On the Stereochemistry of Irones

Rautenstrauch, Valentin; Willhalm, B.; Thommen, Walter; Ohloff, G.

doi:10.1002/hlca.19840670139

Cited by 44 publications

(29 citation statements)

References 21 publications

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“…As previously reported [7], the irones are found with (2S,6R, cis)-and (2R,6R, trans) configuration, and from a different source the (2R,6S, cis) compounds were isolated [S]. As shown in Scheme 4, the cis geometry derives from the methylation of the thermodynamically favoured chair form of the terpenoid side chain, whereas the boat form leads to the trans products which, consequently, are present in smaller quantities.…”

Section: Fig 1 Hplc Separation (Rpsupporting

confidence: 73%

Studies on the Biosynthesis of Iridals and Cycloiridals

Marner¹,

Gladtke²,

Jaenicke³

1988

Helvetica Chimica Acta

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The incorporation of [2-I4C]acetate, [2-14C]mevalonate, and [3H]squalene proved the squalenoid nature of the iridals, novel triterpenoids from rhizomes of swordlilies. Methionine is readily incorporated into cycloiridals of Iris pullida dalrnatica, thus indicating that the methylation of iridals via S-adenosyl-L-methionine leads to the formation of the irone moiety of the bicyclic compounds. The 3H/'4C ratio of the transferred labelled methyl group remained unchanged. Therefore, the methylation/cyclization of the terpenoid side chain of iridals must proceed by a concerted mechanism without formation of a cyclopropanoid intermediate.Introduction. -The precursors of the irones 1 and 2, the odoriferous principle of the 'essence d'iris', belong to a new class of triterpenoids [l-31 which we named iridals [4]. There are several such compounds in extracts of the plants, mainly distinguished by their degree of unsaturation or hydroxylation. The iridals usually have in common 30 Catoms, one highly substituted cyclohexane ring (ring B), and a terpenoid non-cyclic (EE)-homofarnesyl side chain [4]. Some typical structures are depicted in Scheme 1. In the irone precursors, the cycloiridals (see 5 and 6), however, as a new structural feature, the unsaturated side chain is cyclized and the resulting ring system ('E' ring) is substituted by an additional CH, group [2]. There are no cycloiridals with an ionone ring and only 30 C-atoms. This makes it plausible that the formation of the cycloiridals is initiated by the addition of an active CH, group to the terminal double bond of iridals. To validate this assumption, experiments on the biosynthesis of iridals and cycloiridals were undertaken.We describe here our investigations on the squalenoid origin of the iridals and of their methylation by feeding labelled precursors to young Iris plantlets. By these experiments, the question was answered if the cyclization to ring E proceeds by an epimethylene intermediate, analogous to the epoxide start of lanosterol biosynthesis, or as a concerted process initiated by a CH: ion, in parallel to the proton-triggered cyclization of squalene in the hopane series.

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Section: Fig 1 Hplc Separation (Rpsupporting

confidence: 73%

Studies on the Biosynthesis of Iridals and Cycloiridals

Marner¹,

Gladtke²,

Jaenicke³

1988

Helvetica Chimica Acta

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“…The MS data obtained here for pinonaldehyde were in accordance with those of ref. [12]. 2,2,3-trimethylcyclobutyl-1-ethanone was prepared as previously described [12] starting from pinonaldehyde synthesized as described above.…”

Section: Chemicalsmentioning

confidence: 99%

“…[12]. 2,2,3-trimethylcyclobutyl-1-ethanone was prepared as previously described [12] starting from pinonaldehyde synthesized as described above. Other chemicals used in this study were all com-…”

Section: Chemicalsmentioning

confidence: 99%

Kinetic study of gas-phase reactions of pinonaldehyde and structurally related compounds

Glasius

Calogirou

Jensen

et al. 1997

Int. J. Chem. Kinet.

108

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Rate constants for the reactions of OH, NO 3 , and O 3 with pinonaldehyde and the structurally related compounds 3-methylbutanal, 3-methylbutan-2-one, cyclobutylmethylketone, and 2,2,3-trimethyl-cyclobutyl-1-ethanone have been measured at using on-line Fourier transform infrared spectroscopy. The rate constants obtained for the reactions with pinonaldehyde were: , , and cm 3 mole-. The results obtained indicate a chemical lifetime of pinonaldehyde in the troposphere of about two hours under typical daytime conditions, .

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“…The standard racemate of trans-g-irone was not available in our laboratory: this isomer has seldom been found in iris oil, and only in trace amount. 33 cis-and trans-a-Irone, b-irone and cis-g-irone can be separated with a 50% EtTBS-g-CDD/PS-086 column. With this CDD/polysiloxane combination, one trans-a-irone enantiomer coelutes with one cis-g-irone enantiomer: an unequivocal ee determination of these components in iris oil can again be obtained with MDGC.…”

Section: Y17mentioning

confidence: 99%

Cyclodextrin Derivatives in GC Separation of Racemic Mixtures of Volatiles. Part XI. Some Applications of Cyclodextrin Derivatives in GC Enantioseparations of Essential Oil Components

et al. 1997

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Cyclodextrin derivatives (CDDs) are successful GC enantioselective stationary phases to evaluate essential oils through the enantiomeric composition of their optically active components. The most recent CDDs have greatly enlarged the number of separable racemates and, in many cases, it is now possible to evaluate origin and genuineness of an essential oil through several of its optically active components in a single GC run. Applications of this approach to lavender, lemon, peppermint, rose and iris oils are here described.

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On the Stereochemistry of Irones

Cited by 44 publications

References 21 publications

Studies on the Biosynthesis of Iridals and Cycloiridals

Studies on the Biosynthesis of Iridals and Cycloiridals

Kinetic study of gas-phase reactions of pinonaldehyde and structurally related compounds

Cyclodextrin Derivatives in GC Separation of Racemic Mixtures of Volatiles. Part XI. Some Applications of Cyclodextrin Derivatives in GC Enantioseparations of Essential Oil Components

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