Inhibitors of a 9-cis epoxycarotenoid dioxygenase

(4S,5R)-(3′Z)-4-(5′-(Ethylthio)-3′-methylpent-3′-en-1′-ynyl)-4-hydroxy-3,3,5-trimethylcyclohexanone, (4R,5S)-(3′Z)-4-(5′-(ethylthio)-3′-methylpent-3′-en-1′-ynyl)-4-hydroxy-3,3,5-trimethylcyclohexanone,

• (4S,5R/4R,5S)-(3′Z)-4-(5′-(ethylthio)-3′-methylpent-3′-en-1′-ynyl)-4-hydroxy-3,3,5-trimethylcyclohexanone,
• (1S,4R,6R)-(3′Z)-1-(5′-(ethylthio)-3′-methylpent-3′-en-1′-ynyl)-2,2,6-trimethylcyclohexane-1,4-diol,
• (1R,4R,6R)-(3′Z)-1-(5′-(ethylthio)-3′-methylpent-3′-en-1′-ynyl)-2,2,6-trimethylcyclohexane-1,4-diol,
• (2Z,4E)-5-(1-hydroxy-2′,2′,6′-trimethyl-4′-oxocyclohexyl)-3-methylpenta-2,4-dienyl 2-(thiophen-2″-yl) acetate,
• (1R,3S,6R)-(3′Z)-1,5,5-trimethyl-6-(3′-methyl-5′-(phenylthio)-pent-3′-en-1′-ynyl)-7-oxa-bicyclo[4.1.0]heptan-3-ol,
• (1R,3S,6R)-(3′Z)-1,5,5-trimethyl-6-(3′-methyl-5′-(phenylamino)-pent-3′-en-1′-ynyl)-7-oxabicyclo[4.1.0]heptan-3-ol,
• or a plant physiologically acceptable salt thereof.

A method of inhibiting 9-cis-epoxycarotenoid dioxygenase (NCED) in a plant or seed comprising administering to the plant or seed a 9-cis-epoxycarotenoid dioxygenase inhibiting effective amount of a compound of formula (I):

• wherein:
• R1 is —SR10, —O—C(O)—R11, —NR12R13, where R10 is a C1-8-alkyl group or a phenyl group unsubstituted or substituted by a C1-4-alkyl group, R11 is a thiophenenyl, furanyl or pyrrolyl group, R12 is H or a C1-4-alkyl group and R13 is a C1-8-alkyl group or a phenyl group unsubstituted or substituted by a C1-4-alkyl group;
• R2 is H or a C1-4-alkyl group;
• R3 and R4 are independently H or C1-4-alkyl groups;
• R5 and R6 are independently H, OH or OR14, or taken together are ═O, where R14 is a protecting group;
• R7 is H or a C1-4-alkyl group;
• and, R8 is H, R9 is OH and R15 is H, or R15 is H and R8 and R9 taken together are —O—, or R9 is OH and R8 and R15 taken together form a bond;
• and,
• R18 and R19 are both H, or R18 and R19 taken together form a bond,
• or a plant physiologically acceptable salt thereof.