- Versicolactones A and B: Total synthesis and structure revision
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To further determine absolute configurations of versicolactones A and B, total synthesis of versicolactones A and B and their six stereoisomers were reported in this Letter. The 1H and 13C NMR spectra of the synthetic erythro-stereoisomers matched perfectly with those of the natural products. Combined with the comparison of the specific rotations, the absolute configuration of versicolactones A and B were revised as (4Z,6R,7S)- and (4E,6R,7S)- from the corresponding (4Z,6R,7R)- and (4E,6R,7R)-6,7-dihydroxyocta- 2,4-dien-4-lactone, respectively.
- Wang, Liping,Zhu, Weiming
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- On the selectivity of oxynitrilases towards α-oxygenated aldehydes
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Different α-alkoxy and α,β-di-alkoxy substituted aldehydes have been submitted to the catalytic action of the oxynitrilases from almond (PaHNL) or from Hevea brasiliensis (HbHNL), in order to explore the possibility of using these enzymes for the preparation of complex cyanohydrins. The selectivity of both enzymes towards these compounds was found to be largely dependent on the substitutents, being low with the aldehydes carrying the sterically more demanding phenyl substituent. Contrary to the chemical addition of HCN, which always occurs with a slight preference for the formation of the anti diastereoisomers, the enzymatic cyanuration - occurring with a facial preference, Si or Re according to the biocatalyst used - gave a mixture of cyanohydrins that, depending on the starting enantiomeric aldehyde, can be enriched in the syn diastereoisomers.
- Bianchi, Paola,Roda, Gabriella,Riva, Sergio,Danieli, Bruno,Zabelinskaja-Mackova, Antonina,Griengl, Herfried
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- The revised structure of trichodermatide A
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A revised structure for trichodermatide A, which is a C10 epimer of the originally reported structure, is proposed. The revision is supported by the X-ray structure of a synthetic intermediate synthesized according to our previous route for trichodermatide A. The revised stereochemistry was also supported by NOESY experiment. Finally, we synthesized Trauner's compound corresponding to the originally reported structure from our synthetic intermediate of trichodermatide A through a Mitsunobu reaction at C10. A revised structure for trichodermatide A is proposed. The revision is supported by the X-ray structure of a synthetic intermediate synthesized according to our previous route for trichodermatide A. The revised stereochemistry was also supported by NOESY experiment. Finally, we synthesized Trauner's compound corresponding to the originally reported structure from our synthetic intermediate of trichodermatide A through a Mitsunobu reaction at C10.
- Shigehisa, Hiroki,Kikuchi, Harue,Suzuki, Tsuyoshi,Hiroya, Kou
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- Stereoselective synthesis of 1,2-13C2-L-fucose, 1,2-13C2-fucono-γ-lactone and 1,2- 13C2-fucono-γ-lactol from non-sugar starting material
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An efficient synthesis is reported for the preparation of L-fucose, and of L-fucofuranose, from 1. The route is designed to facilitate 13C labelling at C1 and/or C2, and the synthesis of 1,2-13C 2-fucose as its tetraacetate is described. The C2 and C3 stereo-centres are introduced using asymmetric dihydroxylation, and the lactone ring size resulting from cyclisation of 4 was controlled to provide the L-fucofuranone 5, whose structure was unambiguously established by X-ray crystal analysis of the derived trisilyl ether 6. Generation of the fucose lactol 7 by reduction of 6 followed by deprotection then provided L-fucose, isolated as its peracetate 8. Georg Thieme Verlag Stuttgart.
- Gardiner, John M.,Panchal, Nitesh R.,Stimpson, William T.,Herbert, John M.,Ellames, George J.
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- Enantioselective sensing of insect pheromones in water
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An arrayed combination of water-soluble deep cavitands and cationic dyes has been shown to optically sense insect pheromones at micromolar concentration in water. Machine learning approaches were used to optimize the most effective array components, which
- Chen, Junyi,Gill, Adam D.,Hickey, Briana L.,Hooley, Richard J.,Millar, Jocelyn G.,Zhong, Wenwan,Zou, Yunfan
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supporting information
p. 13341 - 13344
(2021/12/17)
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- On the origins of diastereoselectivity in the conjugate additions of the antipodes of lithium N-benzyl-(N-α-methylbenzyl)amide to enantiopure cis- and trans-dioxolane containing α,β-unsaturated esters
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"Matching" and "mismatching" effects in the doubly diastereoselective conjugate additions of the antipodes of lithium N-benzyl-(N-α-methylbenzyl)amide to enantiopure cis- and trans-dioxolane containing α,β-unsaturated esters have been investigated. High levels of substrate control were established first upon conjugate addition of achiral lithium N-benzyl-N-isopropylamide to both tert-butyl (S,S,E)-4,5-O- isopropylidene-4,5-dihydroxyhex-2-enoate and tert-butyl (4R,5S,E)-4,5-O- isopropylidene-4,5-dihydroxyhex-2-enoate. However, upon conjugate addition of lithium (R)-N-benzyl-(N-α-methylbenzyl)amide and lithium (S)-N-benzyl-(N-α-methylbenzyl)amide to these substrates, neither reaction pairing reinforced the apparent sense of substrate control. These reactions do not, therefore, conform to the classical doubly diastereoselective "matching" or "mismatching" pattern usually exhibited by this class of reaction. A comparison of these reactions with the previously reported doubly diastereoselective conjugate addition reactions of lithium amide reagents to analogous substrates is also discussed.
