- Enzymatic production of both enantiomers of rhododendrol
-
An asymmetric synthetic approach to produce (R)- and (S)-rhododendrol is described. W110A Thermoanaerobacter ethanolicus secondary alcohol dehydrogenase (W110A Te SADH), an (S)-specific mutant of TeSADH, is used in this approach. The enantioselective redu
- Musa, Musa M.
-
-
Read Online
- Deracemization and Stereoinversion of Alcohols Using Two Mutants of Secondary Alcohol Dehydrogenase from Thermoanaerobacter pseudoethanolicus
-
We developed a one-pot sequential two-step deracemization approach to chiral alcohols using two mutants of Thermoanaerobacter pseudoethanolicus secondary alcohol dehydrogenase (TeSADH). This approach relies on consecutive non-stereospecific oxidation of alcohols and stereoselective reduction of their prochiral ketones using two mutants of TeSADH with poor and good stereoselectivities, respectively. More specifically, W110G TeSADH enables a non-stereospecific oxidation of alcohol racemates to their corresponding prochiral ketones, followed by W110V TeSADH-catalyzed stereoselective reduction of the resultant ketone intermediates to enantiopure (S)-configured alcohols in up to > 99 percent enantiomeric excess. A heat treatment after the oxidation step was required to avoid the interference of the marginally stereoselective W110G TeSADH in the reduction step; this heat treatment was eliminated by using sol-gel encapsulated W110G TeSADH in the oxidation step. Moreover, this bi-enzymatic approach was implemented in the stereoinversion of (R)-configured alcohols, and (S)-configured alcohols with up to > 99 percent enantiomeric excess were obtained by this Mitsunobu-like stereoinversion reaction.
- Hamdan, Samir M.,Musa, Musa M.,Nafiu, Sodiq A.,Takahashi, Etsuko,Takahashi, Masateru
-
supporting information
(2020/07/24)
-
- Expanding the Substrate Specificity of Thermoanaerobacter pseudoethanolicus Secondary Alcohol Dehydrogenase by a Dual Site Mutation
-
Here, we report the asymmetric reduction of selected phenyl-ring-containing ketones by various single- and dual-site mutants of Thermoanaerobacter pseudoethanolicus secondary alcohol dehydrogenase (TeSADH). The further expansion of the size of the substrate binding pocket in the mutant W110A/I86A not only allowed the accommodation of substrates of the single mutants W110A and I86A within the expanded active site but also expanded the substrate range of the enzyme to ketones bearing two sterically demanding groups (bulky–bulky ketones), which are not substrates for the TeSADH single mutants. We also report the regio- and enantioselective reduction of diketones with W110A/I86A TeSADH and single TeSADH mutants. The double mutant exhibited dual stereopreference to generate the Prelog products most of the time and the anti-Prelog products in a few cases.
- Musa, Musa M.,Bsharat, Odey,Karume, Ibrahim,Vieille, Claire,Takahashi, Masateru,Hamdan, Samir M.
-
p. 798 - 805
(2018/02/21)
-
- Selective hydrogenation of conjugated unsaturated ketones containing a hydroxyaryl substituent in the β-position
-
A high selectivity was achieved in the Ni2B-catalyzed hydrogenation of α,β-unsaturated ketones containing a hydroxyaryl (phenolic) substituent in the β-position. The developed hydrogenation procedure was used to synthesize natural compounds of the phenylpropane series and their structural analogs.
- Kovalenko,Pratsko
-
-
- Deracemization of Secondary Alcohols by using a Single Alcohol Dehydrogenase
-
We developed a single-enzyme-mediated two-step approach for deracemization of secondary alcohols. A single mutant of Thermoanaerobacter ethanolicus secondary alcohol dehydrogenase enables the nonstereoselective oxidation of racemic alcohols to ketones, followed by a stereoselective reduction process. Varying the amounts of acetone and 2-propanol cosubstrates controls the stereoselectivities of the consecutive oxidation and reduction reactions, respectively. We used one enzyme to accomplish the deracemization of secondary alcohols with up to >99 % ee and >99.5 % recovery in one pot and without the need to isolate the prochiral ketone intermediate.
