Pheromone synthesis. Part 247: New synthesis of the enantiomers of 13-methylheptacosane, the female sex pheromone of pear psylla, Cacopsylla pyricola

Both the crystalline enantiomers of 13-methylheptacosane, the female sex pheromone of Cacopsylla pyricola, were synthesized in gram quantities by starting from the enantiomers of citronellal, 1-bromodecane and 1-bromoundecane in 23–28% overall yield (eight steps).

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(S)-2,6-Dimethyl-2-octadeceneC20H40[α]D22=-2.33 (c 4.81, hexane)Source of chirality: (R)-citronellalAbsolute configuration: (S)

(S)-4-MethylhexadecanalC17H34O[α]D21=-1.05 (c 5.05, hexane)Source of chirality: (R)-citronellalAbsolute configuration: (S)

(R)-13-MethylheptacosaneC28H58[α]D22.5=-0.045 (c 5.22, CHCl3)Source of chirality: (S)-citronellalAbsolute configuration: (R)