China
Africa
Explore chapters and articles related to this topic
Cipargamin: Biocatalysis in the Discovery and Development of an Antimalarial Drug
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Thomas Ruch, Elina Siirola, Radka Snajdrova
Initially, ketone 13 was formed as a minor side product (circa 4%) in the racemic route (via a Nef reaction of partly reduced 3) and hence experiments were carried out to see whether variation of the reaction conditions could be identified which would favor the formation of this key intermediate. Indeed, it was possible to increase the yield of ketone 13% up to 68%, however, the synthesis gained extra step. An alternative proposal was suggested starting from fluoro, chloro-isatin rather than fluoro, chloro-indole, and using its properties of an “umpoled” indole, for introduction of ketone moiety (Scheme 15.10; in analogy to Garden et al., 2002). An Aldol reaction with acetone would introduce the required sidechain. Reduction with borane converted the oxindole ring to the required indole system; however, concurrent reduction of the ketone to the corresponding racemic alcohol occurred. It became necessary to introduce an oxidative step to provide the desired ketone 13 (Scheme 15.8). Initially envisaged synthesis to ketone 13.
Catalytic Asymmetric Synthesis of Aryl-Fused Heterocycles via Cascade Reactions of Nitroalkenes
Published in Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera, Catalytic Asymmetric Reactions of Conjugated Nitroalkenes, 2020
Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera
Later, the same group reported a one-pot organocatalytic synthetic strategy toward biologically potent natural product scaffold aflatoxins 41 (Scheme 11.17).15 By utilizing the four-step protocol involving Michael-acetalization of nitroalkenes 1b and aldehyde 40 followed by reduction and Nef reaction delivered dihydroaflatoxin D2 and aflatoxin B2. They have also demonstrated the total synthesis of a natural product (+) and (−)-microminutinin using this protocol.
Microwave-Assisted Synthesis and Functionalization of Six-Membered Oxygen Heterocycles
Published in Banik Bimal Krishna, Bandyopadhyay Debasish, Advances in Microwave Chemistry, 2018
Neha Batra, Rahul Panwar, Ramendra Pratap, Mahendra Nath
Kaneria et al. synthesized 3-aryl-furo[3,2-c]coumarins by using two different microwave-assisted methodologies [154]. In the first protocol, they have reacted various 4-hydroxycoumarins with 2-aryl-1-nitroethenes under Nef reaction conditions whereas, in another protocol, 4-hydroxycoumarins were reacted with aroylmethylbromides under Feist-Benary reaction conditions to yield various 3-aryl-furo[3,2-c]coumarins (Scheme 5.51).
A review on DBU-mediated organic transformations
Published in Green Chemistry Letters and Reviews, 2022
Shashi Kanth Boddu, Najeeb Ur Rehman, Tapan Kumar Mohanta, Anjoy Majhi, Satya Kumar Avula, Ahmed Al-Harrasi
Selective Nef reaction of different secondary nitro compounds has been converted into the corresponding ketones under basic conditions using DBU in acetonitrile. In this reaction, DBU acts a base (Scheme 50) (67).