- Lewis Base–Br?nsted Acid–Enzyme Catalysis in Enantioselective Multistep One-Pot Syntheses
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Establishing one-pot, multi-step protocols combining different types of catalysts is one important goal for increasing efficiency in modern organic synthesis. In particular, the high potential of biocatalysts still needs to be harvested. Based on an in-depth mechanistic investigation of a new organocatalytic protocol employing two catalysts {1,4-diazabicyclo[2.2.2]octane (DABCO); benzoic acid (BzOH)}, a sequence was established providing starting materials for enzymatic refinement (ene reductase; alcohol dehydrogenase): A gram-scale access to a variety of enantiopure key building blocks for natural product syntheses was enabled utilizing up to six catalytic steps within the same reaction vessel.
- Giesler, Markus,Guder, Marian,Hartmann, Laura,Mantel, Marvin,Pietruszka, J?rg,Rüthlein, Elisabeth
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p. 16700 - 16706
(2021/05/07)
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- Stereocontrolled total synthesis of (+)-concanamycin F: The strategic use of boron-mediated aldol reactions of chiral ketones
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A highly stereocontrolled total synthesis of the 18-membered macrolide (+)-concanamycin F, a potent inhibitor of vacuolar ATPases, is described that proceeds in 5.8% yield over 26 steps. The three key fragments, C1-C13 vinyl iodide, C14-C22 vinyl stannane
- Paterson, Ian,Steadman Neé Doughty, Victoria A.,McLeod, Malcolm D.,Trieselmann, Thomas
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p. 10119 - 10128
(2012/01/14)
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- Asymmetric total synthesis of (-)-callystatin A employing the SAMP/RAMP hydrazone alkylation methodology
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(equation presented) The asymmetric total synthesis of (-)-callystatin A has been achieved. The key steps generating the stereogenic centers rely on the asymmetric α-alkylation of aldehydes or ketones exploiting the SAMP/RAMP hydrazone alkylation methodology, as well as an enzymatic enantioselective reduction of a 3,5-dioxocarboxylate. For the construction of the alkene moieties, highly selective Wittig or Horner-Wadsworth-Emmons reactions were employed.
- Vicario, Jose L.,Job, Andreas,Wolberg, Michael,Mueller, Michael,Enders, Dieter
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p. 1023 - 1026
(2007/10/03)
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- Asymmetric total synthesis of (-)-callystatin A and (-)-20-epi-callystatin A employing chemical and biological methods
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An efficient asymmetric total synthesis of the potent cytotoxic marine natural product (-)-callystatin A and its 20-epi analogue has been achieved. The synthetic pathway involved the preparation of three fragments to be coupled with each other at the end of the route. The first fragment 3 was obtained using a biocatalytic enantioselective reduction of a 3,5-dioxocarboxylate as the key step. For the second intermediate 4 the asymmetric α-alkylation of an O-protected derivative of 4-hydroxybutanal was performed exploiting the SAMP/ RAMP hydrazone alkylation methodology, and followed by a highly Z-selective Homer-Wadsworth-Emmons reaction under modified conditions. For the synthesis of the polypropionate fragment 5 a diastereoselective syn-aldol reaction was employed between a chiral ethyl ketone and an α-substituted chiral aldehyde, both prepared in enantiopure form again by means of the asymmetric alkylation of their corresponding RAMP hydrazones. Finally, these three building blocks were coupled using highly E-selective Wittig reactions via allyltributylphosphonium ylides to afford the target compounds after a final oxidation/deprotection sequence.
- Enders, Dieter,Vicario, Jose L.,Job, Andreas,Wolberg, Michael,Mueller, Michael
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p. 4272 - 4284
(2007/10/03)
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- Versatile enantioselective synthesis of four diastereomers of serricornin, a sex pheromone of the cigarette beetle, using the SAMP/RAMP-hydrazone method
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Serricornin is a female-produced sex pheromone of the cigarette beetle (Lasioderma serricorne), which is a pest of dried foodstuffs and tobacco. We report a versatile and short synthesis of all possible 6,7-syn-isomers of serricornin, including the natura
- Job, Andreas,Nagelsdiek, Rene,Enders, Dieter
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p. 524 - 538
(2007/10/03)
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- ASYMMETRIC ALDOL REACTIONS USING CHIRAL BORON REAGENTS: APPLICATION TO THE SYNTHESIS OF TIRANDAMYCIN A
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The bicyclic acetal 1, a key intermediate in previous synthetic studies on tirandamycin A, has been prepared in enantiomerically pure form starting from the (R)-ethylketone 2 and the aldehyde 3.A reagent controlled aldol reaction using (-)-(Ipc)2BOTf sele
- Paterson, Ian,Lister, M. Anne,Ryan, Glen R.
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p. 1749 - 1752
(2007/10/02)
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- ALDOL CONDENSATIONS OF CHIRAL ETHYLKETONES: CONTROL BY CHIRAL BORON REAGENTS.
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The chiral reagents (+)- and (-)-(Ipc)2BOTf, in the presence of Et3N, are used to control the aldol condensation reactions of chiral ethylketone 5 with prochiral aldehydes.The SS isomer, 6 or 8, or SA isomer, 7 or 9, is then formed in >99 percentee and wi
- Paterson, Ian,Lister, Anne M.
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p. 585 - 588
(2007/10/02)
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