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Title: CHIRAL SYNTHESIS OF (+)-8'-DEMETHYL ABSCISIC ACID

Author
item ROSE, PATRICIA - PBI, NRI, SASK, CANADA
item LEI, BO - PBI, NRI, SASK, CANADA
item SHAW, ANGELA - PBI, NRC, SASK, CANADA
item Simmons, Mary
item NAPPER, SCOTT - UNIV OF SASK, SK, CANADA
item QUAIL, J - UNIV OF SASK, SK, CANADA
item ABRAMS, SUZANNE - PBI, NRC, SASK, CANADA

Submitted to: Canadian Journal of Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Rain falling on mature wheat in the field can cause sprouting damage. Sprouted wheat has lower grain quality and has to be sold at a discount. The plant hormone, ABA (abscisic acid) can prevent embryo sprouting or germination in wheat. We are determining the structural features of the ABA molecule responsible for the effectiveness of ABA as a germination inhibitor. In this report we have determined the effect of altering the ABA molecule at the 8'-methyl group. We report the synthesis of an ABA molecule lacking the 8'methyl group. The effect of removing the 8'methyl group was tested on inhibition of wheat embryo germination and for reducing transpiration in wheat seedlings. Only a small reduction in ABA-like activity was found with this altered ABA molecule in both biological assays. Our results show that the 8'methyl group is not absolutely required for ABA biological activity, and that this part of the molecule can be modified without a major effect on activity. This new information can be used by plant scientists to design more effective forms of ABA for practical agricultural use aimed at reducing sprouting damage and quality loss in cereals.

Technical Abstract: An enantioselective synthesis of (+)-8'-demethyl ABA (2) is described. The chiral intermediate 7 was prepared by yeast reduction of a substituted monoprotected cyclohexa-2,5-dien-1, 4-dione (9) synthesized through a phenol oxidation. The scope and limitations of the phenol oxidation is described. 8'-Demethyl ABA shows ABA-like activity in wheat embryo germination inhibition, showing that the 8'-methyl group is not essential for biological activity.