- Karume, Ibrahim,Takahashi, Masateru,Hamdan, Samir M.,Musa, Musa M.
-
p. 1459 - 1463
(2016/05/02)
-
- Synthesis of raspberry and ginger ketones by nickel boride-catalyzed hydrogenation of 4-arylbut-3-en-2-ones
-
Raspberry and ginger ketones have been synthesized in good yield by the hydrogenation of the corresponding unsaturated precursors 4-(4′- hydroxyphenyl)but-3-en-2-one and 4-(4′-hydroxy-3′-methoxyphenyl)but- 3-en-2-one, respectively, using a freshly prepared suspension of nickel boride in methanol as catalyst.
- Bandarenko, Mikhail,Kovalenko, Vitaly
-
p. 885 - 888
(2014/11/08)
-
- CYCLIC PEROXIDE OXIDATION OF AROMATIC COMPOUND PRODUCTION AND USE THEREOF
-
The present invention provides a method for converting an aromatic hydrocarbon to a phenol by providing an aromatic hydrocarbon comprising one or more aromatic C-H bonds and one or more activated C-H bonds in a solvent; adding a phthaloyl peroxide to the solvent; converting the phthaloyl peroxide to a di-radical; contacting the di-radical with the one or more aromatic C-H bonds; oxidizing selectively one of the one or more aromatic C-H bonds in preference to the one or more activated C-H bonds; adding a hydroxyl group to the one of the one or more aromatic C-H bonds to form one or more phenols; and purifying the one or more phenols.
- -
-
Page/Page column 10
(2014/10/15)
-
- Transfer hydrogenations of alkenes with formate on Pd/C: Synthesis of dihydrocinchona alkaloids
-
Protocols for preparative (1-80 gram scale) transfer hydrogenations of alkenes over a palladium on carbon catalyst using formic acid/ammonium formate as hydrogen donor are presented. Cinchona alkaloids have been converted to their dihydro derivatives in >94% yield. Georg Thieme Verlag Stuttgart - New York.
- Wu, Haotian,Hintermann, Lukas
-
p. 888 - 892
(2013/05/09)
-
- Asymmetric synthesis of enantiomerically pure zingerols by lipase-catalyzed transesterification and efficient synthesis of their analogues
-
The achiral zingerone 1, readily available from ginger, can be easily transformed into chiral derivatives. Zingerol 2, a reduced product of zingerone 1 is expected to be an important new medicinal lead compound. We have achieved a concise synthesis of optically active zingerol (R)-2 and (S)-2 by the lipase-catalyzed stereoselective transesterification of racemic 2. Under the optimized conditions, a lipase from Alcaligenes sp. (Meito QLM) and vinyl acetate in i-Pr2O or hexane at 35 C within 1 h gave the alcohol (S)-2 and the acetate (R)-9 with high enantioselectivity without producing acetylated by-products. Since optically active (S)-2 and (R)-9 were obtained through lipase-catalyzed transesterification, other enantiomerically pure novel compounds could all be synthesized.
- Kitayama, Takashi,Isomori, Sachiko,Nakamura, Kaoru
-
p. 621 - 627
(2013/07/19)
-
- Cephalosporolide B serving as a versatile synthetic precursor: Asymmetric biomimetic total syntheses of cephalosporolides C, E, F, G, and (4-OMe-)G
-
Cephalosporolide B (Ces-B) was efficiently synthesized and exploited for the first time as a versatile biomimetic synthetic precursor for the chemical syntheses of not only cephalosporolides C, G, and (4-OMe-) G via a challenging diastereoselective oxa-Michael addition but also the structurally unprecedented cephalosporolides E and F via a novel biomimetic ring-contraction rearrangement. These findings provide the first direct chemical evidence that Ces-B may be the true biosynthetic precursor of cephalosporolides.
