- A cascade aerobic epoxidation of alkenes over Au/CeO2 and Ti-mesoporous material by "in situ" formed peroxides
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The one-pot epoxidation of alkenes with O2 is performed with nano-particulated Au/CeO2 and Ti-MCM-41 silylated materials in the presence of a hydrocarbon and azobis-iso-butyronitrile (AIBN) as a promoter. This initiator is able to fo
- Aprile, Carmela,Corma, Avelino,Domine, Marcelo E.,Garcia, Hermenegildo,Mitchell, Chris
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Read Online
- Bovine liver acetone powder (BLAP) catalyzed synthesis of chiral C-8 allyl alcohols: An application of substrate specificity approach
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(S)-Matsutake alcohol is synthesized by enzymatic hydrolysis in 92% optical purity using bovine liver acetone powder (BLAP). The principle of substrate specificity approach is applied to the synthesis of C-8 allyl alcohols in 46-93% enantiomeric purities using BLAP.
- Basavaiah,Bhaskar Raju
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Read Online
- Reductive deprotection of silyl groups with Wilkinson's catalyst/catechol borane
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Traditionally silyl groups are deprotected with acids and fluorides. These methods are, however, less discriminating when multi-silyl groups are present in the same molecule, resulting in lower yields of the desired products. The manipulation of these functions during the total synthesis of natural products, for example, prostaglandins and isoprostanes, requires the selective protection and deprotection of these groups. We are reporting here on a mild, selective and efficient method for the reductive deprotection of silyl groups using Wilkinson's catalyst/catechol borane or catechol borane alone.
- Patel, Pranav,Chang, Chih-Tsung,Kang, Namin,Lee, Gue-Jae,Powell, William S.,Rokach, Joshua
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Read Online
- [Pd]-Catalyzedpara-selective allylation of phenols: access to 4-[(E)-3-aryl/alkylprop-2-enyl]phenols
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4-[(E)-3-Arylprop-2-enyl]phenols are omnipresent scaffolds and constitute natural products and biologically significant compounds. Obtusastyrene and obtustyrene are two such phenolic-based natural products isolated fromDalbergia retusa. The development of strategies based on a site-selective allylation, particularly protecting group-free substrates and non-activated coupling agents, is indispensable in organic synthesis. Herein, we present a highly regioselective [Pd]-catalyzedpara-allylation of phenols using simple, inactivated allylic alcohols as allylating coupling partners. Notably, this strategy is successful in open-air and under mild reaction conditions. Besides, the efficacy of the present protocol was demonstrated by the direct synthesis of obtusastyrene and obtustyrene.
- Chinnabattigalla, Sreenivasulu,Choudhury, Aditya,Gedu, Satyanarayana
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supporting information
p. 8259 - 8263
(2021/10/12)
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- Pickering-Droplet-Derived MOF Microreactors for Continuous-Flow Biocatalysis with Size Selectivity
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Enzymatic microarchitectures with spatially controlled reactivity, engineered molecular sieving ability, favorable interior environment, and industrial productivity show great potential in synthetic protocellular systems and practical biotechnology, but their construction remains a significant challenge. Here, we proposed a Pickering emulsion interface-directed synthesis method to fabricate such a microreactor, in which a robust and defect-free MOF layer was grown around silica emulsifier stabilized droplet surfaces. The compartmentalized interior droplets can provide a biomimetic microenvironment to host free enzymes, while the outer MOF layer secludes active species from the surroundings and endows the microreactor with size-selective permeability. Impressively, the thus-designed enzymatic microreactor exhibited excellent size selectivity and long-term stability, as demonstrated by a 1000 h continuous-flow reaction, while affording completely equal enantioselectivities to the free enzyme counterpart. Moreover, the catalytic efficiency of such enzymatic microreactors was conveniently regulated through engineering of the type or thickness of the outer MOF layer or interior environments for the enzymes, highlighting their superior customized specialties. This study provides new opportunities in designing MOF-based artificial cellular microreactors for practical applications.
- Liang, Linfeng,Shi, Hu,Tian, Danping,Wang, Jun-Hao,Xue, Nan,Yang, Hengquan,Zhang, Xiaoming
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supporting information
p. 16641 - 16652
(2021/10/20)
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- Concise, scalable and enantioselective total synthesis of prostaglandins
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Prostaglandins are among the most important natural isolates owing to their broad range of bioactivities and unique structures. However, current methods for the synthesis of prostaglandins suffer from low yields and lengthy steps. Here, we report a practicability-oriented synthetic strategy for the enantioselective and divergent synthesis of prostaglandins. In this approach, the multiply substituted five-membered rings in prostaglandins were constructed via the key enyne cycloisomerization with excellent selectivity (>20:1 d.r., 98% e.e.). The crucial chiral centre on the scaffold of the prostaglandins was installed using the asymmetric hydrogenation method (up to 98% yield and 98% e.e.). From our versatile common intermediates, a series of prostaglandins and related drugs could be produced in two steps, and fluprostenol could be prepared on a 20-gram scale. [Figure not available: see fulltext.]
- Zhang, Fuhao,Zeng, Jingwen,Gao, Mohan,Wang, Linzhou,Chen, Gen-Qiang,Lu, Yixin,Zhang, Xumu
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p. 692 - 697
(2021/06/01)
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- Visible-Light Photoredox-Catalyzed α-Regioselective Conjugate Addition of Allyl Groups to Activated Alkenes
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The α-regioselective conjugate addition of allyl groups to activated alkenes is a poorly explored area of research. Herein, we report an α-adduct and (E)-isomer selective conjugate addition of allylsilanes to activated alkenes by visible-light photoredox catalysis. The reaction involves allylic radicals that can be generated from allylsilanes through a photoinduced single-electron transfer mechanism. (Figure presented.).
