- Heterogeneous Hydroxyl-Directed Hydrogenation: Control of Diastereoselectivity through Bimetallic Surface Composition
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Directed hydrogenation, in which product selectivity is dictated by the binding of an ancillary directing group on the substrate to the catalyst, is typically catalyzed by homogeneous Rh and Ir complexes. No heterogeneous catalyst has been able to achieve equivalently high directivity due to a lack of control over substrate binding orientation at the catalyst surface. In this work, we demonstrate that Pd-Cu bimetallic nanoparticles with both Pd and Cu atoms distributed across the surface are capable of high conversion and diastereoselectivity in the hydroxyl-directed hydrogenation reaction of terpinen-4-ol. We postulate that the OH directing group adsorbs to the more oxophilic Cu atom while the olefin and hydrogen bind to adjacent Pd atoms, thus enabling selective delivery of hydrogen to the olefin from the same face as the directing group with a 16:1 diastereomeric ratio.
- Shumski, Alexander J.,Swann, William A.,Escorcia, Nicole J.,Li, Christina W.
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p. 6128 - 6134
(2021/05/29)
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- From Bugs to Bioplastics: Total (+)-Dihydrocarvide Biosynthesis by Engineered Escherichia coli
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The monoterpenoid lactone derivative (+)-dihydrocarvide ((+)-DHCD) can be polymerised to form shape-memory polymers. Synthetic biology routes from simple, inexpensive carbon sources are an attractive, alternative route over chemical synthesis from (R)-carvone. We have demonstrated a proof-of-principle in vivo approach for the complete biosynthesis of (+)-DHCD from glucose in Escherichia coli (6.6 mg L?1). The pathway is based on the Mentha spicata route to (R)-carvone, with the addition of an ′ene′-reductase and Baeyer–Villiger cyclohexanone monooxygenase. Co-expression with a limonene synthesis pathway enzyme enables complete biocatalytic production within one microbial chassis. (+)-DHCD was successfully produced by screening multiple homologues of the pathway genes, combined with expression optimisation by selective promoter and/or ribosomal binding-site screening. This study demonstrates the potential application of synthetic biology approaches in the development of truly sustainable and renewable bioplastic monomers.
- Ascue Avalos, Gabriel A.,Toogood, Helen S.,Tait, Shirley,Messiha, Hanan L.,Scrutton, Nigel S.
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p. 785 - 792
(2019/01/29)
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- Dihydridoboranes: Selective Reagents for Hydroboration and Hydrodefluorination
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The preparation of a new series of dihydridoboranes supported by N,N-chelating ligands, [R2NCH2CH2NAr]- (R = alkyl, Ar = aryl), is reported. These new boranes react selectively with carbonyls, imines, and a series of electron-deficient fluoroarenes. The reactivity is complementary to recognized reagents such as pinacolborane, catecholborane, NHC-BH3, and borane (BH3) itself. Selectivities are rationalized by invoking both open- A nd closed-chain forms of the reagents as part of equilibrium mixtures.
- Phillips, Nicholas A.,O'hanlon, James,Hooper, Thomas N.,White, Andrew J. P.,Crimmin, Mark R.
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supporting information
p. 7289 - 7293
(2019/10/08)
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- Stereodivergent Synthesis of Carveol and Dihydrocarveol through Ketoreductases/Ene-Reductases Catalyzed Asymmetric Reduction
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Chiral carveol and dihydrocarveol are important additives in the flavor industry and building blocks in the synthesis of natural products. Despite the remarkable progress in asymmetric catalysis, convenient access to all possible stereoisomers of carveol and dihydrocarveol remains a challenge. Here, we present the stereodivergent synthesis of carveol and dihydrocarveol through ketoreductases/ene-reductases catalyzed asymmetric reduction. By directly asymmetric reduction of (R)- and (S)-carvone using ketoreductases, which have Prelog or anti-Prelog stereopreference, all four possible stereoisomers of carveol with medium to high diastereomeric excesses (up to >99 %) were first observed. Then four stereoisomers of dihydrocarvone were prepared through ene-reductases catalyzed diastereoselective synthesis. Asymmetric reduction of obtained dihydrocarvone isomers by ketoreductases further provide access to all eight stereoisomeric dihydrocarveol with up to 95 % de values. In addition, the absolute configurations of dihydrocarveol stereoisomers were determined by using modified Mosher's method.
