- A scalable, Nonenzymatic synthesis of highly stereopure difunctional C4 secondary methyl linchpin synthons
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In response to the continuing widespread use of heterodifunctional C4 secondary methyl building blocks in asymmetric synthesis, we have developed a mole-scale, two-step synthesis of a 1:1 mixture of the diastereomers of 3-bromo-2-methyl-1-propyl camphorsulfonate (casylate). One isomer (2S) has been crystallized to >99:1 dr in ～25% yield. Equilibration of the mother liquor (enriched in 2R) to a 1:1 mixture and recrystallization significantly raises the overall yield of 2S. Applications of 2S include chemoselective Grignard coupling, enabling the very short synthesis of highly stereopure long-chain natural products containing remote, methyl-bearing stereogenic centers [e.g., (R)-tuberculostearic acid], with complete control of configuration. Also, Ag-mediated, completely chemoselective Br displacement from 2S leads to a range of >99:1 er difunctional synthons. Both applications incorporate concurrent recovery of CasO. The enantiomer of 2S can be made from commercial (1R)-10-CasOH.
- Mekala, Shekar,Hahn, Roger C.
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p. 1610 - 1617
(2015/02/19)
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- Synthesis of optically active β- Or γ-alkyl-substituted alcohols through copper-catalyzed asymmetric allylic alkylation with organolithium reagents
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An efficient one-pot synthesis of optically active β-alkyl-substituted alcohols through a tandem copper-catalyzed asymmetric allylic alkylation (AAA) with organolithium reagents and reductive ozonolysis is presented. Furthermore, hydroboration-oxidation following the Cu-catalyzed AAA leads to the corresponding homochiral γ-alkyl-substituted alcohols.
- Guduguntla, Sureshbabu,Fananas-Mastral, Martin,Feringa, Ben L.
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p. 8274 - 8280
(2013/09/24)
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- Haloalkane dehalogenase catalysed desymmetrisation and tandem kinetic resolution for the preparation of chiral haloalcohols
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Six different bacterial haloalkane dehalogenases were recombinantly produced in Escherichia coli, purified, and used to catalyse the conversion of prochiral short-chain dihaloalkanes and a meso dihaloalkane, yielding enantioenriched haloalcohols. A two-reaction one-enzyme process was established in which the desymmetrisation of a dihaloalkane is followed by kinetic resolution of the chiral haloalcohol that is produced in the first step. In case of 1,3-dibromo-2-methylpropane and 1,3-dibromo-2-phenylpropane, an increase of the enantiomeric excess of the respective haloalcohol was observed in time, leading to ee values of >97%, with analytical yields of 24 and 52%, respectively. The results show that haloalkane dehalogenases can be used for the production of highly enantioenriched haloalcohols and that in some cases product enantiopurity can be improved by allowing a two-step one-enzyme tandem reaction.
- Westerbeek, Alja,Van Leeuwen, Jan G.E.,Szymański, Wiktor,Feringa, Ben L.,Janssen, Dick B.
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experimental part
p. 7645 - 7650
(2012/09/21)
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- Scavenger assisted combinatorial process for preparing libraries of tertiary amine compounds
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This invention relates to a novel solution phase process for the preparation of tertiary amine combinatorial libraries. These libraries have utility for drug discovery and are used to form wellplate components of novel assay kits.
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- Ethyl phenylsulfinyl fluoroacetate, a new and versatile reagent for the preparation of α-fluoro-α,β-unsaturated carboxylic acid esters
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The title compound 2 can be alkylated with a wide range of alkyl halides and Michael acceptors. Subsequent thermal elimination of phenyl sulfinic acid 3 leads to α-fluoro-α,β-unsaturated ethyl carboxylates 5 and 10, an important class of intermediates for fluorine containing biologically active compounds.
- Allmendinger, Thomas
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p. 4905 - 4914
(2007/10/02)
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- Intramolecular Nitrile Oxide Cycloaddition (INOC) Reactions in the Indole Series. 2. Total Synthesis of Racemic and Optically Active Paliclavine and 5-epi-Paliclavine
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The first total synthesis of the ergot alkaloid paliclavine and the formal total synthesis of paspaclavine in optically active form are described.
- Kozikowski, Alan P.,Chen, Yon-Yih
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p. 5248 - 5250
(2007/10/02)
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