bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Structures of Cyclotetradeca‐4,11‐diynone, Cyclotetradeca‐4,11‐diyne‐1,8‐dione, Their Exomethylene Derivatives, and 1,8‐Dioxacyclotetradeca‐4,11‐diyne
Authors: Gleiter Rolf , Ramming Matthias , Weigl Hagen , Wolfart Volker , Irngartinger Hermann , Oeser Thomas 
Published: July 2007

AbstractThe following 14‐membered ring diynes have been synthesized: cyclotetradeca‐4,11‐diynone (4), cyclotetradeca‐4,11‐diyne‐1,8‐dione (6), the corresponding exomethylene derivatives 5 and 7, as well as 1,8‐dioxacyclotetradeca‐4,11‐diyne (8). The synthesis of the diketal of 4 was achieved by the reaction of the ethylene ketal of 1,5‐dibromopentan‐3‐one (9) with the dilithium salt of 1,8‐nonadiyne. Similarly, the diketal of 6 was prepared from the dilithium salt of the ethylene ketal of 1,8‐nonadiyn‐5‐one 11 with 9. The unprotected ketones 4 and 6 were obtained by treating the ketals 10 and 14, respectively, with HCl. The ketones 4 and 6 were transformed to the exomethylene derivatives by a Wittig reaction. The reaction of the dilithium salt of 5‐oxanona‐1,8‐diyne (16a) with 1,5‐dibromo‐3‐oxapentane (15) yielded 8. X‐ray investigations of single crystals of 6 and 8 revealed chair conformations with a zig–zag arrangement, employing two anti orientations of the two chains between the triple bonds. A zig–zag arrangement of the chain containing the carbonyl group was also found in 4. In 3b and 7 Ci symmetry was found, with only one anti conformation in each chain. Molecule 6 crystallizes with C2h symmetry and 8 with a center of symmetry.
Cycloaddition Reactions of 2H‐Benzo[b]thiete and Thiocarbonyl Compounds
Authors: Meier Herbert , Gröschl Dieter , Beckert Rainer , Weiß Dieter 
Published: July 2007

Abstract2H‐Benzo[b]thiete (1) reacts in the o‐quinoid form 1′ with the cyclic trithiocarbonates 4 and 6a, b and with the thioketones 8, 10 and 12 in [8π + 2π] cycloaddition reactions to the spiro compounds 5, 7a, b, 9, 11a, b. Irrespective of the presence of CC double bonds, chemoselective and regioselective addition processes at the CS double bonds take place that lead to 4H‐1,3‐benzodithianes.
Total Synthesis of the Tolypothrix Pentaether from Enantiomerically Pure Homoallyl Alcohols by A Butyrolactone → 1,3‐Diol Strategy
Authors: Weigand Stefan , Brückner Reinhard 
Published: July 2007

AbstractFollowing the retrosynthetic plan of Scheme 1 the permethyl ether 1 from Tolypothrix conglutinata was synthesized from aldehyde 2 and the hydroxylated butyrolactone 3b. Each of these building blocks was obtained from a homoallyl alcohol, i. e. aldehyde 2 from homoallyl alcohol 5 (Scheme 3; 98.1% ee) and lactone 3b from homoallyl alcohol 30 (Schemes 10, 11; 97.7% ee). These alcohols, in turn, stemmed from the Ti(OEt)4/S‐BINOL‐mediated enantioselective addition of the β‐substituted stannane 7 to hexanal (Scheme 3) and the Ti(OEt)4/R‐BINOL‐mediated enantioselective addition of the β‐substituted stannane 31 to aldehyde 32 (Scheme 10), respectively. After O‐methylation of hydroxy lactone 3b (Scheme 11), the resulting methoxy lactone 38 was condensed with aldehyde 2 by Larson's modification of the Peterson olefination to provide the γ‐alkylidene lactone 39 as a 65:35 mixture of Z/E isomers (Scheme 12). Hydrogenation of this mixture gave the cis‐configured γ‐alkyl lactone 40 (Scheme 12). It was accompanied by no more than 5 mol‐% of its trans isomer; this observation seems to imply the occurrence of butenolide 41 as an intermediate of this reaction. An oxidative degradation of lactone 40 via the Criegee rearrangement of a derived peroxonosylate provided the syn‐diol 42 from where another three steps led to the target ether 1 (Scheme 13).
Studies on the Conformation of Boc‐Protected (S)‐(+)‐Isovaline Homopeptide Methyl Esters in the Solid State and in Solution
Authors: Jaun Bernhard , Tanaka Masakazu , Seiler Paul , Kühnle Florian N. M. , Braun Christine , Seebach Dieter 
Published: July 2007