- Gontala, Arjun,Woo, Sang Kook
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supporting information
p. 3223 - 3228
(2020/07/06)
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- Palladium-catalyzed regioselective synthesis of B(4,5)-or B(4)-substituted: O-carboranes containing α,β-unsaturated carbonyls
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With the help of a carboxylic acid directing group, Pd-catalyzed regioselective synthesis of B(4,5)-or B(4)-substituted o-carboranes containing α,β-unsaturated carbonyls has been reported. The-COOH, removed during the course of the reaction, is responsible for controlling the regioselectivity. The desired products could be obtained in moderate to good yields.
- Li, Jiaoyi,Lu, Jian,Tian, Song,Wang, Qian,Zhang, Chuyi,Zhang, Jianwei,Zhou, Ling
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supporting information
p. 4723 - 4727
(2020/07/13)
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- Chemoselective Oxidation of p-Methoxybenzyl Ethers by an Electronically Tuned Nitroxyl Radical Catalyst
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The oxidation of p-methoxy benzyl (PMB) ethers was achieved using nitroxyl radical catalyst 1, which contains electron-withdrawing ester groups adjacent to the nitroxyl group. The oxidative deprotection of the PMB moieties on the hydroxy groups was observed upon treatment of 1 with 1 equiv of the co-oxidant phenyl iodonium bis(trifluoroacetate) (PIFA). The corresponding carbonyl compounds were obtained by treating the PMB-protected alcohols with 1 and an excess of PIFA.
- Hamada, Shohei,Sugimoto, Koichi,Elboray, Elghareeb E.,Kawabata, Takeo,Furuta, Takumi
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supporting information
p. 5486 - 5490
(2020/07/24)
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- Effects of a forming process on the properties and structure of RANEY-Ni catalysts for the hydrogenation of 1,4-butenediol
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Three commercial Ni-Al alloys formed by a vacuum atomization method (NAV), atmospheric atomization method (NAA) and high-temperature melting method (NAH) were leached by 10 wt% NaOH solution to prepare three RANEY-Ni catalysts (RNAV, RNAA and RNAH, correspondingly). The effects of a forming process on the structure of Ni-Al alloys and the corresponding RANEY-Ni catalysts were investigated via XRD, XPS, SEM, TEM, NH3-TPD, N2 adsorption-desorption and EDX-mapping studies. Also, the as-prepared RANEY-Ni catalysts were evaluated via the hydrogenation of 1,4-butenediol (BED) to produce 1,4-butanediol (BDO). The results showed that the specific surface areas and surface morphologies of the Ni-Al alloys present significant differences. Meanwhile, the RNAA sample presented a comparatively regular morphology, similar to a small piece of sugar cane. The weak and medium acid peak areas of the RNAA catalyst were lower than those of the other samples. RNAV showed higher weak and medium acid peak areas, demonstrating the higher number of acid centers on the surface of the catalyst. The surface of the RNAA catalyst obtained from NAA contained more active component-Ni, about 90 wt% on the surface, and the specific surface area of the sample was 75 times that of its precursor Ni-Al alloy powder (NAA). The evaluation results present that the RNAA catalyst shows better hydrogenation performance, with BED conversion of 100%, both BDO selectivity and yield of 46.11%.
- Fan, Xing,Gao, Xianlong,Ma, Fengyun,Mo, Wenlong,Noritatsu, Tsubaki,Wu, Hongli
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p. 5516 - 5524
(2020/02/22)
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- Metathesis at an Implausible Site: A Formal Total Synthesis of Rhizoxin D
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The new approach to the anticancer agent rhizoxin D described herein does not cohere with the conventional logic of metathesis, according to which macrocycles are best closed at a disubstituted olefinic site; rather, the trisubstituted C11?C12 alkene flanked by an allylic -OH group served as the pivot point for synthesis. This motif was attained in good yield and excellent selectivity by a sequence of alkyne metathesis, trans-hydrostannation and cross coupling. Because the exact same substructure is prominently featured in numerous other natural products, the underpinning strategy, though unusual, might bear more general relevance.
- Karier, Pol,Ungeheuer, Felix,Ahlers, Andreas,Anderl, Felix,Wille, Christian,Fürstner, Alois
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supporting information
p. 248 - 253
(2018/12/13)
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- A General One-Pot Methodology for the Preparation of Mono- and Bimetallic Nanoparticles Supported on Carbon Nanotubes: Application in the Semi-hydrogenation of Alkynes and Acetylene
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A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N-heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one-pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi-hydrogenation of acetylene in industrially relevant acetylene/ethylene-rich model gas feeds and showed excellent stability even after 40 h of reaction.
- Lomelí-Rosales, Diego A.,Delgado, Jorge A.,Díaz de los Bernardos, Miriam,Pérez-Rodríguez, Sara,Gual, Aitor,Claver, Carmen,Godard, Cyril
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supporting information
p. 8321 - 8331
(2019/06/04)
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- Manganese-Catalyzed Ring-Opening Coupling Reactions of Cyclopropanols with Enones
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A manganese-catalyzed ring-opening coupling reaction of cyclopropanols with enones for the facile and efficient preparation of 1,6-diketones is described. A wide array of synthetically important 1,6-diketones bearing manifold functional groups are obtained with up to 93% yield. These reactions feature broad substrate scopes, environmentally benign conditions, inexpensive catalyst, and operational simplicity.
- Zhang, Yong-Hui,Zhang, Wen-Wei,Zhang, Ze-Yu,Zhao, Kai,Loh, Teck-Peng
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supporting information
p. 5101 - 5105
(2019/07/03)
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- Total synthesis of PGF2α and 6,15-diketo-PGF1α and formal synthesis of 6-keto-PGF1α via three-component coupling
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The asymmetric total synthesis of PGF2α and 6,15-diketo-PGF1α and formal synthesis of 6-keto-PGF1α from a common key intermediate are described. The key intermediate, which has a chiral cyclopentane backbone possessing suitable functional groups with required stereochemistry for both side chains, was prepared from (R)-4-silyloxy-2-cyclopentenone through a three-component coupling reaction. The Wittig reaction, Nozaki-Hiyama-Kishi (NHK) coupling and cross metathesis completed the synthesis of PGF2α, 6,15-diketo-PGF1α and 6-keto-PGF1α.
