Synthesis and biological evaluation of A-ring analogs of the natural germination stimulant strigol

✍ Scribed by E. M. Mangnus; B. Zwanenburg

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 538 KB
• Volume: 111
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19921110308

✦ Synopsis

Abstract

An A‐ring‐derived analog of the natural germination stimulant, Strigol (1), has been prepared from citral in an unambiguous manner. This analog, 2, a γ‐hydroxy aldehyde for which a high stimulant activity was claimed in the literature, has been re‐evaluated as a germination stimulant for seeds of parasitic weeds and was found to be inactive. It was also shown that analog 2 is rather stable in aqueous solution, in contrast to other reports.

In addition, some related A‐ and AB‐ring‐derived analogs have been prepared and biologically evaluated. The γ‐hydroxy acid 12 was obtained in one step from a mixture of α‐ and β‐cyclocitral in 58% yield. The dihydroxy analog 14 was prepared by reduction of the γ‐hydroxy ester 13. The AB‐ring analog 15 has been synthesized in five steps from ester 13 following published procedures. All analogs have been evaluated using Striga and Orobanche seeds; none of the compounds induced germination. It was concluded that the actiphore of strigol does not reside in the AB part of the molecule.