The synthesis of the insect pheromone (2S,3R,7R)-3,7-dimethyltridec-2-yl acetate from racemic 3,4-dimethyl-γ-butyrolactone by diastereoselective chiral resolution

The insect pheromone (2S,3R,7R)-3,7-dimethyltridec-2-yl acetate 1-Ac was prepared from diastereomerically enriched (2S∗,3R∗,7R)-1, which in turn was obtained by the coupling of racemic 3,4-dimethyl-γ-butyrolactone with (7S)-2-methyloctyllithium, followed by a Wolff–Kishner reduction of the resulting ketone. Conversion of (2S∗,3R∗,7R)-1 to the corresponding alkyl hydrogen phthalate and diastereomer salt formation with (S)-PhCHMeNH2 provided after several crystallizations individual diastereomer, which was later transformed into target 1-Ac after hydrolysis and acylation.

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(2R)-1-Chloro-2-methyloctaneC9H19ClEe 95%[α]D20=+3.3 (c 34.8, hexane)Source of chirality: baker’s yeastAbsolute configuration: (2R)

(2S,3R,7R)-3,7-Dimethyltridecan-2-olC15H32OEe >99%; dr >99:1[α]D20=+16.5 (c 4.8, hexane)Source of chirality: diastereomeric salt formationAbsolute configuration: (2S,3R,7R)

(2S,3R,7R)-3,7-Dimethyltridec-2-yl acetateC17H34O2Ee >99%; dr >99:1[α]D20=+8.3 (c 2.7, hexane)Source of chirality: diastereomeric salt formationAbsolute configuration: (2S,3R,7R)