Description
Cinmethylinwas developed by Shell Chemical
Company in the early 1980s as a weed control agent for
monocotyledonous species. This herbicide controls important
grasses such as green foxtail (Setaria viridis) and
barnyardgrass (Echinochloa crus-galli) and suppresses
the growth of several broadleaf weeds such as prickly
sida (Sida spinosa) and velvetleaf (Abutilon theophrasti).
Uses
Cinmethylin is used as pre-emergence grass herbicide. Cinmethylin is member of the cineole eucalyptol family.
Definition
ChEBI: Exo-(+)-cinmethylin is a 1-methyl-2-[(2-methylbenzyl)oxy]-4-(propan-2-yl)-7-oxabicyclo[2.2.1]heptane that is the exo-(+)-isomer of cinmethylin. It is an enantiomer of an exo-(-)-cinmethylin.
Production Methods
Cinmethlyn is commercially synthesised through a multi-step process involving the construction of a 7-oxabicyclo[2.2.1]heptane ring system. The production begins with the formation of the bicyclic ether core, followed by selective alkylation and etherification steps to introduce the methyl, isopropyl, and methoxybenzyl substituents. These reactions are carried out under controlled conditions to ensure stereoselectivity and purity, with final purification achieved through distillation or crystallisation.
Mechanism of action
Selective, systemic, absorbed by roots and translocated. Disrupts the meristemic development in shoots and roots of susceptible weeds.
Pharmacology
Cinmethylin is active on several important grasses in
rice (Echinochloa spp., Cyperus spp., and Monochoria
vaginalis) at rates from 25 to 100 g ai/ha (5). Its chemical
and toxicological features (low persistence in environment
and low mammalian toxicity) generated a significant level
of interest in its use as a rice herbicide.
Metabolic pathway
When rats are administered 14C-cinmethylin orally, the
major route of its elimination is via urinary excretion. A
complex degradation pattern of cinmethylin is
observed and the metabolic pathways involve
hydroxylation, oxidation at the benzyl and cineol
portions, conjugation with glucuronic acid and glycine,
and cleavage of the ether linkage. When rats are
administered 14C-cinmethylin by stomach incubation,
two minor metabolites are identified as o-
(acetoxymethyl)benzoic acid and 9-(acetoxymethyl)-a-
carboxycinmethylin.
