A crystal-state structural analysis of Boc-Pro-Leu-Gly-NH2 (2a) hemihydrate and two conformationally restricted analogues that incorporate a γ- or δ-lactam modification at the -Leu-Gly- sequence, (3) and (4) respectively, has been performed by X-ray diffraction. In all three compounds the conformation of the tertiary amide group of the Nα-protecting urethane moiety is cis and the prolyl residue is semi-extended. The basic conformational feature of the published structure of H-Pro-Leu-Gly-NH2 (1), the ten-membered ring type-II β-bend structure at the C-terminus, is preserved in the Nα-butyloxycarbonyl derivative (2a). However, the γ- and δ-lactam modifications induce drastic changes in the backbone torsion angles of the -Leu-Gly- sequence, eventually promoting the onset of extended conformations.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of the Chemical Society, Perkin Transactions 2|
|State||Published - 1989|