68900-05-0Relevant academic research and scientific papers
Electroreductive Carbofunctionalization of Alkenes with Alkyl Bromides via a Radical-Polar Crossover Mechanism
Zhang, Wen,Lin, Song
supporting information, p. 20661 - 20670 (2020/12/23)
Electrochemistry grants direct access to reactive intermediates (radicals and ions) in a controlled fashion toward selective organic transformations. This feature has been demonstrated in a variety of alkene functionalization reactions, most of which proceed via an anodic oxidation pathway. In this report, we further expand the scope of electrochemistry to the reductive functionalization of alkenes. In particular, the strategic choice of reagents and reaction conditions enabled a radical-polar crossover pathway wherein two distinct electrophiles can be added across an alkene in a highly chemo- and regioselective fashion. Specifically, we used this strategy in the intermolecular carboformylation, anti-Markovnikov hydroalkylation, and carbocarboxylation of alkenes - reactions with rare precedents in the literature - by means of the electroreductive generation of alkyl radical and carbanion intermediates. These reactions employ readily available starting materials (alkyl halides, alkenes, etc.) and simple, transition-metal-free conditions and display broad substrate scope and good tolerance of functional groups. A uniform protocol can be used to achieve all three transformations by simply altering the reaction medium. This development provides a new avenue for constructing Csp3-Csp3 bonds.
De novo Biosynthesis of “Non-Natural” Thaxtomin Phytotoxins
Winn, Michael,Francis, Daniel,Micklefield, Jason
supporting information, p. 6830 - 6833 (2018/06/04)
Thaxtomins are diketopiperazine phytotoxins produced by Streptomyces scabies and other actinobacterial plant pathogens that inhibit cellulose biosynthesis in plants. Due to their potent bioactivity and novel mode of action there has been considerable interest in developing thaxtomins as herbicides for crop protection. To address the need for more stable derivatives, we have developed a new approach for structural diversification of thaxtomins. Genes encoding the thaxtomin NRPS from S. scabies, along with genes encoding a promiscuous tryptophan synthase (TrpS) from Salmonella typhimurium, were assembled in a heterologous host Streptomyces albus. Upon feeding indole derivatives to the engineered S. albus strain, tryptophan intermediates with alternative substituents are biosynthesized and incorporated by the NRPS to deliver a series of thaxtomins with different functionalities in place of the nitro group. The approach described herein, demonstrates how genes from different pathways and different bacterial origins can be combined in a heterologous host to create a de novo biosynthetic pathway to “non-natural” product target compounds.
Probing Ergot Alkaloid Biosynthesis: Synthesis and Feeding of a Proposed Intermediate along the Biosynthetic Pathway. A New Amidomalonate for Tryptophan Elaboration
Kozikowski, Alan P.,Okita, Makoto,Kobayashi, Motomasa,Floss, Heinz G.
, p. 863 - 869 (2007/10/02)
The total synthesis of the diastereoisomeric amino acids 2 and their N-trideuteriomethyl analogues has been carried out.These compounds represent possible intermediates along the biosynthetic pathway from 4-(γ,γ-dimethylallyl)tryptophan (1) to the ergot alkaloids (e.g., 3a).The synthetic scheme features the preparation of an (indolylvinyl)metalic reagent from 4-ethynylindole via a hydrostannylation/metal-metal exchange sequence, as well as the preparation of dimethyl amino>malonate, a new amidomalonate reagent for tryptophan elaboration.Incorporation experiments with Claviceps sp.SD58 followed by GC-MS analysis of the major alkaloid, elymoclavine, showed that neither diastereomer of 2-d3 is an ergot alkaloid precursor.
