Peptides in higher plants. II. The crystal structure of tri N methylfrangulanine methiodide

• Published in: Chemical & pharmaceutical bulletin Vol. 24; no. 9; pp. 2181 - 2184
• Main Authors: Takai, M, Ogihara, Y, Iitaka, Y, Shibata, S
• Format: Journal Article
• Language: English
• Published: Tokyo The Pharmaceutical Society of Japan 1976; Japan Science and Technology Agency
• Subjects: plant biochemistry; plant physiology
• ISSN: 0009-2363; 1347-5223
• DOI: 10.1248/cpb.24.2181

The crystal structure of tri-N-methylfrangulanine methiodide, C32H54O4N4I has been determined in order to clarify the conformation and absolute configuration of frangulanine, C28H44O4N4, a peptide alkaloid isolated from Hovenia dulcis. The crystals are orthorhombic with space group P212121 and unit cell dimensions are a=8.826 (8), b=49.95 (2), c=8.296 (8) A, Z=4. The crystal structure was solved by the heavy-atom method and refined by the block-diagonal least-squares method including anisotropic thermal parameters. The final R value for 1383 observed structure factors was 0.10. The absolute configuration was determined by the use of the anomalous dispersion of iodine atom for Cu Kα radiation. Frangulanine is composed of all L-amino acids and the conformation of the peptide units is of the β-pleated sheets structure.