- Kim, Taehyeong,Lee, Sung Il,Kim, Sejin,Shim, Su Yong,Ryu, Do Hyun
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- Selective Deprotection of the Diphenylmethylsilyl (DPMS) Hydroxyl Protecting Group under Environmentally Responsible, Aqueous Conditions
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Two new methods for selective deprotection of diphenylmethylsilyl (DPMS) ethers are described. Unmasking can be achieved with either catalytic amounts of perfluoro-1-butanesulfonyl fluoride (a SuFEx reagent) under mild, aqueous micellar conditions, or using stoichiometric amounts of 18-crown-6 ether in aqueous ethanol.
- Akporji, Nnamdi,Lieberman, Josh,Maser, Michael,Yoshimura, Masahiko,Boskovic, Zarko,Lipshutz, Bruce H.
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p. 5743 - 5747
(2019/11/11)
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- Microwave-assisted isomerizations of epoxides to allylic alcohols
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The present work reports a study on the isomerization reactions of several alkyl epoxides to the corresponding allylic alcohols or bicyclic alcohols under microwave irradiation. The reaction occurred in the presence of lithium diisopropylamide as a base and different experimental conditions in terms of solvent, amount of the base, times and temperatures. The traditional heating with an oil-bath and the use of alternative organometallic bases, as the Lochmann-Schlosser bases, have been furthermore compared with the microwave heating. The results obtained show that the use of microwave irradiations on promoting the isomerization of epoxides gives access to a series of synthetically useful products, among which allylic alcohols and bicyclic alcohols, depending on the starting substrate.
- Consiglio, Gabriella Barozzino,Mordini, Alessandro
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p. 447 - 454
(2018/05/22)
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- Enantioselective addition of selenosulfonates to α,β-unsaturated ketones
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An organo-catalyzed enantioselective addition of selenosulfonates to α,β-unsaturated ketones was developed for the first time. With a chiral squaramide as an efficient catalyst, the desired α-selenylated ketones were obtained in a good yields with high enantioselectivity up to 89% ee, and good results could be obtained on a gram scale. The products could also be efficiently transformed into useful building blocks with a propenylic stereocenter; the strategy presented in this study may find further applications in organic synthesis.
- Luo, Shilong,Zhang, Nan,Wang, Zhen,Yan, Hailong
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supporting information
p. 2893 - 2901
(2018/05/03)
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- Ruthenium(II)-Catalyzed Regio- and Stereoselective C-H Allylation of Indoles with Allyl Alcohols
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A ruthenium-catalyzed C-H allylation of indoles with allyl alcohols via β-hydroxide elimination is reported. Without external oxidants and expensive additives, this reaction features mild reaction conditions, compatibility with various functional groups, and good to excellent regioselectivity and stereoselectivity.
- Wu, Xiaowei,Ji, Haitao
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supporting information
p. 2224 - 2227
(2018/04/30)
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- One-Step Bioconversion of Fatty Acids into C8-C9 Volatile Aroma Compounds by a Multifunctional Lipoxygenase Cloned from Pyropia haitanensis
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The multifunctional lipoxygenase PhLOX cloned from Pyropia haitanensis was expressed in Escherichia coli with 24.4 mg·L-1 yield. PhLOX could catalyze the one-step bioconversion of C18-C22 fatty acids into C8-C9 volatile organic compounds (VOCs), displaying higher catalytic efficiency for eicosenoic and docosenoic acids than for octadecenoic acids. C20:5 was the most suitable substrate among the tested fatty acids. The C8-C9 VOCs were generated in good yields from fatty acids, e.g., 2E-nonenal from C20:4, and 2E,6Z-nonadienal from C20:5. Hydrolyzed oils were also tested as substrates. The reactions mainly generated 2E,4E-pentadienal, 2E-octenal, and 2E,4E-octadienal from hydrolyzed sunflower seed oil, corn oil, and fish oil, respectively. PhLOX showed good stability after storage at 4 °C for 2 weeks and broad tolerance to pH and temperature. These desirable properties of PhLOX make it a promising novel biocatalyst for the industrial production of volatile aroma compounds.
- Zhu, Zhu-Jun,Chen, Hai-Min,Chen, Juan-Juan,Yang, Rui,Yan, Xiao-Jun
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p. 1233 - 1241
(2018/02/19)
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- Structurally diverse glycoconjugated volatile compounds from Oxytropis falcata Bunge
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A phytochemical investigation on the whole plant of Oxytropis falcata Bunge yielded 16 glycoconjugated compounds with structurally diverse volatile aglycones but similar sugars. Of these, five were previously undescribed compounds with different volatile aglycones but same glucuronic acid (1 → 2) glucosyl moiety, including three octanol glucuronic acid (1 → 2) glucosides (1–3), one acyclic monoterpenoid glucuronic acid (1 → 2) glucoside (4), and one 4-phenyl-butan-2-ol glucuronic acid (1 → 2) glucoside (5), and 11 were biological related known glucoconjugated volatile compounds (6–16) isolated from genus Oxytropis for the first time. The structures of these compounds were determined by extensive spectroscopic analysis of MS, 1D and 2D NMR data. The absolute configurations of aglycones and sugar residues were assigned via enzymatic hydrolysis and subsequently comparison of the specific rotations. This is the first report of such structurally diverse glycoconjugated volatile compounds from O. falcata, which might be regarded as the precursor of free volatile compounds, and presents scientific evidences for better clarifying the volatile compositions of this medicinal plant and genus Oxytropis.