- Song, Liyan,Liu, Yuan,Tong, Rongbiao
-
p. 5850 - 5853
(2013/12/04)
-
- InBr3-catalyzed reduction of ketones with a hydrosilane: Deoxygenation of aromatic ketones and selective synthesis of secondary alcohols and symmetrical ethers from aliphatic ketones
-
An InBr3-Et3SiH reducing system was developed to selectively convert aliphatic ketones to a variety of secondary alcohols in moderate to good yields. An initial mixing of InBr3 and PhSiH 3 was followed by the addition of aliphatic ketones and a solvent to afford the symmetrical ether derivatives.
- Sakai, Norio,Nagasawa, Ken,Ikeda, Reiko,Nakaike, Yumi,Konakahara, Takeo
-
body text
p. 3133 - 3136
(2011/06/26)
-
- Concise enantioselective synthesis of the ten-membered lactone cephalosporolide G and its C-3 epimer
-
A short and highly stereo-selective sequence for the first enantioselective total synthesis of the naturally occurring 10-membered lactone, which was obtained in only eight steps, was reported. The macrolactone ring was carried out by the use of a high-yielding pyridinium chlorochromate (PCC)-mediated oxidative cleavage of a bicyclic intermediate, generated in a domino sequence from a p-peroxyquinol. The synthesis was started with (-)-rhododendrol, which was obtained by enzymatic resolution of the racemic derivative. Phenol (R)-5 was submitted to an oxidative dearomatisation process with singlet oxygen, generated from Oxone in the presence of NaHCO3. The treatment of compound peroxyquinol with para-toluene sulfonic acid followed by Triton B gave, in one step and 49% yield, the tricyclic epoxide bicyclic derivative. A similar route was employed for the synthesis of the C-3 diastereoisomer of the natural product, which was obtained in only 7 steps and 15.2% overall yield.
- Barradas, Silvia,Urbano, Antonio,Carreno, M. Carmen
-
body text
p. 9286 - 9289
(2010/04/03)
-
- Orchestration of concurrent oxidation and reduction cycles for stereoinversion and deracemisation of sec-alcohols
-
Black and white are opposites as are oxidation and reduction. Performing an oxidation, for example, of a sec-alcohol and a reduction of the corresponding ketone in the same vessel without separation of the reagents seems to be an impossible task. Here we show that oxidative cofactor recycling of NADP + and reductive regeneration of NADH can be performed simultaneously in the same compartment without significant interference. Regeneration cycles can be run in opposing directions beside each other enabling one-pot transformation of racemic alcohols to one enantiomer via concurrent enantioselective oxidation and asymmetric reduction employing defined alcohol dehydrogenases with opposite stereo- and cofactor-preference. Thus, by careful selection of appropriate enzymes, NADH recycling can be performed in the presence of NADP+ recycling to achieve overall, for example, deracemisation of sec-alcohols or stereoinversion representing a possible concept for a "green" equivalent to the chemical-intensive Mitsunobu inversion.
- Voss, Constance V.,Gruber, Christian C.,Faber, Kurt,Knaus, Tanja,Macheroux, Peter,Kroutil, Wolfgang
-
supporting information; experimental part
p. 13969 - 13972
(2009/02/07)
-
- Asymmetric synthesis of (R)-(-)-rhododendrol, the aglycone of the hepatoprotective agent rhododendrin
-
Starting from 2,3-O-isopropylidene-D-glyceraldehyde (3) as chiral material, (R)-(-)-rhododendrol 2, the aglycone of the naturally occurring rhododendrin 1 was synthesized. Copyright Taylor & Francis Group, LLC.
