Eine einfache Synthese der enantiomeren ( E )‐9‐Hydroxy‐2‐decensäuren

Simple Synthesis of the Enantiomeric ( E )‐9‐Hydroxy‐2‐decenoic Acids The enantiomeric ( E )‐9‐Hydroxy‐2‐decenoic acids ( 1 ), components of the swarm settling pheromone in Apis mellifica L. (honey bee) have been synthesized. The lithium derivative of 1‐hexyne was treated with ( R )‐(+)‐methyloxirane ( 2 ), ( S )‐(−)‐ 2 or (±)‐ 2 to give the alkynols ( R )‐(−)‐ 3 , ( S )‐(+)‐ 3 or (±)‐ 3 , which could be isomerized with the sodium salt of 1,3‐propanediamine to give ( R )‐(−)‐8‐nonyn‐2‐ol ( 4 ) and (±)‐ 4 . These were methoxycarbonylated to produce the esters ( R )‐(−) ‐5 , ( S )‐(+) ‐5 or (±) ‐5 . Selective hydrogenation in pyridine with Pd/BaSO 4 as catalyst gave the (Z)‐esters ( R )‐(−) ‐6 , ( S )‐(+) ‐6 or (±) ‐6 which could be isomerized with photochemically generated phenylthio radicals to produce the ( E )‐esters ( R )‐(–) ‐7 , ( S )‐(+) ‐7 or (±) ‐7 . The acids present in the pheromone ( R )‐(−) ‐1 , ( S )‐(+) ‐1 and (±) ‐1 could be obtained by basic hydrolysis of the esters. The minor but important component 8 of the swarm settling pheromone has been synthesized by treating the Grignard reagent obtained from 5‐bromo‐guaiacol benzyl ether with ethylene oxide to give 9 in high yield. Hydrogenolytic removal of the benzyl group in 9 produced 8 directly.