AbstractX‐Ray diffraction analyses of the fully protected peptides Boc‐[(S)‐Iva]n‐OMe (n = 3, 4, 6) reveal two independent molecules in the asymmetric unit. The structures of these can be described as β‐turns or 310 helices (depending on the length of the oligopeptide) of alternating screw sense (M and P) in a head to tail alignment. This structure is stabilized by hydrogen bonds between the NH(1) of the (M)‐helix and the OC(ω‐1) of the (P)‐helix and the NH(2) (M) and the ester carbonyl group (P). Low temperature 1H‐NMR spectra of the hexamer in CD2Cl2 solution show two interchanging species in a ratio of 4:1; NOESY experiments prove that these are the two helical conformers found in the crystal (P:M, 4:1). The NOESY spectrum at −90°C indicates the pairing of (P) and (M) helices. Thermodynamic and kinetic parameters for the helix transformation P ⇌ M (unfolding/folding) are presented.
New cis‐Eudesm‐6‐ene Derivatives from Vetiver Oil
Authors: Weyerstahl Peter , Marschall Helga , Splittgerber Ute , Wolf Dietmar 
Published: July 2007

AbstractThe new cis‐eudesma‐6,11‐diene (1) has been isolated from vetiver oil as a main constituent of the sesquiterpene hydrocarbon fraction. Furthermore, six derivatives [13‐nor‐cis‐eudesm‐6‐en‐11‐one (2), cis‐eudesm‐6‐en‐11‐ol (4), cis‐eudesm‐6‐en‐12‐al (5, 2 epimers), 13‐nor‐cis‐eudesm‐6‐en‐8‐one (6), and cis‐eudesma‐6,11‐dien‐3‐ol (8)] have been identified in the oil. Three of these (2, 4, 5) have been prepared for comparison purposes, e.g. via ozonolysis or hydroboration starting from 1.
Synthesis and Metabolism of the myo‐Inositol Pentakisphosphates
Authors: Rudolf Marco T. , Kaiser Thorsten , Guse Andreas H. , Mayr Georg W. , Schultz Carsten 
Published: July 2007

AbstractAll six isomeric myo‐inositol pentakisphosphates (InsP5), consisting of the two meso compounds myo‐inositol 1,3,4,5,6‐pentakisphosphate [Ins(1,3,4,5,6)P5] (18) and myo‐inositol 1,2,3,4,6‐pentakisphosphate [Ins(1,2,3,4,6)P5] (22) and two pairs of enantiomers myo‐inositol 1,2,4,5,6‐pentakisphosphate [Ins(1,2,4,5,6)P5] (15) myo‐inositol 2,3,4,5,6‐pentakisphosphate [Ins(2,3,4,5,6)P5] (ent‐15) and myo‐inositol 1,2,3,5,6‐pentakisphosphate [Ins(1,2,3,5,6)P5] (20) myo‐inositol 1,2,3,4,5‐pentakisphosphate [Ins(1,2,3,4,5)P5] (ent‐20), respectively, were synthesized. These compounds have been found in tissue, and although not resolved as pure enantiomers, their primary metabolism in a cytosolic extract from fetal calf thymus was therefore investigated by analytical HPLC. Four isomers were dephosphorylated to singly defined inositol tetrakisphosphates, while Ins(1,2,4,5,6)P5 was phosphorylated to myo‐inositol hexakisphosphate (InsP6). Interestingly, Ins(2,3,4,5,6)P5 was the only isomer which was not metabolized. These data demonstrate that chemically synthesized, enantiomerically pure inositol pentakisphosphate isomers are valuable tools for the unravelling of the metabolic pathways of InsP5 turnover in living cells.
Metallated 2‐Alkenyl Sulfoximines in Asymmetric Synthesis: Regio‐ and Stereoselective Synthesis of Highly Substituted Tetrahydrofurans
Authors: Reggelin Michael , Weinberger Heinz , Heinrich Timo 
Published: July 2007

