Asymmetric Synthesis of Contact Sex Pheromone of Tetropium fuscum and Its Enantiomer

Abstract

Tetropium fuscum is a harmful forest pest and attacks spruces. The contact sex pheromone of this pest, (S)-11-methyl-heptacosane, and its enantiomer were synthesized via Evans’ chiral auxiliaries. The key steps of this approach included acylation of carboxylic acid, diastereoselective methylation of oxazolidinone amide, and Wittig coupling of the aldehyde with chiral phosphonium salt. The synthetic pheromones would have potential utility in the control of this pest.

Asymmetric Synthesis of Contact Pheromone Component of Xylotrechus colonus and Its Analogues

“…[17,18] In the presence of n-butyllithium, Wittig coupling of 9-(benzyloxy)nonanal (15) with phosphonium salt 10 led to the desired olefinic ether 16 (96 % yield, Z : E = 98 : 2, determined by 13 C NMR spectra). [19,20] The intense resonances for its 13 C NMR spectra were observed at δ 27.35 and 26.34 ppm, which were consistent with the expected chemical shifts for the allylic carbons of a Z-double bond. [21] Therefore, double bond of 16 was assigned as Z.…”

“…The protection of 1,9‐nonanediol ( 13 ) with benzyl chloride produced 9‐(benzyloxy)nonan‐1‐ol ( 14 ), [16] followed by the oxidation with Dess‐Martin periodinane to afford benzyloxy aldehyde 15 [17,18] . In the presence of n ‐butyllithium, Wittig coupling of 9‐(benzyloxy)nonanal ( 15 ) with phosphonium salt 10 led to the desired olefinic ether 16 (96 % yield, Z : E =98 : 2, determined by 13 C NMR spectra) [19,20] . The intense resonances for its 13 C NMR spectra were observed at δ 27.35 and 26.34 ppm, which were consistent with the expected chemical shifts for the allylic carbons of a Z ‐double bond [21] .…”

Enantioselective Synthesis of the Active Sex Pheromone Components of the Female Lichen Moth, Lyclene dharma dharma, and Their Enantiomers

“…As illustrated in Scheme 2 , our synthetic sequence was initiated with the reaction of undec-10-enoic acid ( 3 ) with pivaloyl chloride, which was then converted to oxazolidinone amide ( R )- 5 in 92% yield through acylation of ( R )-4-isopropyloxazolidin-2-one (( R )- 4 ) [ 9 , 10 ]. Enantioselective methylation was then carried out, using methyl iodide (MeI) in the presence of sodium bis(trimethylsilyl)amide (NaHMDS), resulting in ( R )-4-isopropyl-3-(( R )-2-methylundec-10-enoyl) oxazolidin-2-one (( R , R )- 6 ) [ 11 , 12 ]. This step achieved an 82% yield.…”

“…As illustrated in Scheme 5 , we synthesized ( S )-4-isopropyl-3-tetradecanoyloxazolidin-2-one (( S )- 14 ) by reacting tetradecanoic acid ( 13 ) with the ( S )-Evans’ chiral auxiliary (( S )- 4 ) in 81% yield [ 9 , 10 ]. Subsequent asymmetric methylation using sodium bis(trimethylsilyl)amide (NaHMDS) and methyl iodide (MeI) produced ( S )-4-isopropyl-3-(( S )-2-methyltetradecanoyl) oxazolidin-2-one (( S )- 15 ) in 75% yield [ 12 ]. Reduction of compound ( S )- 15 with lithium aluminum hydride (LiAH 4 ) yielded ( S )-2-methyltetradecan-1-ol (( S )- 16 ) in 77% yield [ 14 ], with a specific rotation of −10.59 (c 1.13, CHCl 3 ), consistent with the value reported in the literature of −11.36 (c 0.88, CHCl 3 ) [ 23 ].…”