66063-44-3Relevant academic research and scientific papers
Iridoid Sex Pheromone Biosynthesis in Aphids Mimics Iridoid-Producing Plants
Partridge, Suzanne J.,Withall, David M.,Caulfield, John C.,Pickett, John A.,Stockman, Robert A.,Oldham, Neil J.,Birkett, Michael A.
, p. 7231 - 7234 (2021/04/21)
Biosynthesis of (1R,4aS,7S,7aR)-nepetalactol (1) and (4aS,7S,7aR)-nepetalactone (2) in plants involves iridoid synthase (ISY), an atypical reductive cyclase that catalyses the reduction of 8-oxogeranial into the reactive enol of (S)-8-oxocitronellal, and cyclization of this enol intermediate, either non-enzymatically or by a nepetalactol-related short chain dehydrogenase enzyme (NEPS) that yields the nepetalactols. In this study, we investigated the biosynthesis in vivo of 1 and 2 in the pea aphid, Acyrthosiphon pisum, using a library of isotopically-labelled monoterpenoids as molecular probes. Topical application of deuterium-labelled probes synthesized from geraniol and nerol resulted in production of 2H4?lactol 1 and 2H4?lactone 2. However, deuterium incorporation was not evident using labelled probes synthesized from (S)-citronellol. These results suggest that iridoid biosynthesis in animals, specifically aphids, may follow a broadly similar route to that characterised for plants.
Metabolism of geraniol in grape berry mesocarp of Vitis vinifera L. cv. Scheurebe: Demonstration of stereoselective reduction, E/Z-isomerization, oxidation and glycosylation
Luan, Fang,Mosandl, Armin,Muench, Andreas,Wuest, Matthias
, p. 295 - 303 (2008/02/02)
The metabolism of deuterium labeled geraniol in grape mesocarp of Vitis vinifera L. cv. Scheurebe was studied by in vivo-feeding experiments. Stereoselective reduction to (S)-citronellol, E/Z-isomerization to nerol, oxidation to neral/geranial and glycosylation of the corresponding monoterpene alcohols could be demonstrated. Time course studies including the determination of conversion rates revealed that the activity of these secondary transformations of monoterpenes is dependent on the ripening stage and can be distinguished from the development of the primary monoterpene synthase activities by the sharp increase at the end of the ripening period. The stereoselective biosynthesis of the potent odorant cis-(2S,4R)-rose oxide from labeled geraniol in grape berry mesocarp is demonstrated as well. Since (S)-citronellol is the precursor of cis-(2S,4R)-rose oxide it can be concluded that especially the last part of the ripening period is important for the generation of this potent odorant. This finding confirms the conclusion that a higher concentration of flavor compounds could be established in the berries by leaving the fruit on the vine for extended periods.
Regiospecificity and Isotope Effects Associated with the Methyl-Methylene Eliminations in the Enzyme-Catalyzed Biosynthesis of (R)- and (S)-Limonene
Pyun, Hyung-Jung,Coates, Robert M.,Wagschal, Kurt C.,McGeady, Paul,Croteau, Rodney B.
, p. 3998 - 4009 (2007/10/02)
-, -, and geranyldiphosphates (1-t, 1-d4, and 1-d6,t) were synthesized and used as substrates for several monoterpene cyclases to determine the regiospecificity and isotope effects attending the terminating proton transfers in the enzyme-catalyzed biosynthesis of (R)- and (S)-limonene.Degradation of enantiomeric limonenes produced by cyclization of 1-t with the (+)- and (-)-pinene cyclases (synthases) from Salvia officinalis demonstrated that the eliminations occur at both the cis- (55-65percent) and trans-methyl (45-35percent) groups.In contrast, the terminating eliminations in the formation of (+)- and (-)-limonene catalyzed by limonene cyclases from Citrus sinensis and Perilla frutescens, respectively, were shown by degradation to occur exclusively (>/=97-98percent) at the cis terminal methyl group.The intramolecular isotope effects for the methyl-methylene elimination in limonene biosynthesis catalyzed by (+)- and (-)-pinene cyclases from S. officinalis were found to be kH/kD = 2.3 +/- 0.2 and 5.9 +/- 0.5, respectively, by GC/MS determinations of -limonene derived from enzymatic cyclizations of 1-d4.Similar experiments with (-)-limonene cyclase from Mentha spicata resulted in kH/kD = 4.0 +/- 0.4.Incubations of 1-d6,t with pinene and bornyl PP cyclases from S. officinalis exhibited significant remote isotope effects (kH/kD = 1.16-1.27) on the total rate of monoterpene formation which suggest that the initial cyclization step of the enzyme-bound linalyl diphosphate intermediate is an important component of the overall rate of the enzymatic reactions.The isotope effects on the partitioning of the α-terpinyl carbocation intermediate between bicyclization and elimination to limonene were determined from the effects of deuterium substitution on the product ratios derived from enzymatic cyclization of 1-d6,t.The small size of these product isotope effects (kH/kD = 1.2-1.7) is attributed to a conformational inversion of the α-terpinyl ion to a half-chair conformer prior to proton elimination to limonene, thereby rendering the bicyclizations relatively immune to the intrinsic deuterium isotope effect.The regiospecific proton transfers from the cis terminal methyl group effected by the limonene cyclases from Citrus and Perilla are attributed to the minimization of charge seperation in the transition state.
The Cyclisation of Geraniol in Superacids
Carr, Graham,Dean, Christopher,Whittaker, David
, p. 71 - 76 (2007/10/02)
The cyclisation of geraniol (1) in FSO3H-SO2 at -78 deg C to yield the iridoid ether 3β,4α,6aα-trimethyl-cis-perhydrocyclopentafuran was investigated.Decomposition of the ether in FSO3H at room temperature gave the 2-isopropyl-1,3-dimethylcyclopentenium ion, whose structure was confirmed independently.Synthesis of geraniol labelled with deuterium on the gem-dimethyl group and on the single methyl group established the positions of these mehtyls in the iridoid ether.Synthesis of 2-(1-hydroxy-2,2-dimethylcyclopentyl)propan-1-ol established that the ion derived from it did not lie on the reaction pathway.