- Wang, Shanshan,Zhang, Xiaojing,Que, Sheng,Liang, Hong,Tu, Pengfei,Zhang, Qingying
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p. 143 - 147
(2018/07/29)
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- 1-Octen-3-ol Is Formed from Its Glycoside during Processing of Soybean [ Glycine max (L.) Merr.] Seeds
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Soaking and maceration of dry soybean seeds induce the formation of aliphatic volatile compounds that impact the flavor properties of food products prepared from soybean. Most aliphatic volatile compounds are formed through oxygenation of unsaturated fatty acids by lipoxygenases; however, lipoxygenases are not responsible for the formation of 1-octen-3-ol. 1-Octen-3-ol in soybean products is in general an off-flavor compound; thus, a procedure to manage its formation is required. In this study, we show that the formation of 1-octen-3-ol after hydration of soybean seed powder is independent of oxygen, suggesting that 1-octen-3-ol is not formed de novo from unsaturated fatty acids but instead from its derivative. When crude methanol extract of soybean seeds was reacted with β-glycosidases, 1-octen-3-ol was rather liberated from its glycoside. We purified the parent glycoside from soybean seeds and confirmed it as (R)-1-octen-3-yl β-primeveroside [(R)-1-octen-3-yl 6-O-β-d-xylopyranosyl-β-d-glucopyranoside]. Green immature soybean fruits (pericarp and seeds) contain a high amount of 1-octen-3-yl β-primeveroside. Its amount decreases after hydration of dry soybean powder. The results indicate that management of 1-octen-3-ol levels in soybean products requires a different strategy than that applied to off-flavor compounds formed de novo.
- Matsui, Kenji,Takemoto, Hiroyuki,Koeduka, Takao,Ohnishi, Toshiyuki
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p. 7409 - 7416
(2018/07/05)
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- Synthesis and pyrolysis of two flavor precursors of oct-1-en-3-yl methylpyrazinecarboxylates
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To rich flavor additive species of pyrazines, two new compounds of 3,6-dimethyl-2,5-pyrazinedicarboxylic acid 1-octen-3-yl ester (DMPOE) and 3,5,6-trimethyl-2-pyrazinecarboxylic acid 1-octen-3-yl ester (TMPOE) were synthesized by KMnO4 oxidatio
- Lai, Miao,Ji, Xiaoming,Tao, Tao,Shan, Yuanyuan,Liu, Pengfei,Zhao, Mingqin
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p. 1627 - 1638
(2017/05/19)
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- A general asymmetric synthesis of (R)-Matsutakeol and flavored analogs
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An efficient and practical synthetic route toward chiral matsutakeol and analogs was developed by asymmetric addition of terminal alkyne to aldehydes. (R)-matsutakeol and other flavored substances were feasibly synthesized from various alkylaldehydes in high yield (up to 49.5%, in three steps) and excellent enantiomeric excess (up to >99%). The protocols may serve as an alternative asymmetric synthetic method for active small-molecule library of natural fatty acid metabolites and analogs. These chiral allyl alcohols are prepared for food analysis and screening insect attractants.
- Liu, Jia,Li, Honglian,Zheng, Chao,Lu, Shichao,Guo, Xianru,Yin, Xinming,Na, Risong,Yu, Bin,Wang, Min
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- Fungal mediated kinetic resolution of racemic acetates to (R)-alcohols using Fusarium proliferatum
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Fungal mediated kinetic resolution of seven acyclic/aromatic acetates was achieved using Fusarium proliferatum to furnish (R)-alcohols in high enantiomeric excess (>95%). The kinetic resolution was established as one-pot two-step de-esterification/oxidation biocatalytic process. Further, the preparative scale synthesis of (R)-(+)-1-phenylethanol was accomplished through de-esterification/oxidation of (±)-1-phenylethyl acetate using the whole cell of F. proliferatum NCIM 1105.
- Jadhav, Dipesh D.,Patil, Harshal S.,Chaya, Patil S.,Thulasiram, Hirekodathakallu V.
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p. 4563 - 4567
(2016/09/23)
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- Regioselective Asymmetric Allylic Alkylation Reaction of α -Cyanoacetates Catalyzed by a Heterobimetallic Platina-/Palladacycle
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Allylic substitution reactions provide a valuable tool for the functionalization of CH acidic pronucleophiles. Often, control over the stereocenter generated at the nucleophilic reactant is still a challenge. The majority of studies that address this issue employ metal complexes with a low metal oxidation state (e.g. Pd0) to form allyl complexes through oxidative addition. In this article we describe the use of heterobimetallic PtII/PdII complexes, which probably activate the olefinic substrates through an SN2′ pathway. The reaction of α-cyanoacetates delivers linear allylation products with exclusive regioselectivity and high E/Z-selectivity for the new C=C double bond. Although the enantioselectivities attained are moderate, they are significantly higher than with related mono-PdII or -PtII catalysts or the corresponding bis-PdII complex, which indicates cooperation of the different metals. Control experiments suggest simultaneous activation of both reaction partners.
- Weiss, Marcel,Holz, Julia,Peters, Ren
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p. 210 - 227
(2016/01/20)
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- A 1-octene-3-ol synthesis method
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The invention discloses a synthesis method of 1-octylene-3-alcohol. The method comprises the following steps: (1) generating a Grignard reagent by virtue of reaction of bromopentane and maganesium; (2) generating 1-octylene-3-alcohol by virtue of reaction of the Grignard reagent and acrolein; and (3) carrying out after-treatment, namely stirring and hydrolyzing the 1-octylene-3-alcohol at the temperature of -2 to 3 DEG C, adjusting the pH value to be 1-5, carrying out vapor distillation, collecting distilled products at a boiling range of 60 to 65 DEG C under the pressure of 800Pa, and collecting the distilled products in different phases, thereby obtaining the 1-octylene-3-alcohol. The method is simple in process and high in yield, and waste water can be partially recycled.
