- Asymmetric Alkylation of Anthrones, Enantioselective Total Synthesis of (?)- and (+)-Viridicatumtoxins B and Analogues Thereof: Absolute Configuration and Potent Antibacterial Agents
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A phase transfer catalyzed asymmetric alkylation of anthrones with cyclic allylic bromides using quinidine- or quinine-derived catalysts is described. Utilizing mild basic conditions and as low as 0.5 mol % catalyst loading, and achieving up to >99:1 dr selectivity, this asymmetric reaction was successfully applied to produce enantioselectively (?)- and (+)-viridicatumtoxins B, and thus allowed assignment of the absolute configuration of this naturally occurring antibiotic. While the developed asymmetric synthesis of C10 substituted anthrones is anticipated to find wider applications in organic synthesis, its immediate application to the construction of a variety of designed enantiopure analogues of viridicatumtoxin B led to the discovery of highly potent, yet simpler analogues of the molecule. These studies are expected to facilitate drug discovery and development efforts toward new antibacterial agents.
- Nicolaou,Liu, Guodu,Beabout, Kathryn,McCurry, Megan D.,Shamoo, Yousif
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supporting information
p. 3736 - 3746
(2017/03/20)
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- Asymmetric direct α-hydroxylation of β-Oxo esters by phase-transfer catalysis using chiral quaternary ammonium salts
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The first enantioselective direct α-hydroxylation of β-oxo esters was developed by using phase-transfer catalysis. 1-Indanone-derived 1-adamantyl (1-Ad) β-oxo esters, in the presence of commercially available cumyl hydroperoxide and a cinchonine-based ammonium salt, resulted in the corresponding products with 69-91 % yield and 65-74 % ee. The reaction had also been successfully scaled-up to a gram quantity, and a similar yield was obtained without loss of the enantioselectivity. Copyright
- Lian, Mingming,Li, Zhi,Du, Jian,Meng, Qingwei,Gao, Zhanxian
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supporting information; experimental part
p. 6525 - 6530
(2011/02/25)
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- Enantioselective phase-transfer-catalyzed intramolecular Aza-Michael reaction: Effective route to pyrazino-indole compounds
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(Chemical Equation Presented) Producing polycycles: A mild and direct stereocontrolled route to pharmacologically active pyrazino-indol-1-ones has been developed. The optimal phase-transfer conditions provide variously functionalized ring-closed compounds
- Bandini, Marco,Eichholzer, Astrid,Tragni, Michele,Umani-Ronchi, Achille
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p. 3238 - 3241
(2008/12/23)
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