- Sabitha, Gowravaram,Thirupathaiah,Yadav
-
p. 1683 - 1688
(2008/02/01)
-
- A chemoselective hydrogenation of the olefinic bond of α,β- unsaturated carbonyl compounds in aqueous medium under microwave irradiation
-
A microwave-assisted mild and ecofriendly catalytic transfer hydrogenation process was developed to reduce various α,β-unsaturated carbonyl compounds into the corresponding saturated carbonyl compounds in the presence of silica-supported palladium chloride as catalyst and a combination of MeOH/HCOOH/H2O (1:2:3) as hydrogen source within 22-55 minutes in moderate to excellent yields with 100% chemoselectivity.
- Sharma, Anuj,Kumar, Vinod,Sinha, Arun K.
-
p. 354 - 360
(2007/10/03)
-
- Resolution of racemic rhododendrol by lipase-catalyzed enantioselective acetylation
-
Both (R)- and (S)-enantiomers of rhododendrol were prepared in high enantiomeric exess by lipase from Pseudomonas cepacia (Amano PS)-catalyzed acetylation of racemic 1 with vinyl acetate at room temperature. Especially, in the case of using acetonitrile as the solvent, by-products 4 and 5 were minimized.
- Yuasa, Yoshifumi,Shibuya, Shiroshi,Yuasa, Yoko
-
p. 1469 - 1475
(2007/10/03)
-
- Efficient production of raspberry ketone via 'green' biocatalytic oxidation
-
For the development of a 'green' oxidation method, the transformation of 4-(p-hydroxyphenyl)butan-2-ol (rhododendrol) into 4-(p-hydroxyphenyl) butan-2-one (raspberry ketone) was used as a model reaction. Different lyophilized cells of Rhodococcus spp. have been screened for their ability to perform the desired oxidation. Rhodococcus equi IFO 3730 and R. ruber DSM 44541 were able to use acetone as a hydrogen acceptor in a hydrogen transfer-like process. The oxidation can be performed at substrate concentrations up to 500 g/L.
- Kosjek, Birgit,Stampfer, Wolfgang,Van Deursen, Ruud,Faber, Kurt,Kroutil, Wolfgang
-
p. 9517 - 9521
(2007/10/03)
-
- Very long-chain phenylpropyl and phenylbutyl esters from Taxus baccata needle cuticular waxes
-
The cuticular wax of Taxus baccata L. needles was found to contain four different classes of long-chain esters that were identified by various chemical transformations with product assignment employing GC-MS. Homologous series of (1) 3-(4′-hydroxyphenyl)-propyl esters of C20-C36 fatty acids, (2) 4-(4′-hydroxyphenyl)-2-butyl esters of C18-C28 fatty acids, (3) 3-(3′,4′-dihydroxyphenyl)-propyl esters of C20-C32 fatty acids, and (4) 4-(3′,4′-dihydroxyphenyl)-2-butyl esters of C18-C28 fatty acids were identified. The four compound classes amounted to 0.1-3.6 μg/cm2 of needle surface area, corresponding to 0.2-7.6% of the wax mixture, respectively. While both phenylpropyl ester series had a maximum for the homolog containing tetracosanoic acid, in the phenylbutyl esters homologs containing eicosanoic and docosanoic acids predominated.
- Jetter, Reinhard,Klinger, Adelheid,Sch?ffer, Stefanie
-
p. 579 - 587
(2007/10/03)
-
- Synthesis and cell growth inhibitory properties of substituted (E)-1-phenylbut-1-en-3-ones
-
A series of (E)-1-phenylbut-1-en-3-ones, based on the naturally occurring (E)-1-(4'-hydroxyphenyl)but-1-en-3-one [IC50 (K562) 60 μM], was synthesised and screened for cytotoxic activity against the K562 human leukaemia cell line. (E)-1-(Pentafluorophenyl)but-1-en-3-one [IC50 (K562) 1.8 μM] was found to be over 30-fold more active than 1.
- Ducki, Sylvie,Hadfield, John A.,Hepworth, Lucy A.,Lawrence, Nicholas J.,Ching-Ying, Liu,McGown, Alan T.