AbstractStarting from the enantiopure 2‐alkenyl sulfoximines 4/5 and epi‐4/5, a one‐pot procedure has been developed for the synthesis of tri‐ and tetrasubstituted tetrahydrofuran derivatives with excellent control of all relevant aspects of their structural description. The cyclization of the intermediate γ‐hydroxyvinyl sulfoximines is strictly regioselective due to the electronic properties of the double bond involved. The absolute configuration at C‐2 can be selected at will by a proper choice of the corresponding lactaldehydes 14 or ent‐14 respectively. The absolute configuration at the 3‐ and 4‐positions of the THF derivatives is under control of the sulfoximine moiety during aldehyde uptake, whereas their relative configuration is fixed due to the 1k relative topicity of attack of the reactands involved in their generation. The configuration at position 5 is determined mainly by the release of 1,3‐allylic strain and is therefore the only stereogenic centre under substrate control. This becomes obvious in two cases (17a and 18a) where stereocontrol at this position is diminished. Here, the absence of a 3‐methyl group as a control element reduces the energetic difference between the Re‐ and the Si‐side attack.
Structure‐odor correlation, XXV. Synthesis and Olfactory Properties of the “Inverse” Megastigmatrienone and Its Analogs
Authors: Weyerstahl Peter , Licha Kai 
Published: July 2007

AbstractThe oxoisophorone monoacetal 2 is a convenient starting material for the synthesis of several megastigmatrienone analogs. Thus, the Wittig reaction of ketone 2, followed by deprotection, led to the dienones 7–10. The “inverse” megastigmatrienone 1 was synthesized from 2 via homologation (→11→12), Grignard reaction (→13) and hydrolysis. The mixture of the four stereoisomers of 1 is dominated by (E,E)‐1. In contrast, (Z,Z)‐1 was obtained as the main product when starting from 2 and proceeding via the reaction sequence →14 →15 →16 →17 and then (Z)‐selective Wittig reaction of aldehyde 17. Likewise, ketoaldehyde 17 is the starting material for the nor derivative 20. The odor evaluation of 1 showed that the typical strong and pleasant tobacco odor of megastigmatrienone D was by no means observed, neither in strength nor in quality. On the other hand, the four stereoisomers of 1 all exhibit a similar weak to moderate odor of floral, sweet, fresh and coumarin‐like tonalities.
One‐Step Synthesis of Functionalized Triptycene‐quinones as Acceptors for Electron‐Transfer Compounds
Authors: Wiehe Arno , Senge Mathias O. , Kurreck Harry 
Published: July 2007

AbstractThe synthesis of appropriate porphyrin‐quinone electron‐transfer complexes as model compounds for photosynthesis requires access to functionalized triptycene quinone aldehydes with different redox potentials. A synthetic strategy involving a classical Diels‐Alder reaction, tautomerization and oxidation was only of limited utility for preparing the desired compounds. Thus, an alternative approach was required and for this purpose a strategy involving the reaction of excess quinone with appropriate anthracene derivatives in acetic acid has been developed. This method affords the target compounds in a single synthetic step in good yields and with high purity. The aldehyde functionality required for the subsequent porphyrin synthesis can be incorporated into either the anthracene or the quinone starting component. Fifteen different triptycene quinones have been synthesized, eight of which have been studied in detail by single crystal X‐ray crystallography to provide insight into their structural chemistry and solid‐state aggregation properties. Additionally, the synthesis of two porphyrin‐quinone target compounds is described.
Structural Aspects of Cyclopropyl Conjugation: Experimental Studies and Ab Initio Calculations
Authors: Haumann Thomas , Boese Roland , Kozhushkov Sergei I. , Rauch Karsten , de Meijere Armin 
Published: July 2007