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Paragraph 0030; 0031; 0032; 0033
(2017/01/12)
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- 1H-pyrrole-2,4-dicarbonyl-derivatives and their use as flavoring agents
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The present invention primarily relates to 1H-pyrrole-2,4-dicarbonyl-derivatives of Formula (I) wherein R1, R2, R3, Z. Z' and J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) or of a mixture of compounds of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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- Imidazo[1,2-a]pyridine-ylmethyl-derivatives and their use as flavoring agents
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The present invention primarily relates to imidazo[1,2-a]pyridine-ylmethyl-derivatives of Formula (I) wherein R1, R2, X, W e J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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- A stereoselective synthesis of the reported structure of polyporolide
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Polyporolide, isolated from a basidiomycete, was assigned a 4-hydroxy-5-(1-hydroxyhexyl)-dihydrofuran-2-one structure with anti-placement of the three contiguous stereocenters. A stereoselective total synthesis of the reported structure of the natural product involving two different routes is presented. A comparison of the spectral data of the synthesized molecule indicates the need for structure revision of natural polyporolide.
- Patil, Pradnya H.,Fernandes, Rodney A.
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p. 49189 - 49194
(2015/06/16)
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- Chemoenzymatic asymmetric total synthesis of nonanolide (Z)-cytospolides D, E and their stereoisomers
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Chemoenzymatic asymmetric total synthesis of the (Z)-isomer of the naturally occurring decanolide cytospolides D, E and six stereoisomers is reported. The main highlight of the synthetic venture involves ring-closing metathesis (RCM) reaction of a suitably functionalized ester compound, which was assembled by the Yamaguchi coupling of the required acid and alcohol fragments. The alcohol fragment was ac- cessed by two alternative chemoenzymatic processes, one being hydroxynitrile lyase mediated hydrocyanation, whereas lipase-catalyzed transesterification was the key sep in the second route. The acid fragment was constructed by an enantioselective enzymatic desymmetrization (EED) of prochiral 2-methyl-1,3-propanediol and Corey-Bakshi-Shibata (CBS) mediated stereoselective carbonyl reduction.
- Rej, Rohan Kalyan,Nanda, Samik
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p. 860 - 871
(2014/03/21)
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- Chemoenzymatic Asymmetric Total Synthesis of Nonanolide (Z)-Cytospolides D, e and Their Stereoisomers
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Chemoenzymatic asymmetric total synthesis of the (Z)-isomer of the naturally occurring decanolide cytospolides D, E and six stereoisomers is reported. The main highlight of the synthetic venture involves ring-closing metathesis (RCM) reaction of a suitably functionalized ester compound, which was assembled by the Yamaguchi coupling of the required acid and alcohol fragments. The alcohol fragment was accessed by two alternative chemoenzymatic processes, one being hydroxynitrile lyase mediated hydrocyanation, whereas lipase-catalyzed transesterification was the key sep in the second route. The acid fragment was constructed by an enantioselective enzymatic desymmetrization (EED) of prochiral 2-methyl-1,3-propanediol and Corey-Bakshi-Shibata (CBS) mediated stereoselective carbonyl reduction.
- Rej, Rohan Kalyan,Nanda, Samik
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p. 860 - 871
(2015/10/05)
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- Arachidonic acid-dependent carbon-eight volatile synthesis from wounded liverwort (Marchantia polymorpha)
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Eight-carbon (C8) volatiles, such as 1-octen-3-ol, octan-3-one, and octan-3-ol, are ubiquitously found among fungi and bryophytes. In this study, it was found that the thalli of the common liverwort Marchantia polymorpha, a model plant species, emitted high amounts of C8 volatiles mainly consisting of (R)-1-octen-3-ol and octan-3-one upon mechanical wounding. The induction of emission took place within 40 min. In intact thalli, 1-octen-3-yl acetate was the predominant C8 volatile while tissue disruption resulted in conversion of the acetate to 1-octen-3-ol. This conversion was carried out by an esterase showing stereospecificity to (R)-1-octen-3-yl acetate. From the transgenic line of M. polymorpha (des6KO) lacking arachidonic acid and eicosapentaenoic acid, formation of C8 volatiles was only minimally observed, which indicated that arachidonic and/or eicosapentaenoic acids were essential to form C8 volatiles in M. polymorpha. When des6KO thalli were exposed to the vapor of 1-octen-3-ol, they absorbed the alcohol and converted it into 1-octen-3-yl acetate and octan-3-one. Therefore, this implied that 1-octen-3-ol was the primary C8 product formed from arachidonic acid, and further metabolism involving acetylation and oxidoreduction occurred to diversify the C8 products. Octan-3-one was only minimally formed from completely disrupted thalli, while it was formed as the most abundant product in partially disrupted thalli. Therefore, it is assumed that the remaining intact tissues were involved in the conversion of 1-octen-3-ol to octan-3-one in the partially disrupted thalli. The conversion was partly promoted by addition of NAD(P)H into the completely disrupted tissues, suggesting an NAD(P)H-dependent oxidoreductase was involved in the conversion.