-
p. 3091 - 3094
(2007/10/03)
-
- Stereochemistry of the double bond saturation in the formation in Baker's yeast of 4-(4-hydroxyphenyl)-2-butanone (raspberry ketone)
-
Yeast extract-mediated reduction of 4-(4-hydroxyphenyl)-but-3-en-2-one 3 to raspberry ketone 1 occurs with transfer β to the carbonyl group of H(R) from NADPH and of an hydrogen atom from the solvent at α position, as indicated by experiments with (4R) and (4S) [4-2H]-NADPH and with deuterated solvent. The same extract converts 3 in 1 in the presence of NADH, but much less efficiently. In this latter case H(S) and not H(R) is transferred from the reduced cofactor to position 4 of 1. Horse liver alcohol dehydrogenase-mediated reduction of 1, bearing deuterium labelling at positions 1, 3 and 4 and obtained from 3 using the whole-cell system in the presence of D2O, gave an S carbinol possessing 0.95 ee, shown by 2H NMR studies onto the diacetate 7 to contain an excess of the (3S,4S) diastereoisomer, thus suggesting a prevalent β re-face,syn addition of hydrogen across the double bond of 3 in the whole-cell mediated conversion into 1.
- Fronza, Giovanni,Fuganti, Claudio,Mendozza, Monica,Rallo, Roberta S.,Ottolina, Gianluca,Joulain, Daniel
-
p. 4041 - 4052
(2007/10/03)
-
- Biogeneration and Biodegradation of Raspberry Ketone in the Fungus Beauveria bassiana
-
In growing cultures of the fungus Beauveria bassiana (ATCC 7159) the incubation of 4-(4′-hydroxyphenyl)but-3-en-2-one (p-hydroxybenzylidenacetone, 3), of 4-(4′-hydroxyphenyl)butan-2-one (raspberry ketone, 1), and of the S and R,S forms of 4-(4′-hydroxyphenyl)butan-2-ol (2) yields 2-(4′-hydroxyphenyl)ethanol (tyrosol, 4) as a final product. The experiments support the view that the actual substrate for the Baeyer-Villiger-type degradation is raspberry ketone (1) and that there is a kinetic preference in the microbial enzymatic system for the oxidation to 1 of the S form of the 4-(4′-hydroxyphenyl)butan-2-ol (2).
- Fuganti, Claudio,Mendozza, Monica,Joulain, Daniel,Minut, Jose,Pedrocchi-Fantoni, Giuseppe,Piergianni, Valentino,Servi, Stefano,Zucchi, Gioia
-
p. 3616 - 3619
(2007/10/03)
-
- Isolation of taxol, 10-deacetylbaccatin III and (-)-betuligenol from Taxus baccata Linn.
-
Taxol (1), 10-deacetylbaccatin III (2) (-)-betuligenol (3), p-hydroxybenzaldehyde (4) and betuloside (5) have been isolated from Taxus baccata Linn. of Indian variety.
- Chattopadhyay, S. K.,Tripathi, V. K.,Thakur, R. S.,Sharma, R. P.,Jain, S. P.
-
p. 409 - 411
(2007/10/02)
-
- Catalytic asymmetric induction part 2. Chiral tricarbonyl (η6 arene) chromium (O) complexes as enantioselective catalysts
-
A chiral metallocyclic Lewis acid based catalyst system derived from norephedrine is reported. A key stereodirective element emanates from a tricarbonyl chromium (O) group complexed to the aryl ring. The catalysts mediate the addition of dialkyl zinc species to a variety of aldehydes with high enantioselectivity.