AbstractLow temperature crystal structural studies of small cyclopropyl‐conjugated unsaturated hydrocarbons reveal significant differences in bond lengths between carbon atoms mainly within the three‐membered rings but also for adjacent CC single bonds. The strongest influence of conjugation was observed for spiro[2.4]hepta‐4,6‐diene (1), where the difference in the lengths of three‐membered ring bonds is 0.050 Å (X‐ray). The same effect is also obvious from ab initio calculations at HF/6‐31G(d) (to a minor extent) and MP2/6‐31G(d) levels, as shown by a difference analysis of bond lengths which was performed in order to cancel out systematic errors and differences for both methods. Static difference electron density maps were derived from the experimental data by multipole refinements. These maps showed shifts of electron density to exocyclic locations within the planes of the three‐membered rings and significant bond ellipticities for the adjacent single bonds. For 1,1‐diethenylcyclopropane (4) a nonsymmetric conformation was found in the crystal lattice, very close to the global minimum structure calculated by ab initio methods.
Oxidation of 4‐Alkyl‐2′‐Hydroxy‐2‐cinnamylideneacetophenones with Thallium(III) Trinitrate: A New Synthesis of (E)‐3‐Styrylchromones
Authors: Silva Artur M. S. , Cavaleiro José A. S. , Elguero José 
Published: July 2007

AbstractThe oxidative rearrangement of (E,E)‐4‐alkyl‐2′‐hydroxy‐2‐cinnamylideneacetophenones 4, obtained by base‐catalysed aldol reaction of 2′‐hydroxyacetophenone and cinnamaldehydes with thallium(III) trinitrate, gave the corresponding 3‐alkyl‐4‐aryl‐1‐(2′‐hydroxyphenyl)‐2‐(dimethoxymethyl)‐3‐buten‐1‐ones. The cyclization of these acetal intermediates with hydrochloric acid gave (E)‐3‐styrylchromones 5. The stereochemistry of the 4‐alkyl‐2′‐hydroxy‐2‐cinnamylidene‐acetophenones 4 and 3‐styrylchromones 5 double bonds was established by NOE experiments.
Unexpected High Temperature Behaviour of 2,2′‐Diethynylbiphenyl in the Gas Phase – a Precursor for Acephenanthrylene Instead of Pyrene
Authors: Sarobe Martin , van Heerbeek Rieko , Jenneskens Leonardus W. , Zwikker Jan W. 
Published: July 2007

AbstractFlash Vacuum Thermolysis (FVT) of 2,2′‐diethynylbiphenyl (6) gave, instead of pyrene (5), acephenanthrylene (10) and fluoranthene (11) as major products. The unequivocal identification of 9‐ethynylphenanthrene (12) at T ⩽ 800 °C suggests that 12 is the initial stable product derived from 6. It is documented that under high‐temperature conditions in the gas phase compound 12 is efficiently converted into 10, which subsequently rearranges to 11. The formation of 12 from 6 is rationalized by invoking the transient formation of cyclobuta[l]phenanthrene (13) by intramolecular cyclization of the ethynyl moieties of 6 followed by a retro‐carbene CH insertion and a 1,2‐H shift. This interpretation is supported by the results of independent FVT of 2,2′‐bis(1‐chloroethenyl)biphenyl (15).
C‐Terminal Incorporation of α‐Trifluoromethyl‐Substituted Amino Acids into Peptides via In‐Situ Deprotection of N‐Teoc Derivatives
Authors: Hollweck Wolfgang , Sewald Norbert , Michel Thomas , Burger Klaus 
Published: July 2007

AbstractA new method for peptide coupling, involving α‐trifluoromethyl substituted amino acids as nucleophiles, proceeds via fluoride catalyzed in situ deprotection and coupling of N‐Teoc protected amino acid esters. A mixed anhydride is thought to be the reaction intermediate.
Synthesis of [7,7‐2H2]epibrassinolide
Authors: Khripach Vladimir A. , Khripach Natalya B. , Zhabinskii Vladimir N. , Zhiburtovich Yuliya Y. , Schneider Bernd , de Groot Aede 
Published: July 2007

AbstractSynthesis of labelled epibrassinolide containing two deuterium atoms in a position which is not subjected to isotopic exchange is reported. Key transformations include preparation of 6,7‐seco steroidal diacid, its cyclization to a cyclic anhydride followed by a regioselective reduction with NaBD4. The obtained [7,7‐2H2]epibrassinolide can be used in biochemical experiments when the loss of isotopic label should be avoided. Copyright © 2007 John Wiley & Sons, Ltd.
Metastatic PEComa arising from renal angiomyolipoma: MRI findings
Authors: El Jack Amr K. , Tomaszewski John E. , Haller Daniel G. , Siegelman Evan S. 
Published: July 2007

