title: A practical chemo-enzymatic approach to highly enantio-enriched 10-ethyl-7,8-dihydro-γ-ionone isomers: a method for the synthesis of 4,5-didehydro-α-ionone.
abstract: An efficient and convenient strategy for the enantioselective synthesis of enantiomerically enriched 10-ethyl-7,8-dihydro-γ-ionone isomers (R)-(+)-7, and (S)-(-)-7 are described utilizing a lipase mediated resolution protocol, and reductive elimination of the secondary allylic alcohol as the key step. The enantioselective and diastereoselective lipase kinetic acetylation of 4-hydroxy-γ-ionone derivatives 6a afforded the 4-acetyl-γ-ionone derivatives (-)-8, and the 4-hydrox-γ-ionone derivatives (+)-6a, which are suitable precursors of the desired products. Stereospecific palladium-mediated elimination of allylic acetate provides the target compounds with an excellent enantiomeric excess and yield. Additionally, the novel 4,5-didehydro-α-ionone 13 is obtained from readily prepared (2,6,6-trimethylcyclohexa-2,4-dien-1-yl) methanol 9. The structures of all newly synthesized compounds have been elucidated by (1)H, (13)C NMR, GC-MS, and IR spectrometry. These compounds represent a new class of odorants that may be of pivotal relevance in industrial perfumery.
authors: Department of Chemistry, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors: Assem
authors: 0000-0002-7885-3201
authors: A
authors: Barakat
authors: Department of Chemistry, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors: Abdullah M
authors: AM
authors: Al-Majid
authors: Department of Chemistry, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors: Yahia Nasser
authors: 0000-0002-9762-0323
authors: YN
authors: Mabkhot
authors: Department of Chemistry, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors: Zeid A
authors: ZA
authors: Al-Othman
mesh_terms: D007536:Isomerism; D008049:Lipase / Q000378:metabolism; D045792:Norisoprenoids / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D011549:Pseudomonas / Q000201:enzymology
chemical_list: D045792:Norisoprenoids; D008049:Lipase; C011879:alpha-ionone