- Enantioselective Total Synthesis of the Archaeal Lipid Parallel GDGT-0 (Isocaldarchaeol)**
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Archaeal glycerol dibiphytanyl glycerol tetraethers (GDGT) are some of the most unusual membrane lipids identified in nature. These amphiphiles are the major constituents of the membranes of numerous Archaea, some of which are extremophilic organisms. Due to their unique structures, there has been significant interest in studying both the biophysical properties and the biosynthesis of these molecules. However, these studies have thus far been hampered by limited access to chemically pure samples. Herein, we report a concise and stereoselective synthesis of the archaeal tetraether lipid parallel GDGT-0 and the synthesis and self-assembly of derivatives bearing different polar groups.
- Falk, Isaac D.,Gál, Bálint,Bhattacharya, Ahanjit,Wei, Jeremy H.,Welander, Paula V.,Boxer, Steven G.,Burns, Noah Z.
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supporting information
p. 17491 - 17496
(2021/06/15)
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- A novel highly enantio- and diastereoselective synthesis of vitamin e side-chain
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A novel highly enantioselective (>99% ee) and diastereoselective (>98% de) method for the synthesis of chiral C15 vitamin E side-chain 1 was developed. ZACA-lipase-catalyzed acetylation protocol to provide a key α,ω-dioxyfunctional C5/sub
- Matsueda, Yohei,Xu, Shiqing,Negishi, Ei-Ichi
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p. 3346 - 3348
(2015/06/02)
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- Tocopherol side chain synthesis via asymmetric organocatalytic transfer hydrogenation and convenient measurement of stereoselectivity
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An asymmetric synthetic route for 1-iodofarnesane, a key intermediate for tocopherol side chain synthesis, starting from (+)-(R)-citronellal was developed. 1-Iodofarnesane was prepared through eight steps in about 50% overall yield, and asymmetric transfe
- Lee, Hyunji,Lee, You-Kyoung,Kim, Dong-Guk,Son, Mi-Sun,Nam, Tae-Gyu,Jeong, Byeong-Seon
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p. 5895 - 5897
(2014/12/12)
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- Enantio- and diastereoselective hydrogenation of farnesol and O-protected derivatives: Stereocontrol by changing the C=C bond configuration
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(Chemical Presented) Four isomers-one catalyst: The four stereoisomers of hexahydrofarnesol can be prepared with high enantio- and diastereoselectivity by using the same chiral iridium catalyst 1 with different cis/trans isomers of farnesol (see scheme; B
- Wang, Aie,Wuestenberg, Bettina,Pfaltz, Andreas
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p. 2298 - 2300
(2008/12/23)
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- ASYMMETRIC HYDROGENATION OF ALKENNES USING CHIRAL IRIDIUM COMPLEXES
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The invention relates to the (stereoselective) hydrogenation of carbon-carbon double bonds in compounds having at least one such bond, e.g., isoprenoids, non-cyclic sesquiterpenes, tocomonoenols, tocodienols, tocotrienols or derivatives thereof, as well as to the (stereoselective) hydrogenation of parts/extracts of plant oils containing such tocotrienols or derivatives thereof, in the presence of a chiral Ir complex as the catalyst, whereby preferably one stereoisomer is manufactured in an excess.
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Page/Page column 19
(2008/06/13)
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- Stereocontrol of 1,5-related stereocentres using an intermediate silyl group-the diastereoselectivity of nucleophilic attack on a double bond adjacent to a stereogenic carrying a silyl group
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R-5-Methylcyclohex-2-enone 1 reacts successively with the phenyldimethylsilylzincate reagent and acetaldehyde to give with regiocontrol the aldols 7, dehydration of which creates the E-exocyclic double bond of the α-β-unsaturated ketone 2. Conjugate addition of the ethylcuprate reagent to this compound takes place with high (96 : 4) selectivity in favour of the R stereoisomer 12, hydrolysis of which gives (2R,3R,5S,2′ R)-2-(but-2′-yl)-3-dimethyl(phenyl)silyl-5-methylcyclohexanone 3. The oxime acetate of this ketone undergoes fragmentation in the presence of trimethylsilyl trifluoromethanesulfonate to give 3R,7R,5E-3,7-dimethylnon-5-enonitrile 4, in which an open-chain 1,5-stereo-chemical relationship is set up with a high level of stereocontrol. A similar sequence adding 4-methylpentylcuprate to the enone 2, and fragmentation gives 3R,7R,5E-3,7,11-trimethyldodec-5-enonitrile 20. Reduction and hydrogenation of this nitrile gives 3R,7R-3,7,11 -trimethyldodecanal 22, which can be converted into phytol 25. The ketoaldehyde 29 reacts with samarium iodide to give only the alcohol 30, in which the radical anion has attacked from the top surface, just like the cuprate reagents in their reactions with the ketone 2.
