Antitumor agents XVII: Structure and stereochemistry of microhelenin-a, a new antitumor sesquiterpene lactone from Helenium microcephalum

✍ Scribed by Kuo-Hsiung Lee; Yasuhiro Imakura; Donald Sims

• Publisher: John Wiley and Sons
• Year: 1976
• Tongue: English
• Weight: 651 KB
• Volume: 65
• Category: Article
• ISSN: 0022-3549
• DOI: 10.1002/jps.2600650940

✦ Synopsis

Keyphrases 0 Antitumor agents, potential-microhelenin-A, isolated from Helenium microcephalum, NMR spectral identification 0 Microhelenin-A-potential antitumor agent, isolated from Helenium microcephalurn, NMR spectral identification 0 Helenium microcephalum-microhelenin-A, potential antitumor agent, isolated and identified

To the Editor:

The search for a supply of helenalin for investigations on the relationship between the sesquiterpene lactone structure and cytotoxic antitumor activity (1) led to the isolation of a new antitumor' (2) sesquiterpene lactone, microhelenin-A (Structure I), from Helenium micro-cephalum2 (3).

Microhelenin-A was isolated as colorless needles in 0.005% yield from the chloroform extract of H. microcephalum according to an exact literature procedure (4) followed by silica gel column chromatography. Microhelenin-A [mp 140-141°, [a18 +89O (c, 1 in methanol3, mle 262 (M+)] has the molecular formula4 C15H1804 and showed the presence of a cyclopentanone ring system (1758 cm-I). The presence of an a-methylene-ylactone moiety in Structure I was indicated by the appearance of IR bands (CC14) at 1772 and 1665 cm-' and was substantiated by the presence in the NMR spec-trum5 of a characteristic pair of low field doublets at 6