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Upstream product

• 645-68-1 pseudoirone 
• 52567-96-1 3,6,7-trimethyl-oct-6-en-1-yn-3-ol 
• 3899-32-9 (E)-3,6,7-trimethylocta-2,6-dien-1-ol 
• 58307-67-8 3,6,7-trimethyl-6-octen-1-en-3-ol 
• 72074-86-3 (+-)-4t-(2,5t,6,6-Tetramethyl-cyclohex-2-en-r-yl)-but-3-en-2-on 
• 917-54-4 methyllithium 
• 108032-55-9 (E/Z)-(4S,6R)-(1,4,5,5-Tetramethyl-1-cyclohexen-6-yl)acrylonitrile 
• 153061-00-8 (-)-(5S)-2,5,6,6-tetramethylcyclohex-1-ene-1-carbaldehyde 
• 67-64-1 acetone 
• 140632-38-8 (+)-(3R,7S)-4,7,8,8-tetramethyl-1-oxaspiro<2.5>oct-4-ene 
• 260257-26-9 (+)-(2S,4S,5R,6S)-4,5-epoxy-4,5-dihydro-α-irone 
• 202481-73-0 4-(2,5,6,6-tetramethyl-2-cyclohexen-1-yl)-3-buten-2-one 
• 139406-58-9 (E)-3-((1R,5S)-2,5,6,6-Tetramethyl-cyclohex-2-enyl)-acrylic acid 
• 127075-63-2 acetic acid-(2,2,4-trimethyl-cyclohex-3-enylmethyl ester) 

Relevant academic research and scientific papers

Enantioselective divergent synthesis of (-)-cis-a- And (-)-cis-g-irone by using wilkinson's catalyst

A simple, efficient synthesis is reported for (-)-cis-a-and (-)-cis-g-irone, two precious constituents of iris oils, in ≥99% diastereomeric and enantioselective ratios. The two routes diverge from a common intermediate prepared from (-)-epoxygeraniol. Of general interest in this approach is the installation of the enone moiety of irones through a NHC-AuI-catalyzed Meyer-Schuster-like rearrangement of a propargylic benzoate and the use of Wilkinson's catalyst for the stereoselective hydrogenation of a prostereogenic exocyclic double bond to secure the critical cis stereochemistry of the alkyl groups at C2 and C6 of the irones. The stereochemical aspects of this reaction are rationally supported by DFT calculation of the conformers of the substrates undergoing the hydrogenation and by a modeling study of the geometry of the rhodium ν2 complexes involved in the diastereodifferentiation of the double bond faces. Thus, computational investigation of the ν2 intermediates formed in the catalytic cycle of prostereogenic alkene hydrogenation by using Wilkinson's catalyst could be highly predictive of the stereochemistry of the products.

Enzyme-Mediated Preparation of (+)- and (-)-β-Irone and (+)- and (-)-cis-γ-Irone from Irone alpha

The (-)- and (+)-β-irones ((-)- and (+)-2, resp.), contaminated with ca. 7-9 percent of the (+)- and (-)-trans-α-isomer, respectively, were obtained from racemic α-irone via the 2,6-trans-epoxide (+/-)-4 (Scheme 2). Relevant steps in the sequence were the LiAlH4 reduction of the latter, to provide the diastereoisomeric-4,5-dihydro-5-hydroxy-trans-α-irols (+/-)-6 and (+/-)-7, resolved into the enantiomers by lipase-PS-mediated acetylation with vinyl acetate. The enantiomerically pure allylic acetate esters (+)- and (-)-8 and (+)- and (-)-9, upon treatment with POCl3/pyridine, were converted to the β-irol acetate derivatives (+)- and (-)-10, and (+)- and (-)-11, respectively, eventually providing the desired ketones (+)- and (-)-2 by base hydrolysis and MnO2 oxidation. The 2,6-cis-epoxide (+/-)-5 provided the 4,5-dihydro-4-hydroxy-cis-α-irols (+/-)-13 and (+/-)14 in a 3:1 mixture with the isomeric 5-hydroxy derivatives (+/-)-15 and (+/-)-16 on hydride treatment (Scheme 1). The POCl3/pyridine treatment of the enantiomerically pure allylic acetate esters, obtained by enzymic resolution of (+/-)-13 and (+/-)-14, provided enantiomerically pure cis-α-irol acetate esters, from which ketones (+)- and (-)-22 were prepared (Scheme 4). The same materials were obtained from the (9S) alcohols (+)-13 and (-)-14, treated first with MnO2, then with POCl3/pyridine (Scheme 4). Conversely, the dehydration with POCl3/pyridine of the enantiomerically pure 2,6-cis-5-hydroxy derivatives obtained from (+/-)-15 and (+/-)-16 gave rise to a mixture in which the γ-irol acetates 25a and 25b and 26a and 26b prevailed over the α- and β-isomers (Scheme 5). The (+)- and (-)-cis-γ-irones ((+)- and (-)-3, resp.) were obtained from the latter mixture by a sequence involving as the key step the photochemical isomerization of the α-double bond to the γ-double bond. External panel olfactory evaluation assigned to (+)-β-irone ((+)-2) and to (-)-cis-γ-irone ((-)-3) the strongest character and the possibility to be used as dry-down note.