- Fleming, Ian,Maiti, Pranab,Ramarao, Chandrashekar
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p. 3989 - 4004
(2007/10/03)
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- A new protocol for the enantioselective synthesis of methyl-substituted alkanols and their derivatives through a hydroalumination/zirconium-catalyzed alkylalumination tandem process
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Methyl-substituted alkanols have been synthesized enantioselectively (90-93% ee) in a one-pot hydroalumination/carboalumination tandem process (see scheme). This enantioselectively represents an increase of about 15% from the previously attainable ee values. DIBAH = diisobutylaluminum hydride, IBAO = isobutylaluminoxane.
- Huo, Shouquan,Shi, Ji-Cheng,Negishi, Ei-Ichi
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p. 2141 - 2143
(2007/10/03)
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- Enantioselective synthesis of (2R,4'R,8'R)-α-tocopherol (Vitamin E) based on enzymatic function
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Syntheses of (S)-chroman-2-carboxaldehyde congener 1 and (S)-chiral isoprene unit 3 were achieved based on the enzymatic acetylation of (±)- chroman-2-methanol 6 and (±)-(2,3)-anti-2-methyl-3-(p-methoxyphenyl)-1,3- propane diol 12, respectively. Synthesis of the side-chain part corresponding to (3R,7R)-3,7,11-trimethyldodecan-1-ol 27 was achieved by the coupling reaction of (S)-3 and (R)-3,7-dimethyloctyl iodide 4. The Wittig reaction of (3R,7R)-phosphonium salt 2 derived from (3R,7R)-27 and (S)-1 gave the olefin 28 which was subjected to catalytic hydrogenation to afford (2R,4'R,8'R)-α- tocopherol.
- Nozawa, Masako,Takahashi, Keiko,Kato, Keisuke,Akita, Hiroyuki
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p. 272 - 277
(2007/10/03)
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- Synthesis of archaebacterial lipid C20 chirons
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Archaebacterial lipid C20 chirons were synthesized by cross-coupling optically active C10 'dimer' units prepared from hydroxyester 7. Vitamin E (C15) side chain was similarly constructed.
- Berkowitz, William F.,Yanzhong, Wu
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p. 8141 - 8144
(2007/10/03)
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- A synthesis of (2R,4'R,8'R)-α-tocopherol (vitamin E) side chain
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Optically pore (3R,7R)-3,7,11-trimethyldodecan-1-ol (16), corresponding to the α-tocopherol side chain, was synthesized by the coupling reaction of a chiral isoprene unit (3S)-9 derived from an enzymatically hydrolyzed product (2S,3S)-2 and a ten-carbon alkylating reagent (R)-13 derived from (R)-(+)-pulegone.
- Chen, Cheng Yu,Nagumo, Shinji,Akita, Hiroyuki
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p. 2153 - 2156
(2007/10/03)
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- New efficient methods for the synthesis and in-situ preparation of ruthenium(II) complexes of atropisomeric diphosphines and their application in asymmetric catalytic hydrogenations
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A new synthetically useful method for the synthesis of the diphosphine ruthenium dicarboxylato complexes (P-P)Ru(O2CR)2(R= CF3 and CH3) is presented, which uses the easily accessible complex (COD)2Ru2(μ-O2CCF3)4 as starting material. This complex as well as (COD)(Ru(ηO2CCH3)2 and (COD)2Ru2Cl4(NCCH3) have been shown to be suitable precursor complexes for the in-situ preparation of ruthenium(II) dicarboxylato and dichloro complexes of atropisomeric diphosphines, respectively. The high efficacy of the preformed and in-situ generated ruthenium complexes as precatalysts is demonstrated in asymmetric hydrogenations of allylic alcohols, enamides, and a β-keto ester.