- Guo, Jiyang,Zhang, Rui,Ouyang, Jingping,Zhang, Feiting,Qin, Fengyu,Liu, Guigao,Zhang, Wenhe,Li, Hengyu,Ji, Xiaohong,Jia, Xian,Qin, Bin,You, Song
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p. 5496 - 5504
(2018/11/30)
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- Production of flavours and fragrances via bioreduction of (4R)-(-)-carvone and (1R)-(-)-myrtenal by non-conventional yeast whole-cells
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As part of a program aiming at the selection of yeast strains which might be of interest as sources of natural flavours and fragrances, the bioreduction of (4R)-(-)-carvone and (1R)-(-)-myrtenal by whole-cells of non-conventional yeasts (NCYs) belonging to the genera Candida, Cryptococcus, Debaryomyces, Hanseniaspora, Kazachstania, Kluyveromyces, Lindnera, Nakaseomyces, Vanderwaltozyma and Wickerhamomyces was studied. Volatiles produced were sampled by means of headspace solid-phase microextraction (SPME) and the compounds were analysed and identified by gas chromatography-mass spectroscopy (GC-MS). Yields (expressed as % of biotransformation) varied in dependence of the strain. The reduction of both (4R)-(-)-carvone and (1R)-(-)-myrtenal were catalyzed by some ene-reductases (ERs) and/or carbonyl reductases (CRs), which determined the formation of (1R,4R)-dihydrocarvone and (1R)-myrtenol respectively, as main flavouring products. The potential of NCYs as novel whole-cell biocatalysts for selective biotransformation of electron-poor alkenes for producing flavours and fragrances of industrial interest is discussed.
- Goretti, Marta,Turchetti, Benedetta,Cramarossa, Maria Rita,Forti, Luca,Buzzini, Pietro
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p. 5736 - 5748
(2013/07/19)
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- Synthesis of optically active dihydrocarveol via a stepwise or one-pot enzymatic reduction of (R)- and (S)-carvone
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A recombinant enoate reductase LacER from Lactobacillus casei catalyzed the reduction of (R)-carvone and (S)-carvone to give (2R,5R)-dihydrocarvone and (2R,5S)-dihydrocarvone with 99% and 86% de, respectively, which were further reduced to dihydrocarveols by a carbonyl reductase from Sporobolomyces salmonicolor SSCR or Candida magnolia CMCR. For (R)-carvone, (1S,2R,5R)-dihydrocarveol was produced as the sole product with >99% conversion, while (1S,2R,5S)-dihydrocarveol was obtained as the major product, but with a lower de when (S)-carvone was used as the substrate. The one-pot reduction was performed at a 0.1 M substrate concentration, indicating that it might provide an effective synthetic route to this type of chiral compound.
- Chen, Xi,Gao, Xiuzhen,Wu, Qiaqing,Zhu, Dunming
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experimental part
p. 734 - 738
(2012/08/29)
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- Synthesis of a key intermediate for the total synthesis of pseudopteroxazole
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A facile synthesis of a key intermediate for the total synthesis of anti-mycobacterial compound pseudopteroxazole is described employing an intramolecular Diels-Alder cyclization and an iodine-mediated oxidative aromatization step.
- Yadav,Bhasker, E. Vijaya,Srihari
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experimental part
p. 1997 - 2004
(2010/04/29)
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- Total synthesis of (-)-colombiasin A and (-)-elisapterosin B
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Intramolecular cycloaddition reactions are central in the total syntheses of colombiasin A (1) and elisapterosin B (2) described, which use (-)-dihydrocarvone as the starting material. A Moore rearrangement of a vinylcyclobutene is used to initiate the cycloaddition.
- Harrowven, David C.,Pascoe, David D.,Demurtas, Daniela,Bourne, Heather O.
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p. 1221 - 1222
(2007/10/03)
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- Organic reactions in a solid matrix-VII sodium on alumina: A convenient reagent for reduction of ketones, esters and oximes
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Sodium dispersed on alumina is described and evaluated as a convenient off-the-shelf reagent (in a wax-coated form) for reduction of ketones, esters and oximes. While isopropanol is the preferred proton donor for the reduction of ketones and oximes, t-butanol is the alcohol of choice for the reduction of esters.
- Singh, Satendra,Dev, Sukh
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p. 10959 - 10964
(2007/10/02)
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- 25-Hydroxydihydrotachysterol2. An innovative synthesis of a key metabolite of dihydrotachysterol2
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A new synthesis of 25-hydroxydihydrotachysterol2 is described. The hydroxylated side-chain is constructed stereoselectively using a chiral Wittig reagent. The A-ring synthon is introduced utilising the Wittig-Horner method as developed by Lythgoe et al. The preparation of the metabolite is carried out in 18 steps.
- Hanekamp,Rookhuizen,Bos,Brandsma
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p. 9283 - 9294
(2007/10/02)
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- Stereoselective reduction of (R)-(-)-carvone with sodium dithionite in the presence of cyclomaltoheptaose (β-cyclodextrin) and its heptakis(2,6-di-O-methyl) derivative
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The authors have studied the competition between l,4 and l,2-reduction of the conjugated enone (r)-(-)-carvone in the presence of cyclomaltoheptaose and its heptakis derivative using sodium dithionite as a reducing agent in aqueous sodium hydrogen carbonate with or without benzene. The spectrum of products namely the ketones and the alcohols expected from the non-selective reduction of an organic compound is shown.