AbstractThe perivascular epithelioid cell tumor (PEComa) is a neoplasm composed primarily of HMB‐45‐positive epithelioid cells with a perivascular distribution. Both benign and malignant PEComas have been reported in diverse anatomic locations. We report the MRI features of a metastatic PEComa to the liver that originated within a renal angiomyolipoma (AML). J. Magn. Reson. Imaging 2007;26:159–161. Published 2007 Wiley‐Liss, Inc.
Magnetic resonance imaging and model prediction for thermal ablation of tissue
Authors: Chen Xin , Barkauskas Kestutis J. , Nour Sherif G. , Duerk Jeffrey L. , Abdul‐Karim Fadi W. , Saidel Gerald M. 
Published: July 2007

AbstractPurposeTo monitor and predict tissue temperature distributions and lesion boundaries during thermal ablation by combining MRI and thermal modeling methods.Materials and MethodsRadiofrequency (RF) ablation was conducted in the paraspinal muscles of rabbits with MRI monitoring. A gradient‐recalled echo (GRE) sequence via a 1.5T MRI system provided tissue temperature distribution from the phase images and lesion progression from changes in magnitude images. Post‐ablation GRE estimates of lesion size were compared with post‐ablation T2‐weighted turbo‐spin‐echo (TSE) images and hematoxylin and eosin (H&E)‐stained histological slices. A three‐dimensional (3D) thermal model was used to simulate and predict tissue temperature and lesion size dynamics.ResultsThe lesion area estimated from repeated GRE images remained constant during the post‐heating period when the temperature of the lesion boundary was less than a critical temperature. The final lesion areas estimated from multi‐slice (M/S) GRE, TSE, and histological slices were not statistically different. The model‐simulated tissue temperature distribution and lesion area closely corresponded to the GRE‐based MR measurements throughout the imaging experiment.ConclusionFor normal tissue in vivo, the dynamics of tissue temperature distribution and lesion size during RF thermal ablation can be 1) monitored with GRE phase and magnitude images, and 2) simulated for prediction with a thermal model. J. Magn. Reson. Imaging 2007;26:123–132. © 2007 Wiley‐Liss, Inc.
Image metric‐based correction (autofocusing) of motion artifacts in high‐resolution trabecular bone imaging
Authors: Lin Wei , Ladinsky Glenn A. , Wehrli Felix W. , Song Hee Kwon 
Published: July 2007

AbstractPurposeTo evaluate the performance of the autofocusing (AF) motion correction technique in high‐resolution trabecular bone imaging where image signal‐to noise ratio (SNR) is limited.Materials and MethodsRaw data from 26 clinical three‐dimensional (3D) wrist exams were motion corrected using AF for both in‐plane rotation and translation. Changes in image metrics (a measurement of image sharpness) and structural parameters subsequently computed, were used to gauge the performance of the AF algorithm, and comparisons were made with translation‐only navigator‐corrected results.ResultsOn average, AF generated images with higher image sharpness compared to the navigator echo technique. The average normalized gradient squared (NGS) metric improved by 0.40%, 0.73%, and 0.84%, respectively, following translation‐only navigator, translation‐only AF and combined rotation/translation AF. For all structural parameters, the rotation/translation AF resulted in an approximately two‐fold greater change compared to the navigator technique.ConclusionThe data provide evidence that errors from subtle translational and rotational motion in the structural parameters in high‐resolution trabecular bone images are alleviated by AF and that the resulting improvements are superior to translation‐only 2D navigator correction. J. Magn. Reson. Imaging 2007;26:191–197. © 2007 Wiley‐Liss, Inc.
Noninvasive monitoring of chick development in ovo using a 7T MRI system from day 12 of incubation through to hatching
Authors: Bain Maureen M. , Fagan Andrew J. , Mullin James M. , McNaught Iain , McLean John , Condon Barrie 
Published: July 2007

