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

Enantiospecific synthesis and filed evaluation of four stereoisomers of 10,14-dimethyloctadec-1-ene, a sex pheromone component secreted by female moths of the apple leafminer

“…13) Two kinds of chiral building blocks with a methyl branch at the 3-or 2-position could be obtained by selecting an appropriate carbanion as a nucleophile, and a 1,5-dimethyl structure was produced by their coupling. We successfully confirmed perfect configurational inversion by enantioselective HPLC analysis and accomplished enantiospecific synthesis of 5,9-dimethylheptadecane, 13) which was a main pheromone component of another leafminer species Leucoptera scitella. To demonstrate the usefulness of the S N 2 reaction of secondary tosylates and develop the study about methyl-branched pheromones, we aimed to synthesize all four stereoisomers of 1 and evaluate the activity against the Japanese population of the apple leafminer.…”

“…13) In this study, we applied the opposite strategy in order to avoid isomerization of a terminal double bond, which was expected to be caused by a strong basic condition for preparation of a sulfonyl compound. Long-chain iodides (S)-7 and (R)-7 were synthesized from (R)-2 and (S)-2, respectively [ Fig.…”

“…1(B)], in a similar manner as that for the synthesis of two stereoisomers of 1-iodo-3-methylheptane. 13) The reaction between (R)-2 and a Grignard reagent prepared from 8-bromooct-1-ene with a catalytic amount of Li 2 CuCl 4 produced a secondary alcohol (R)-3, which was converted to a tosylate (R)-4. To achieve chain elongation by two carbons and create a methyl group at the 3-position, (R)-4 was treated with the enolate of dimethyl malonate.…”

Synthesis of all possible stereoisomers of 6,10,13- trimethyltetradecan-2-one, male-produced sex pheromone of Pallantia macunaima

“…3 The reductive removal of the sulfonyl moiety of (5R,6R/S,9S)-6, was achieved smoothly by using magnesium turnings in methanol. 4 Ozonolysis of (6R,10S)-7 and reductive workup gave (4R,8S)-8. The Grignard reagent prepared from (4R,8S)-9 was allowed to react with acetaldehyde, leading to the secondary alcohol, that was submitted to Jones oxidation affording the first isomer (6R,10S).…”

“…4 This compound was then converted into the corresponding tosylate and coupled with isobutylmagnesium bromide in the presence of Li 2 CuCl 4 to afford the alkene (6R,10R)-7. With this compound in hands, we have employed the same reaction sequence described above to prepare the desired isomer (6S,10R)-1.…”