- Davies, Stephen G.,Foster, Emma M.,Frost, Aileen B.,Lee, James A.,Roberts, Paul M.,Thomson, James E.
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p. 6186 - 6200
(2012/09/05)
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- Synthesis and bioluminescence-inducing properties of autoinducer (S)-4,5-dihydroxypentane-2,3-dione and its enantiomer
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The autoinducer (4S)-4,5-dihydroxypentane-2,3-dione ((S)-DPD, AI-2) facilitates chemical communication, termed 'quorum sensing', amongst a wide range of bacteria, The synthesis of (S)-DPD is challenging in part due to its instability. Herein we report a novel synthesis of (S)-DPD via (2S)-2,3-O-isopropylidene glyceraldehyde, through Wittig, dihydroxylation and oxidation reactions, with a complimentary asymmetric synthesis to a key precursor. Its enantiomer (R)-DPD, was prepared from d-mannitol via (2R)-2,3-O-isopropylideneglyceraldehyde. The synthesized enantiomers of DPD have AI-2 bioluminescence-inducing properties in the Vibrio harveyi BB170 strain.
- Kadirvel, Manikandan,Stimpson, William T.,Moumene-Afifi, Souad,Arsic, Biljana,Glynn, Nicola,Halliday, Nigel,Williams, Paul,Gilbert, Peter,McBain, Andrew J.,Freeman, Sally,Gardiner, John M.
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scheme or table
p. 2625 - 2628
(2010/07/13)
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- Total synthesis of (+)-varitriol
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The total synthesis of natural (+)-varitriol (1) was accomplished by starting from dimethyl L-tartrate. The key features were a substrate selective and diastereoselective PdII-catalysed bicyclisation of unsaturated protected triol 9 followed by regioselective ring-opening of bicyclic skeleton 10. The absolute configuration of the target was confirmed by single-crystal X-ray analysis for the first time.
- Palik, Miroslav,Karlubikova, OL'Ga,Lasikova, Angelika,Kozisek, Jozef,Gracza, Tibor
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scheme or table
p. 709 - 715
(2009/07/19)
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- The use of π-allyltricarbonyliron lactone complexes in the synthesis of the resorcylic macrolides α- and β-zearalenol
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A highly stereoselective synthesis of the natural products α- and β-zearalenol 1 and 2 has been achieved using π-allyltricarbonyliron lactone complexes to control the 1,5-stereochemical relationship of the oxygen functionalities found in these resorcylic macrolides.
- Burckhardt, Svenja,Ley, Steven V.
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p. 874 - 882
(2007/10/03)
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- The use of π-allyltricarbonyliron lactone complexes in the synthesis of the resorcylic macrolides α- and β-zearalenol
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A highly stereoselective synthesis of α- and β-zearalenol 1 and 2 is accomplished utilising π-allyltricarbonyliron lactone complexes 5 and 6 to establish the 1,5-stereochemical relationship of oxygen functionalities present in the natural products. The Royal Society of Chemistry 2000.
- Ley, Steven V.,Burckhardt, Svenja
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p. 3028 - 3030
(2007/10/03)
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- Synthesis and use of a new synthon: 4-bromo-4-deoxy-L-threonic acid methyl ester
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The action of the system PPh3-CBr4 on the 3,4-O-isopropylidene-L-threonic acid methyl ester, obtained from L-ascorbic acid, provides a new 4-bromo threonic derivative with a good yiled.This new compound is an useful intermediate for the synthesis of various natural products as dihyromahubanolide or anthopleurine.Keywords - L-ascorbic acid / threonic ester / bromination
- Mayer, P.,Ahond, A.,Poupat, C.,Potier, P.