- Kihara, Hirotomo,Tanaka, Maya,Yamato, Katsuyuki T.,Horibata, Akira,Yamada, Atsushi,Kita, Sayaka,Ishizaki, Kimitsune,Kajikawa, Masataka,Fukuzawa, Hideya,Kohchi, Takayuki,Akakabe, Yoshihiko,Matsui, Kenji
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supporting information
p. 42 - 49
(2015/02/19)
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- Stereochemistry and mechanism of enzymatic and non-enzymatic hydrolysis of benzylic sec-sulfate esters
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The substrate scope of inverting alkylsulfatase Pisa1 was extended towards benzylic sec-sulfate esters by suppression of competing non-enzymatic autohydrolysis by addition of dimethyl sulfoxide as co-solvent. Detailed investigation of the mechanism of autohydrolysis in 18O-labeled buffer by using an enantiopure sec-benzylic sulfate ester as substrate revealed that from the three possible pathways (i) inverting SN2-type nucleophilic attack of [OH-] at the benzylic carbon represents the major pathway, whereas (ii) SN1-type formation of a planar benzylic carbenium ion leading to racemization was a minor event, and (iii) Retaining SN2-type nucleophilic attack at sulfur took place at the limits of detection. The data obtained are interpreted by analysis of Hammett constants of meta substituents. The enzymatic hydrolysis of benzylic sec-sulfate esters by alkylsulfatase Pisa1 proceeded with clean inversion of configuration and with excellent stereoselectivities when the competing non-enzymatic hydrolysis was suppressed by addition of dimethyl sulfoxide as co-solvent. Copyright
- Toesch, Michael,Schober, Markus,Breinbauer, Rolf,Faber, Kurt
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p. 3930 - 3934
(2014/06/24)
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- Bis(imino)pyridine cobalt-catalyzed dehydrogenative silylation of alkenes: Scope, mechanism, and origins of selective allylsilane formation
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The aryl-substituted bis(imino)pyridine cobalt methyl complex, ( MesPDI)CoCH3 (MesPDI = 2,6-(2,4,6-Me 3C6H2-N=CMe)2C5H 3N), promotes the catalytic dehydrogenative silylation of linear α-olefins to selectively form the corresponding allylsilanes with commercially relevant tertiary silanes such as (Me3SiO) 2MeSiH and (EtO)3SiH. Dehydrogenative silylation of internal olefins such as cis- and trans-4-octene also exclusively produces the allylsilane with the silicon located at the terminus of the hydrocarbon chain, resulting in a highly selective base-metal-catalyzed method for the remote functionalization of C-H bonds with retention of unsaturation. The cobalt-catalyzed reactions also enable inexpensive α-olefins to serve as functional equivalents of the more valuable α, ω-dienes and offer a unique method for the cross-linking of silicone fluids with well-defined carbon spacers. Stoichiometric experiments and deuterium labeling studies support activation of the cobalt alkyl precursor to form a putative cobalt silyl, which undergoes 2,1-insertion of the alkene followed by selective β-hydrogen elimination from the carbon distal from the large tertiary silyl group and accounts for the observed selectivity for allylsilane formation.
- Atienza, Crisita Carmen Hojilla,Diao, Tianning,Weller, Keith J.,Nye, Susan A.,Lewis, Kenrick M.,Delis, Johannes G. P.,Boyer, Julie L.,Roy, Aroop K.,Chirik, Paul J.
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supporting information
p. 12108 - 12118
(2014/10/16)
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- Homogeneous Pd-catalyzed transformation of terminal alkenes into primary allylic alcohols and derivatives
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Synthesis of primary alcohols from terminal alkenes is an important process in both bulk and fine chemical syntheses. Herein, a homogeneous Pd-complex-catalyzed transformation of terminal alkenes into primary allylic alcohols, by using 5 mol % [Pd(PPh3)4] as a catalyst, and H2O, CO2, and quinone derivatives as reagents, is reported. When alcohols were used instead of H2O, allylic ethers were obtained. A proposed mechanism includes the addition of oxygen nucleophiles at the less-hindered terminal position of π-allyl Pd intermediates.
- Tomita, Ren,Mantani, Kohei,Hamasaki, Akiyuki,Ishida, Tamao,Tokunaga, Makoto
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supporting information
p. 9914 - 9917
(2014/08/18)
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- NHC-copper hydrides as chemoselective reducing agents: Catalytic reduction of alkynes, alkyl triflates, and alkyl halides
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The NHC-copper-catalyzed Z-selective semi-reduction of terminal and internal alkynes, as well as the NHC-copper-catalyzed reduction of primary alkyl triflates and primary and secondary alkyl iodides and bromides are described. The high chemoselectivity demonstrated in these examples illustrates the mild nature of copper hydride complexes as reducing agents, which have applications in synthetic chemistry beyond their traditional role in the reduction of activated alkenes and carbonyl compounds.
- Cox, Nick,Dang, Hester,Whittaker, Aaron M.,Lalic, Gojko
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supporting information
p. 4219 - 4231
(2014/06/09)
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- A palladium nanoparticle-nanomicelle combination for the stereo-selective semihydrogenation of alkynes in water at room temperature
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The addition of NaBH4 to Pd(OAc) 2 in water containing nanomicelles leads to the generation of H2 and Pd nanoparticles. Subsequent reduction of disubstituted alkynes affords Z-alkenes in high yields. These reactions are general, take place in water at ambient temperatures, and offer recycling of the aqueous reaction mixture along with low overall E Factors.
- Slack, Eric D.,Gabriel, Christopher M.,Lipshutz, Bruce H.
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supporting information
p. 14051 - 14054
(2015/02/19)
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- Clinprost, Isocarbacyclin And Analogs Thereof And Methods Of Making The Same
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In one aspect, methods of synthesizing clinprost, isocarbacyclin and analogs thereof are described herein which, in some embodiments, permit an abbreviated synthetic pathway in comparison to one or more prior synthetic methods. By providing a compact synthetic scheme, methods described herein can reduce cost, waste and time of clinprost and isocarbacyclin synthesis while facilitating the development and investigation of analogs of these compounds.