- Heiser,Broger,Crameri
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- Process for producing optically active alcohols
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A process for producing an optically active alcohol represented by formula (I): STR1 wherein R1 is an alkyl group having from 2 to 11 carbon atoms, an alkenyl group having from 3 to 11 carbon atoms, an alkadienyl group having from 6 to 11 carbon atoms, a cyclohexyl group, an cyclohexylmethyl group, or a cyclohexylethyl group, provided that the olefin in the alkenyl group or alkadienyl group is not conjugated to the olefin at the 2-position thereof; and * means an asymmetric carbon atom, is disclosed, comprising subjecting an olefinic alcohol represented by formula (II): STR2 wherein R1 is the same as defined above to asymmetric hydrogenation in the presence of, as a catalyst, a ruthenium-optically active phosphine complex. According to the process of the invention, the desired optically active alcohols which are useful not only as intermediates for the manufacture of perfumes and vitamin E but also as liquid crystal materials can be produced with high optical purities.
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- New syntheses of optically active vitamin E side chain by chemicoenzymatic approach
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Two independent syntheses of enantiomerically pure ( 3R, 7R) -3,7,11-tri-methyldodecan-1-ol (2a), the C15 tocopherol side chain, are described. Both reaction sequences start from (R)-citrohellol, obtained by baker's yeast reduction of geraniol. One strategy is based on the coupling between (R)-citronellyl bromide and a C5 optically active unit derived from chemical degradation of the common starting template; the other one uses an achiral isoprenic unit and a C10, building block containing two asymmetric carbon atoms generated by microbial reactions.
- Gramatica,Manitto,Monti,Speranza
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p. 6687 - 6692
(2007/10/02)
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- Chirality Transfer in Stereoselective Synthesis. A Highly Stereoselective Synthesis of Optically Active Vitamin E Side Chains
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Employing the Carroll reaction as a means of chirality transfer, a highly efficient, stereochemically controlled, and generally applicable synthesis of optically active 1,5-dimethylated acyclic chains has been developed; as an example, the synthesis of the optically active C-15 vitamin E side chains 7a and 7b from (+)-pulegone in 12.6percent and 11.7percent overall yields, respectively, is described.
- Koreeda, Masato,Brown, Lindsey
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p. 2122 - 2124
(2007/10/02)
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- Process for the manufacture of tertiary, optically active aliphatic compounds
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A process for asymmetrically hydrogenating through the use of microorganisms a double bond connected to tertiary carbon atom in an olefinic aliphatic compound to produce a tertiary, optically active aliphatic compound useful as an intermediate for optically active Vitamins E and K.
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- A STEREOCONTROLLED TOTAL SYNTHESIS OF OPTICALLY ACTIVE (R,R)-PHYTOL
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A stereospecific synthesis of (R,R)-phytol with highly stereochemical purity in both absolute and geometrical configurations was achieved by utilizing the SN2 type ring-opening reaction of (R)-β-methyl-β-propiolactone, and the SN2' type ring-opening reaction of isopropenyl oxirane, from (R)-pulegone as a starting material.
- Fujisawa, Tamotsu,Sato, Toshio,Kawara, Tatsuo,Ohashi, Kazuo
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p. 4823 - 4826
(2007/10/02)
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- Antioxidant chroman compounds
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The (6-hydroxy-chroman-2-yl) acetic or carboxylic acid derivatives useful as antioxidants and a method for preparing these derivatives from hydroquinones and intermediates in this synthesis as well as the use of these derivatives as intermediates in the preparation of optically active alpha-tocopherol.
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