SYNTHESIS AND BIOLOGICAL-ACTIVITY OF ALLENIC ANALOGS OF ABSCISIC-ACID

Novel allenic analogues of abscisic acid (ABA) were synthesized and tested for ABA activity. The allene functional group was introduced by one of two methods: base catalysed isomerization of an enyne to an enallene conjugated to a ketone, or reduction of a 2-butyn-1,4-diol to an allenic alcohol. A 3:1 mixture of (E)- and (Z)-3-methyl-5-(4',4'-ethylenedioxy-2',6',6'-trimethylcyclohex-2'-en-1'-ylidene)-2,4,5-pentatrienoic acids strongly prohibited growth of axenic duckweed (Lemna gibba) causing a 50% reduction in frond number at 60-mu-g l-1 over 7 days in continuous light. Racemic ABA caused the same inhibition at 130-mu-g l-1. The mixture caused the production of turion-like structures, an effect known hitherto to be induced only by short photoperiods or by certain concentrations of ABA.