AbstractPurposeTo determine whether mild cooling of the egg reduces movement to the point where an ultra‐high‐field (7T) MRI system can be used to noninvasively monitor chick growth in ovo from 12 days incubation through to hatching.Materials and MethodsGroup A eggs were incubated at 37.5°C for 21 days. Group B eggs were removed from the incubator on days 12, 15, 17, 18, 19, and 20 of incubation, cooled for one hour, and then returned to the incubator. Group C eggs were cooled as for group B and then individually imaged for 25 minutes using a 7T MRI system before being returned to the incubator. The average size (volume) of the heart, liver, and brain at each stage of incubation was estimated from the T2‐weighted images and compared with existing values in the literature.ResultsThe combination of cooling and MRI significantly reduced chick movement to allow excellent image acquisition at each stage of incubation. Repeated cooling and/or MRI did not significantly slow down or arrest the development of the chicks in either of the experimental groups.ConclusionMRI provides a powerful noninvasive tool to study chick development and the growth of individual organs, including the brain, liver, and heart, in ovo from 12 days' incubation. J. Magn. Reson. Imaging 2007;26:198–201. © 2007 Wiley‐Liss, Inc.
Partial replacement of Fe(o,o‐EDDHA) by humic substances for Fe nutrition and fruit quality of citrus
Authors: Cerdán Mar , Sánchez‐Sánchez Antonio , Juárez Margarita , Sánchez‐Andreu Juan J. , Jordá Juana D. , Bermúdez Dolores 
Published: July 2007

AbstractThe most widely used Iron (Fe) fertilizer in calcareous soils is the synthetic chelate Fe(o,o‐EDDHA). However, humic substances are occasionally combined with Fe chelates in drip irrigation systems in order to lower costs. We investigated the effect of various mixtures of Fe(o,o‐EDDHA) and a commercially available humic substance on Fe availability in a calcareous soil from Murcia, Spain (in vitro experiment) and on leaf Fe content and fruit‐quality attributes of Citrus macrophylla (field experiment). In the in vitro experiment, a calcareous soil was incubated for 15 d with solutions of sole Fe(o,o‐EDDHA) and humic substance and of a mixture of humic substance and Fe(o,o‐EDDHA) to determine the dynamics of available Fe. While the mixture did not significantly increase the available soil Fe, it did decrease the rate of Fe retention in the surface soil compared to sole Fe(o,o‐EDDHA). In the field experiment, the substitution in the application solution of 67% of Fe(o,o‐EDDHA) by commercial humic substance increased leaf P in lemon trees from 0.19% with sole Fe(o,o‐EDDHA) to 0.30% and leaf Fe from 94 mg kg–1 to 115 mg kg–1. Some quality parameters like vitamin C content and peel thickness were also improved with a partial substitution of Fe(o,o‐EDDHA) by humic substances. We conclude that a partial substitution of commercial Fe chelates by humic substance can improve crop Fe uptake and may thus be economically attractive. The underlying physiological mechanisms and ecological implications require further studies.
Modeling nitrate leaching and organic‐C build‐up under semi‐arid cropping conditions of N India
Authors: Mittal Shashi B. , Anlauf Rüdiger , Laik Ranjan , Gupta Atam P. , Kapoor Ashok K. , Dahiya Sunehara S. 
Published: July 2007

AbstractNitrate leaching, overall N balance, and organic‐C build‐up in a semi‐arid agro‐ecosystem in NW India was estimated from the results of a long‐term manurial trial with farmyard manure (FYM) and mineral‐N fertilizer in operation since 1967 at the Research Farm of CCS Haryana Agricultural University, Hisar, India. The model LEACHN was calibrated for the wheat‐growing period November 2000 to April 2001 and the leaching of nitrate during this period was predicted to 48 kg N ha–1without mineral‐N fertilization and 59 kg N ha–1with addition of 120 kg mineral‐N fertilizer, both with the addition of 15 t ha–1FYM. The N balance for the simulation period showed that the 120 kg N ha–1–mineral N fertilization compared to zero mineral N, both plus FYM, resulted in only slightly higher crop uptake, leaching losses, and NH3volatilization, and a negligible increase of N in organic matter. The largest amount remains as an additional build‐up of mineral N in the profile (84.3 kg N ha–1) which is prone to losses as ammonia or nitrate.The model was used to simulate organic‐C build‐up with FYM and a decrease of organic C without FYM for a period of 33 y (1967–2000). The simulated C build‐up to about 0.1 g kg–1agreed very well with the measured values and showed that additional mineral‐N fertilization will not have any significant effect on organic‐C content. Simulations with the assumption of no FYM application showed a gradual decrease of organic C from its starting value of 0.046 g kg–1in 1967 down to almost half of this. This agreed well with the observed organic‐C values of 0.028 g kg–1as measured for unmanured plots.