Improved synthesis of strigol analogue GR24 and evaluation of the biological activity of its diastereomers
1992
Dommerholt, F.J. | Jong, R.L.P. de | Zwanenburg, B.
A high yield preparation procedure for the germination stimulant GR24 (2) is described. Improvements were introduced in the syntheses of the key building blocks 3 and 4. The tricyclic lactone 3 was prepared from indan-1-one in four steps. The major improvement was the introduction of the carboxymethyl function at the alpha-position of indan-1-one via an ethoxycarbonyl auxiliary group. The furanone moiety 4 was prepared in four steps in an overall yield of 75% using ethyl alpha-bromopropionate and oxirane as main starting materials. The final coupling afforded GR24 as a mixture of diastereomers, which were separated by chromatography. The separate diastereomeric racemates 2a and 2b were fully characterized, and the configuration was determined by X-ray analysis. Biological tests of the diastereomers demonstrated differences in their stimulatory activities for parasitic weed seeds.
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