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- Chiral Co(II) metal-organic framework in the heterogeneous catalytic oxidation of alkenes under aerobic and anaerobic conditions
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The chiral Co(II) MOF [Co(l-RR)(H2O)·H2O] ∞ [1; l-RR = (R,R)-thiazolidine-2,4-dicarboxylate] has been exploited in the catalytic oxidation of different alkenes (cyclohexene, (Z)-cyclooctene, 1-octene) using either tert-butyl hydroperoxide ( tBuOOH) or molecular oxygen (O2) as oxidants. Different chemoselectivities are observed, both substrate- and oxidant-dependent. A moderate enantioselectivity is also obtained in the case of prochiral precursors, revealing the chiral induction ability of the optically pure metal environment. The interaction of O2 with the exposed metal sites in 1 (after material preactivation and consequent removal of the coordinated aquo ligand) has been studied through TPD-MS analysis combined with DFT calculations, with the aim of probing effective oxygen uptake by the heterogeneous catalyst and unraveling the nature of the active species in the catalytic oxidation process under aerobic conditions. Theoretical results indicate the presence of an η1-superoxo species at the cobalt center, with concomitant Co(II) ? Co(III) oxidation. Finally, the experimental estimation of the O2 adsorption enthalpy is found to be in good agreement with the calculated binding energy.
- Tuci, Giulia,Giambastiani, Giuliano,Kwon, Stephanie,Stair, Peter C.,Snurr, Randall Q.,Rossin, Andrea
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p. 1032 - 1039
(2014/04/03)
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- Stereoselective synthesis of functionalized cyclic amino acid derivatives via a [2,3]-stevens rearrangement and ring-closing metathesis
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Unnatural cyclic amino acids are valuable tools in biomedical research and drug discovery. A two-step stereoselective strategy for converting simple glycine-derived aminoesters into unnatural cyclic amino acid derivatives has been developed. The process includes a palladium-catalyzed tandem allylic amination/[2,3]-Stevens rearrangement followed by a ruthenium-catalyzed ring-closing metathesis. The [2,3]-rearrangement proceeds with high diastereoselectivity through an exo transition state. Oppolzer's chiral auxiliary was utilized to access an enantiopure cyclic amino acid by this approach, which will enable future biological applications.
- Nash, Aaron,Soheili, Arash,Tambar, Uttam K.
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supporting information
p. 4770 - 4773
(2013/10/08)
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- Monophasic catalytic system for the selective semireduction of alkynes
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A highly efficient semireduction of alkynes has been developed. Using 0.5-2 mol % of a copper catalyst, semireduction can be accomplished with a wide range of substrates, including both internal and terminal alkynes without over-reduction. The new method has excellent chemoselectivity, and the semireduction can be accomplished even in the presence of nitro and aryl iodo groups. Finally, commercial availability of a catalyst precursor adds to the appeal of the new catalytic system.
- Whittaker, Aaron M,Lalic, Gojko
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supporting information
p. 1112 - 1115
(2013/04/10)
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- Sequential Pd(0)-, Rh(I)-, and Ru(II)-catalyzed reactions in a nine-step synthesis of clinprost
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A step-economical synthesis of clinprost is reported that concludes with 3 different transition metal-catalyzed reactions: Pd-catalyzed decarboxylation with allylic rearrangement, Rh-catalyzed diene-ene [2+2+1] reaction, and Ru-catalyzed cross-metathesis reaction. The complexity bestowed to the molecule from these reactions converts a readily accessible ester to clinprost without using protecting groups in only 9 total steps.
- Nagy, Emma E.,Hyatt, I. F. Dempsey,Gettys, Kristen E.,Yeazell, Shawn T.,Frempong Jr., Stephen K.,Croatt, Mitchell P.
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supporting information
p. 586 - 589
(2013/03/29)
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- Modular enantioselective synthesis of 8-aza-prostaglandin E1
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We report herein for the first time the enantioselective synthesis of 8-aza-PGE1. The synthesis used the cross olefin metathesis reaction to connect the 5-vinyl-γ-lactam subunit, prepared from (R)-malic acid via the Ley's sulfone-based α-amidalkylation protocol (dr = 6.8:1), with the chiral pre-ω-chain. The latter was synthesized in high enantioselectivity from (E)-2-octenol by the Sharpless asymmetric epoxidation and the titanocene-mediated epoxide opening. This modular approach is quite concise and flexible, and requires only eight steps from commercially available reagents.
- Wang, Xiao-Gang,Wang, Ai-E,Hao, Yi,Ruan, Yuan-Ping,Huang, Pei-Qiang
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p. 9488 - 9493
(2013/10/08)
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- Simple and efficient 1,3-isomerization of allylic alcohols using a supported monomeric vanadium-oxide catalyst
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Promotion by group high five: Silica-supported monomeric vanadium-oxide promoted the isomerization of various allylic alcohols, including under scaled-up and solvent-free reaction conditions. This catalyst also exhibited high reusability with no drop in activity.
- Mitsudome, Takato,Sueoka, Shoichiro,Ikeda, Satoshi,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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p. 2879 - 2882
(2013/10/21)
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- Scopariusic acid, a new meroditerpenoid with a unique cyclobutane ring isolated from Isodon scoparius
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Scopariusic acid (1), a new ent-clerodane-based meroditerpenoid with a unique cyclobutane ring and an unusual 1-octen-3-ol substituent, together with its biosynthetic related compound 2, were isolated from the aerial parts of Isodon scoparius. The structures of 1 and 2, including their absolute configurations, were determined by spectroscopic methods, single-crystal X-ray diffraction analysis, and chemical methods. Compound 1 showed weak cytotoxicity and moderate immunosuppressive activity.
- Zhou, Min,Zhang, Hai-Bo,Wang, Wei-Guang,Gong, Ning-Bo,Zhan, Rui,Li, Xiao-Nian,Du, Xue,Li, Li-Mei,Li, Yan,Lu, Yang,Pu, Jian-Xin,Sun, Han-Dong
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supporting information
p. 4446 - 4449
(2013/09/24)
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- Selective syntheses of Δα,β and Δβ,γ butenolides from allylic cyclopropenecarboxylates via tandem ring expansion/[3,3]-sigmatropic rearrangements
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Allylic cyclopropenecarboxylates undergo ring expansion reactions to give 2-allyloxyfuran intermediates, which subsequently rearrange to Δβ,γ butenolides via a Claisen rearrangement or to the corresponding Δα,β butenolides via further Cope rearrangement. Also described are methods for chirality transfer in the rearrangement of nonracemic allylic esters.