- Jones,Heaton
-
p. 261 - 272
(2007/10/02)
-
- Synthesis of rhododendrin and epi-rhododendrin,
-
The first synthesis of rhododendrin 1 and epi-rhododendrin 2 was achieved by starting from ethyl (S)-3-hydroxybutanoate 4, p-bromoanisole and D-glucose.Rhododendrin 1 is known as the hepatoprotective constituent of Taxus baccata L. Keywords: betuligenol / betuloside / epi-rhododendrin / rhododendrin / rhododendrol
- Mori, Kenji,Qian, Zhao-Hui
-
p. 382 - 387
(2007/10/02)
-
- STEREOCHEMISTRY OF 4-ARYL-2-BUTANOLS FROM HIMALAYAN TAXUS BACCATA
-
4-(4'-Hydroxyphenyl)-2R-butanol, 4-(3',4'-dihydroxyphenyl)-2R-butanol and 4-(3'-methoxy-4'-hydroxyphenyl)-2R-butanol have been isolated from the needles of Himalayan Taxus baccata.These two compounds have not previously been reported in stereospecific forms.Their stereochemistry has been determined by enzymatic reduction of their corresponding 2-butanones.Key Word Index - Taxus baccata; Taxaceae; 4-aryl-2-butanol, stereochemistry; enzymatic reduction; baker's yeast.
- Das, B.,Takhi, M.,Kumar, H. M. Sampath,Srinivas, K. V. N. S.,Yadav, J. S.
-
p. 697 - 700
(2007/10/02)
-
- Absolute Configuration of epi-Rhododendrin and (-)-Rhododendrol and X-Ray Crystal and Molecular Structure of Rhododendrin , a Hepatoprotective Constituent of Taxus baccata
-
Rhododendrin (= betuloside) has been isolated from the leaves of Taxus baccata L.From its X-ray diffraction studies, the absolute configuration at the chiral centre in the aglucone portion has been found to be R.These results establish the stereochemical assignments to different samples of this glucoside isolated from different plants.Our sample of rhododendrin exhibited hepatoprotective activity against two hepatotoxins in rats.
- Parmar, Virinder S.,Vardhan, Anand,Taneja, Poonam,Sinha, Rita,Patnaik, Gyanendra K.,et al.
-
p. 2687 - 2690
(2007/10/02)
-
- Studies on the Constituents of Aceraceae Plants. V. Two Diarylheptanoid glycosides and an Arylbutanol Apiosylglucoside from Acer nikoense
-
From the stem bark of Acer nikoense Maxim. (Aceraceae), three glycosides were isolated, namely aceroside III (1), C30H40O12, mp 138-141 deg C, D -98.4 deg, aceroside VI (2), C25H32O8*1/2H2O, mp 124-125 deg C, D -69.3 deg, and apiosylepirhododendrin (3), amorphous film (C21H32O11), D -59.5 deg.On acid hydrolysis, 1 yielded acerogenin A (4), apiose, glucose, and a partially hydrolyzed product 2, while 3 afforded (+)-rhododendrol (11), apiose, and glucose.Inspection of the carbon-13 nuclear magnetic resonance (13C NMR) and the PRFT-NMR spectra of 1 and 3 disclosed that they are apiosyl-(1->6)-glucosides.The proton nuclear magnetic resonance (1H NMR) spectral data of their permethylates (6 and 12) and the analytical data of methanolysis products of 6 and 12 established the structures of 1, 2 and 3 as acerogenin A 11-O-β-D-apiofuranosyl-(1->6)-β-D-glucopyranoside, acerogenin A 11-O-β-D-glucopyranoside and (+)-rhododendrol 2-O-β-D-apiofuranosyl-(1->6)-β-D-glucanopyranoside, respectively.Keywords - Acer nikoense; Aceraceae; diarylheptanoid; arylbutanol; apiosylglucoside; aceroside (III, VI); apiosylepirhododendrin; (+)-rhododendrol; PRFT-NMR
- Nagai, Masahiro,Kubo, Masayoshi,Takahashi, Kunio,Fujita, Masao,Inoue, Takao
-
p. 1923 - 1928
(2007/10/02)
-