Synthesis of both enantiomers of cis-α-irone and cis-γ-irone, principal constituents of iris oil, via resolution of (±)-2,2,4-trimethyl-3-cyclohexene-1-carboxylic acid

The principal constituents of iris oil, (-)-cis-α-irone and (-)-cis-γ-irone, and their enantiomers, were synthesized from (-)- and (+)-2,2,4-trimethyl-3-cyclohexene-1-carboxylic acids. The racemic acid was resolved by recrystallization of its salt with a chiral amine, or by enzymatic hydrolysis of the corresponding alcohol. The fragrances of (-)-(1R,5S)-cis-α-irone and (-)-(1R,5S)-cis-γ-irone were superior to those of (+)-(1S,5R)-cis-α-irone and (+)-(1S,5R)-cis-γ-irone. Copyright (C) 2000 Elsevier Science Ltd.

Acetylation of racemic cis- and trans-α-irols, mediated by Porcine Pancreatic Lipase (PPL) - A new route to (-) and (+)-cis-α-irone

The mixture of the four racemic stereoisomers of α-irol (5-8) was submitted to PPL-mediated acetylation; cis-α-irol 8b was converted more quickly than any other diastereoisomer and in enantiopure fashion. By chance, this latter derivative was the precursor of (-)-cis-α-irone, the stereoisomer showing the strongest Orris butter character. Suitable manipulation of the material left changed by PPL provided (+)-cis-α-irone. PPL's mode of transformation of epoxy trans- and cis-α-irols was investigated, in order to ascertain the effect of chemical structure on the discriminating properties of this enzyme.

Enzyme-mediated preparation of (+)- and (-)-cis-α-irone and (+)- and (- )-trans-α-irone

The preparation of (-)- and (+)-trans-α-irone (1a and 1b, resp.) and of (+)- and (-)-cis-α-irone (1c and 1d, resp.) from commercially available Irone alpha is reported. The relevant step in the synthetic sequence is the initial chromatographic separation

Preparation of Optically Active Flowery and Woody-Like Odorant Ketones via Corey-Chaykovsky Oxiranylation: Irones and Analogues

α-, β-, and γ-Irones and analogues have been prepared from optically active (+)-1, (+)-6a,b, and (+)-17, via a Corey-Chaykovsky oxiranylation (Me2S, Me2SO4, Me2SO, NaOH) followed by isomerisation (SnCl4 or MgBr2). (+)-Dihydrocyclocitral (19a), obtained from (-)-citronellal, and analogue (+)-19b, were condensed with various ketones to afford (+)-21a-f, and after hydrogenation (+)-22a-f.A mild oxidative degradation of aldehydes (+)-trans- and (-)-cis-8a,b to ketones (-)-16a,b, as well as olfactive evaluations, 13C-NMR assignments, and absolute configurations of the intermediate epoxides, aldehydes, and alcohols are presented.

Synthesis of (+)- and (-)-cis-α-irones

A stereocontrolled total synthesis of natural (+)-cis-α-irone (1) is described. The key intermediate (+)-hemiacetal 15 was prepared from the diene 10 in six steps. The crucial optical resolution of (+)-15 was achieved by initial stereoselective conversion into the corresponding l-menthyl acetals 16 and 17 followed by separation and hydrolysis. One of the optically pure enantiomers of 15 was transformed to (-)-18 and then to (+)-1 in seven steps. The synthetic (+)-1 was found to be identical with the natural (+)-cis-α-irone. The isomeric (-)-cis-α-irone was also synthesized from the other enantiomer of 15, via (+)-18.

38. On The Stereochemistry of the Irones

In view of the demonstration by Jaenicke et al. that different Iris varieties produce enantiomeric irones , we complement our 1971 paper on the stereochemistry of the irones .1) We give what information we have on the origin of the Iris oil used in