- Xie, Xiaocong,Li, Yi,Fox, Joseph M.
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supporting information
p. 1500 - 1503
(2013/07/05)
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- The substrate spectrum of the inverting sec-alkylsulfatase Pisa1
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The substrate spectrum of the inverting alkylsulfatase Pisa1 was investigated using a range of sec-alkyl sulfate esters bearing aromatic, olefinic and acetylenic moieties. Perfect enantioselectivities were obtained for substrates bearing groups of different size adjacent to the sulfate ester moiety. Insufficient selectivities could be doubled by using dimethyl sulfoxide (DMSO) as co-solvent. Hydrolytically unstable benzylic sulfate esters could be sufficiently stabilised by introduction of electron-withdrawing substituents. Overall, Pisa1 appears to be a very useful inverting alkylsulfatase for the deracemisation of rac-sec-alcohols via enzymatic hydrolysis of their corresponding sulfate esters, which furnishes homochiral products possessing the 'anti-Kazlauskas' configuration. Copyright
- Schober, Markus,Knaus, Tanja,Toesch, Michael,MacHeroux, Peter,Wagner, Ulrike,Faber, Kurt
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p. 1737 - 1742
(2012/07/31)
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- The effect of encapsulated Zn-POM on the catalytic activity of MIL-101 in the oxidation of alkenes with hydrogen peroxide
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Zinc monosubstituted Keggin heteropolyanion [PZnMo2W 9O39]5- was electrostatically bound to nanocages of MIL-101 polymer matrix. The Zn-POM@MIL-101 catalyst was characterized by XRD, N2 adsorption, atomic absorption (AAS), and FT-IR spectroscopic methods. The catalytic activity of the new composite material, Zn-POM@MIL-101, was assessed in the oxidation of alkenes using aqueous hydrogen peroxide as oxidant. Zn-POM@MIL-101/H2O2 catalytic system demonstrated good catalytic activity in the oxidation reactions. Zn-POM@MIL-101 was reusable for three catalytic cycles. While the MIL-101 matrix is an active catalyst in these oxidation reactions, the presence of Zn-POM significantly changed the selectivity and reaction times. Copyright
- Saedi, Zahra,Tangestaninejad, Shaharm,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj
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experimental part
p. 463 - 473
(2012/05/20)
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- The first stereoselective total synthesis of the Z-isomer of cytospolide e
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A convergent and highly stereoselective total synthesis of the Z-isomer of cytospolide E has been achieved via Evan's aldol reaction, Sharpless kinetic resolution and RCM cyclisation.
- Yadav,Pandurangam,Suman Kumar,Adi Narayana Reddy,Prasad,Reddy, B.V. Subba,Rajendraprasad,Kunwar
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p. 6048 - 6050
(2012/11/07)
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- Syntheses of enantiopure aliphatic secondary alcohols and acetates by bioresolution with lipase B from candida antarctica
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The lipase B from Candida antarctica (Novozym 435, CALB) efficiently catalyzed the kinetic resolution of some aliphatic secondary alcohols: (±)-4-methylpentan- 2-ol (1), (±)-5-methylhexan-2-ol (3), (±)-octan-2-ol (4), (±)-heptan-3-ol (5) and (±)-oct-1- en-3-ol (6). The lipase showed excellent enantioselectivities in the transesterifications of racemic aliphatic secondary alcohols producing the enantiopure alcohols (>99% ee) and acetates (>99% ee) with good yields. Kinetic resolution of rac-alcohols was successfully achieved with CALB lipase using simple conditions, vinyl acetate as acylating agent, and hexane as non-polar solvent.
- Ferreira, Hercules V.,Rocha, Lenilson C.,Severino, Richele P.,Porto, Andre L. M.
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p. 8955 - 8967,13
(2020/08/31)
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- A convenient access to γ-lactones from O-allyl-α-bromoesters using a one-pot ionic-radical-ionic sequence
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Cognac in the jar! An efficient one-pot sequence for the preparation of γ-lactones is described. Following reduction of α-bromo ester precursors with DIBAL-H and radical cyclization of the resulting O-aluminum acetals, a preparative in-situ Oppenauer-type oxidation of the cyclic O-aluminum acetal using simple aldehydes or ketones gives access to γ-lactones in high yields. Copyright
- Beneteau, Romain,Lebreton, Jacques,Denes, Fabrice
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supporting information; experimental part
p. 1516 - 1520
(2012/09/08)
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- L-Proline-derived ligands to mimic the '2-His-1-carboxylate' triad of the non-haem iron oxidase active site
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Non-haem iron(II) oxidases (NHIOs) catalyse a variety of oxidative transformations in biology. The iron-binding environment of the NHIO active site typically incorporates a '2-His-1-carboxylate' facial triad of amino acid side-chains, a motif that has emerged as a defining feature of the enzyme family. Towards the goal of biomimetic, iron-mediated C-H activation we have synthesized a series of peptidomimetic ligands from l-proline. By coupling l-proline to 2,6-bis(bromomethyl)pyridine, 2-(bromomethyl)-6-((tert- butyldimethylsilyloxy)methyl)pyridine and picolinic acid, we have generated several new ligand architectures designed to complex with iron(II) and mimic the NHIO active site. The resulting iron complexes promote modest levels of alkene dihydroxylation and allylic oxidation using hydrogen peroxide as oxidant.
- Dungan, Victoria J.,Wong, Shwo Mun,Barry, Sarah M.,Rutledge, Peter J.
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experimental part
p. 3231 - 3236
(2012/06/01)
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