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p. 509 - 512
(2007/10/02)
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- 2,3,4,9-Tetrahydrothiopyranoindoles: Synthesis via an Intramolecular Indole Grignard Reaction and Conformational Study by 1H and 13C NMR Spectroscopy
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Cycloalkylation reactions of 2-alkylthioindoles (2; X = OSO2R, halogens, or epoxy) to 2,3,4,9-tetrahydrothiopyranoindoles (3) via the corresponding metallated indole intermediates have been studied.Compound (2) could be cyclized to (3) in good yiel
- Ishizuka, Natsuki
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p. 813 - 826
(2007/10/02)
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- STEREOSELECTIVE CONDENSATION OF BIS-p-TOLYLTHIOMETHANE WITH LACTIC ACID DERIVATIVES THROUGH AN ACYLATION-REDUCTION STRATEGY: SYNTHESIS OF PROTECTED 4-DEOXY-L-THREOSE AND 4-DEOXY-L-ERYTHROSE
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The condensation of lithium bis-p-tolylthiomethanide with protected ethyl-L-lactates gave a series of 3-alkoxy- (or 3-hydroxy-) 1,1-bis-p-tolylthiobutan-2-ones, which were stereoselectively reduced to the corresponding syn- or anti-alcohols with diastereo
- Guanti, Giuseppe,Banfi, Luca,Guaragna, Alberto,Narisano, Enrica
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p. 2369 - 2376
(2007/10/02)
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- THE CHEMISTRY OF SILYLATED KETENE ACETALS: AN EFFICIENT STEREOCONTROLLED SYNTHESIS OF N-BENZOYL L-DAUNOSAMINE
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N-Benzoyl L-daunosamine was synthesized with high stereoselectivity utilizing a 1,3-addition of ketene silyl acetal (3a) to the chiral nitrone, (Z)-((4R)-trans-2,2,5-trimethyl-1,3-dioxolan-4-yl)methylene((1S)-1-phenylethyl)amine N-oxide (4c) accompanied by a silyl group-transfer in acetonitrile under mild conditions.
- Kita, Yasuyuki,Itoh, Fumio,Tamura, Osamu,Ke, Ya Yuan,Tamura, Yasumitsu
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p. 1431 - 1434
(2007/10/02)
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- ENANTIOMERIC β-ANGELICA LACTONE EPOXIDES: THEIR SYNTHESES FROM SUITABLE CHIRAL PRECURSORS AND THEIR USE IN THE PREPARATION OF BLASTMYCINONE
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Syntheses of (S)-β-angelica lactone from L-tartaric acid and (R)-γ-hydroxymethyl-γ-butyrolactone, 5, are reported.Alternative routes to prepare 5 from S- and R-glutamic acids and D-ribonolactone, respectively, are also presented.Epoxides derived from (R)-
- Ortuno, Rosa M.,Alonso, Daniel,Cardellach, Jaume,Font, Josep
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p. 2191 - 2198
(2007/10/02)
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- Preparation of (4R,5S)-(5-methyl-2,2-dimethyl-1,3-dioxolane-4-ylmethyl)-phosphonium iodide. A synthetic approach to olguine: further model studies
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The enantiomerically pure title compound ((4R,5S)-(5-methyl-2,2-dimethyl-1,3-dioxolane-4-ylmethyl)-phosphonium iodide) has been synthesized starting from (R,R)-(+)-tartaric acid.The synthesis of an oliguine analog has been carried out.Attempts have been made to improve the stereoselectivity and yield of key steps.
- Valverde, Serafin,Herradon, Bernardo,Rabanal, Rosa M.,Martin-Lomas, Manuel
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p. 332 - 338
(2007/10/02)
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- Asymmetric Dihydroxylations of β-Substituted N-(α,β-Enolyl)bornane-10,2-sultams
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Pure (E)- or (Z)-enoylsultams 2 were oxidized with OsO4/N-methylmorpholine N-oxide in a stereospecific and highly ?-face selective manner.Acetalization of the resulting 1,2-diols furnished, after purification, the stable, crystalline acetals 6 in >99percent d.e. and in 63-74percent overall yield from 2.Reductive or hydrolytic cleavage of 6 gave enantiometrically pure alcohols 8 or carboxylic acids 9 with recovery of the sultam auxiliary 1.
- Oppolzer, Wolfgang,Barras, Jean-Pierre
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p. 1666 - 1675
(2007/10/02)
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- Enantiospecific Synthesis of Protected 4-Deoxy-L-threose and 4-Deoxy-L-erythrose via Diastereoselective Reduction of L-Lactic Acid-derived Ketones
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The title compounds were synthesized from L-lactic acid via an acylation-reduction sequence employing lithium bis-p-tolylthiomethanide as a formyl anion equivalent.
- Guanti, Giuseppe,Banfi, Luca,Narisano, Enrica
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p. 136 - 138
(2007/10/02)
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- Synthesis of aliphatic nucleoside analogues with potential antiviral activity
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The synthesis of a series of double-modified adenosine and 8-aza-adenosine analogues, altered in the 6-position of the base and having the sugar moiety replaced by an acyclic hydroxylated side chain is described. Also, some aliphatic derivatives of 5-iodo- and E-5-(2-bromovinyl)uracil were prepared. Of all these compounds, only 6-hydroxylamino-9-(2,3-dihydroxypropyl)purine displayed some antiviral activity when tested in primary rabbit kidney cell cultures against vesicular stomatitis, vaccinia or herpes simplex virus.
- Colla,Busson,De Clercq,Vanderhaeghe
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p. 569 - 576
(2007/10/02)
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