- Fornasier,Marcuzzi,Parmagnani,Tonellato
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p. 245 - 249
(2007/10/02)
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- Enantioselectivity in the Biotransformation of Mono- and Bicyclic Monoterpenoids with the Cultured Cells of Nicotiana tabacum
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The biotransformation of the enantiomeric pairs of p-menthane and bicyclo and heptane derivatives with the cultured cells of Nicotiana tabacum was investigated.It was found that (i) the cultured cells discriminate the enantiomers of p-menthan-2-ol and bicycloheptan-2-ol and bicycloheptan-3-ol derivatives, and enantioselectively convert these alcohols to the corresponding ketones, (ii) the cells reduce the carbonyl group of p-methan-2-one derivatives to a high extent, but not that of p-menthan-3-ones, and (iii) the cells discriminate the enantiomers of bicyclohept-2-en-4-one (verbenone) and enantioselectively reduce the C-C double bond of the (1S,5S)-enantiomer.
- Hamada, Hiroki
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p. 869 - 878
(2007/10/02)
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- FUNCTIONALIZED CYCLOPENTANES VIA RADICAL CYCLIZATIONS USING THIOCARBONATE DERIVATIVES AS INITIATORS AND TERMINATORS
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A radical-based cyclization is described that employs xanthates or cyclic thionocarbonates as initiators and allylic dithiocarbonates or allylic thiocarbamates as terminators.
- Ziegler, Frederick E.,Zheng, Zhong-li
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p. 5973 - 5976
(2007/10/02)
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- Stereospecific synthesis of (+) 2R, 5R trans dihydrocarvone from (-) carvone
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(+) 2R, 5R trans dihydrocarvone was prepared stereospecifically in a large scale experiment by stereospecific addition of thiophenol to the conjugated double bond of (-) carvone, followed by desulfurization.
- Solladie, Guy,Hutt, Jean
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p. 643 - 644
(2007/10/02)
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- THE BIOTRANSFORMATION OF CARVOXIME AND DEHYDROCARVOXIME WITH CELL SUSPENSION CULTURES OF NICOTIANA TABACUM
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In newly initiated cell suspension cultures of Nicotiana tabacum (4R)-(-)-and (4S)-(+)-carvoximes and (1S,4R)-(+)-dihydrocarvoxime were hydrolysed to the corresponding ketones and then the resultant ketones were reduced to the corresponding alcohols.Key words: Nicotiana tabacum; Solanaceae; tissue culture; biotransformation; hydrolysis; carvoxime; dihydrocavoxime.
- Suga, Takayuki,Hirata, Toshifumi,Futatsugi, Masayuki
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p. 1327 - 1328
(2007/10/02)
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- REACTIONS OF p-TOLUENESULFONIC ACID TERPENE DERIVATIVES WITH LITHIUM IN ETHYLAMINE
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Reactions of terpene p-toluenesulfonamides and p-toluenesulfonates with lithium in ethylamine were stated to afford, exclusively or mainly, respective amines and alcohols as the result of N-S or O-S bond cleavage.Presence of hydroxyl groups is not a hindrance. 2α-Hydroxy-3α-tosyloxypinane undergoes, partially, a rearrangement.The mechanism of that reaction is discussed.
- Rykowski, Zbigniew,Gubrynowicz, Olaf,Wrzesien, Justyna
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p. 1237 - 1244
(2007/10/02)
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- STEREOSELECTIVITY OF THE REDUCTION OF CARVONE AND DIHYDROCARVONE BY SUSPENSION CELLS OF NICOTIANA TABACUM
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The biotransformation of foreign substrates with suspension cells of Nicotiana tabacum was tested with (4R)-(-)- and (4S)-(+)-carvones, (1R,4R)-(+)- and (1S,4S)-(-)-dihydrocarvones and (1S,4R)-(+)- and (1R,4S)-(-)-isodihydrocarvones.It was found that the cells reduced regio- and stereoselectively the C-C double bond adjacent to the carbonyl group from the si-face and then the carbonyl group from the re-face, leaving the C-C double bond in the 1-methylethenyl group unattacked. - Key Word Index - Nicotiana tabacum; Solanaceae; tissue culture; biotransformation; stereoselective reduction; carvone; dihydrocarvone; isodihydrocarvone.
- Hirata, Toshifumi,Hamada, Hiroki,Aoki, Tadashi,Suga, Takayuki
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p. 2209 - 2212
(2007/10/02)
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