Crystal-state structures of Boc-Pro-Leu-Gly-NH2, hemihydrate and two lactam-restricted analogues
- 1 January 1989
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 1,p. 83-87
- https://doi.org/10.1039/p29890000083
Abstract
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-t-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.Keywords
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