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Title: A new cyclohexyl-based chiral auxiliary : application in the total synthesis of (+)-linalool oxide
Author: Al-Hazmi, Ali
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2010
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Abstract:
Seven different racemic cyclohexyl-based chiral auxiliaries (2.4-2.10) were synthesised in moderate to good yields (38-85%) by nucleophilic opening of cyclohexene oxide using carbanions. The racemic cyclohexyl-based chiral auxiliaries were coupled with the 6-methyl-2- methylenehept-5-enoyl chloride (2.20) to form the dienes esters 2.38-2.44. The chiral auxiliarydiene ester adducts 2.38-2.44 were subjected to a comparative study in the permanganatemediated oxidative cyclisation. The best result was obtained by using (±)-trans-2-trityl-1- cyclohexanol ((±)-2.10 (±)-TTC)), resulting in high diastereoselectivity (dr = 97:3) in the resulting THF diols 2.51a/b. The other auxiliaries synthesised gave only moderate to no diastereoinduction. Different methods were used to resolve the racemic auxiliary (±)-TTC including enzymatic resolution and classical resolution. A successful classical resolution was achieved and the enantiomer (–)-TTC was obtained in excellent yield and enantiopurity (99 % ee). The stereochemistry of the obtained enantiomer was defined as (1S,2R) from the X-ray structure of its Mosher ester derivative 2.76. (–)-TTC was used in the total synthesis of (+)-linalool oxide (1.247) which was achieved in 9 steps and 13% overall yield. Finally, nucleophilic additions to α-keto esters containing (±)-TTC were investigated and the preliminary results are described.
Supervisor: Brown, Richard Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.561500  DOI: Not available
Keywords: QD Chemistry
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