Stereospecific inversion of secondary tosylates to yield chiral methyl-branched building blocks, applied to the asymmetric synthesis of leafminer sex pheromones

All four of the possible stereoisomers of 5,9-dimethylheptadecane, the major sex pheromone component secreted by female moths of the mountain-ash bentwing (Leucoptera scitella), were synthesized by the coupling of two chiral blocks with a methyl branch at the 2- or 3-position. The blocks were prepared by applying the stereospecific inversion of secondary tosylates, which were derived from (R)- and (S)-propylene oxide, and their enantiopurities were confirmed by chiral HPLC analysis.

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(5S,9R)-5,9-DimethylheptadecaneC19H40[α]D23=+1.1 (c 0.63, CHCl3)Absolute configuration: (5S,9R)

(5S,9S)-5,9-DimethylheptadecaneC19H40[α]D23=+2.2 (c 1.3, CHCl3)Absolute configuration: (5S,9S)

(R)-2-HexanolC6H14O[α]D23=-8.1 (c 1.5, CHCl3)Absolute configuration: (R)

(R)-2-Hexanyl tosylateC13H20O3S[α]D23=-3.7 (c 2.0, CHCl3)Absolute configuration: (R)

(S)-Methyl 3-methylheptanoateC9H18O2[α]D23=-3.1 (c 0.82, CHCl3)Absolute configuration: (S)

(S)-3-Methylheptan-1-olC8H18O[α]D23=+2.7 (c 1.2, CHCl3)Absolute configuration: (S)

(S)-1-Iodo-3-methylheptaneC8H17I[α]D23=-12.6 (c 1.4, CHCl3)Absolute configuration: (S)

(S)-2-DecanolC10H22O[α]D23=+8.1 (c 1.1, CHCl3)Absolute configuration: (S)

(S)-2-Decanyl tosylateC17H28O3S[α]D23=-3.5 (c 2.0, CHCl3)Absolute configuration: (S)

2-Methyl-1-(4-methylphenylsulfonyl)decaneC18H30O2S[α]D23=-1.1 (c 2.5, CHCl3)Absolute configuration: (R)