A formulation containing an extract of a tobacco plant enriched for a compound of formula (I), or a salt or crystal thereof, where the formulation is used for reducing the infestation of ectoparasites:
where
R represents hydrogen or C
1
-C
5
alkyl, and
represents a double bond.
Optically active nicotine analogs. Synthesis of (S)-(-)-2,5-dihydro-1-methyl-2-(3-pyridyl)pyrrole ((S)-(-)-3',4'-dehydronicotine)