -5° (Table, Fig.); there is no indication for β -sheet or helical structures, a fact which was also confirmed by CD measurements.
Additional Material:
1 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19940770728
