RESUMO
Strigolactones (SLs) are a family of terpenoid allelochemicals that were recognized as plant hormones only a decade ago. They influence a myriad of both above- and below-ground developmental processes, and are an important survival strategy for plants in nutrient-deprived soils. A rapidly emerging approach to gain knowledge on hormone signaling is the use of traceable analogs. A unique class of labeled SL analogs was constructed, in which the original tricyclic lactone moiety of natural SLs is replaced by a fluorescent cyanoisoindole ring system. Biological evaluation as parasitic seed germination stimulant and hypocotyl elongation repressor proved the potency of the cyanoisoindole strigolactone analogs (CISAs) to be comparable to the commonly accepted standard GR24. Additionally, via a SMXL6 protein degradation assay, we provided molecular evidence that the compounds elicit SL-like responses through the natural signaling cascade. All CISAs were shown to exhibit fluorescent properties, and the high quantum yield and Stokes shift of the pyrroloindole derivative CISA-7 also enabled in vivo visualization in plants. In contrast to the previously reported fluorescent analogs, CISA-7 displays a large similarity in shape and structure with natural SLs, which renders the analog a promising tracer to investigate the spatiotemporal distribution of SLs in plants and fungi.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Lactonas/química , Proteólise , Transdução de Sinais , Arabidopsis/fisiologia , Proteínas de Arabidopsis/genética , Corantes Fluorescentes , Germinação , Hipocótilo/genética , Hipocótilo/fisiologia , Reguladores de Crescimento de Plantas/metabolismo , Sementes/genética , Sementes/fisiologiaRESUMO
Bromination reactions are crucial in today's chemical industry since the versatility of the formed organobromides makes them suitable building blocks for numerous syntheses. However, the use of the toxic and highly reactive molecular bromine (Br2) makes these brominations very challenging and hazardous. We describe here a safe and straightforward protocol for bromination in continuous flow. The hazardous Br2 or KOBr is generated in situ by reacting an oxidant (NaOCl) with HBr or KBr, respectively, which is directly coupled to the bromination reaction and a quench of residual bromine. This protocol was demonstrated by polybrominating both alkenes and aromatic substrates in a wide variety of solvents, with yields ranging from 78% to 99%. The protocol can easily be adapted for the bromination of other substrates in an academic and industrial environment.
Assuntos
Bromo/química , Fenômenos de Química Orgânica , Concentração de Íons de Hidrogênio , Líquidos Iônicos/síntese química , Líquidos Iônicos/química , Espectroscopia de Ressonância Magnética , Estrutura MolecularRESUMO
3-Chloropropionyl chloride is a chemically versatile building block with applications in the field of adhesives, pharmaceuticals, herbicides and fungicides. Its current production entails problems concerning safety, prolonged reaction times and the use of excessive amounts of chlorinating reagents. We developed a continuous flow procedure for acid chloride formation from acrylic acid and a consecutive 1,4-addition of hydrogen chloride generating 3-chloropropionyl chloride, as presented in this paper. Up to 94 % conversion was reached in 25â minutes at mild temperatures and pressures. This continuous flow method offers a safer alternative and is highly efficient in terms of consumption of starting product and shorter residence time. Valorization of this building block is exemplified by the synthesis of beclamide, a compound with sedative and anticonvulsant properties. Over 80 % conversion towards this drug was achieved in 1â minute in a continuous flow setup. Further research is needed to telescope the synthesis of 3-chloropropionyl chloride and subsequent beclamide formation without intermediate purification.
RESUMO
This review summarizes recent literature (2000-2015) on the synthesis and pharmaceutical properties of pyrrolopyrimidines. These modified pyrimidine bases, fused to a pyrrole ring, and their corresponding nucleosides display a broad applicability in medicinal chemistry. This overview is divided into three main sections, according to the respective isomers: pyrrolo[2,3-d]pyrimidines, pyrrolo[3,2-d]pyrimidines, and pyrrolo[3,4-d]pyrimidines. Each section contains a description of common retro-synthetic strategies, with particular attention for newly reported synthetic entries to the scaffold. Next, the synthetic strategies and the ways in which the scaffolds can be further modified are exemplified according to the biological properties of the obtained products.
Assuntos
Técnicas de Química Sintética/métodos , Descoberta de Drogas , Pirimidinas/síntese química , Pirimidinas/farmacologia , Pirróis/síntese química , Pirróis/farmacologia , Animais , Descoberta de Drogas/métodos , Humanos , Modelos Moleculares , Pirimidinas/química , Pirróis/químicaRESUMO
The first synthesis of benzoxaphospholenes dates back to the 1960s. Since then, the structural variety of reported (benz)oxaphospholenes has steadily increased. Organophosphorus compounds have caught the interest of synthetic chemists for a couple of decades now because of their interesting biological properties. Oxaphospholenes, in particular, could serve as carbohydrate mimetics, and benzoxaphospholenes have been reported to possess bactericidal, insecticidal, herbicidal, and fungistatical properties. Transesterification reactions and addition of phosphorus nucleophiles to carbonyl compounds were reaction types that led to the production of the first (benz)oxaphospholenes. When it was discovered that allenylphosphonates could easily be obtained from propargyl alcohols and dialkyl halophosphites, the electrophile-induced cyclization reaction of these allenylphosphonate precursors resulted in a huge boom in the amount of reports on oxaphospholene synthesis. To this day, this method is still frequently used. Ring-closing metathesis and Horner-Wadsworth-Emmons reactions have also proven their potential for the preparation of oxaphospholenes. In recent years, Pd, Rh and Au-catalysis have made their entry, generating (benz)oxaphospholenes from a wide variety of simple substrates. A couple of miscellaneous methods are summarized at the end of the Review.
RESUMO
The addition of phosphite nucleophiles across linear unsaturated imines is a powerful and atom-economical methodology for the synthesis of aminophosphonates. These products are of interest from both a biological and a synthetic point of view: they act as amino acid transition state analogs and Horner-Wadsworth-Emmons reagents, respectively. In this work the reaction between dialkyl trimethylsilyl phosphites and α,ß,γ,δ-diunsaturated imines was evaluated as a continuation of our previous efforts in the field. As such, the first conjugate 1,6-addition of a phosphite nucleophile across a linear unsaturated N-containing system is reported herein. Theoretical calculations were performed to rationalize the observed regioselectivites and to shed light on the proposed mechanism.
RESUMO
Phosphonylated pyrroles were obtained by a ZnCl2-catalyzed 5-exo-dig hydroamination of propargylic enamines. These starting compounds were obtained in two steps from commercially available ß-ketophosphonates. The method tolerates a wide variety of substituents at the 1,2- and 5-position of the pyrrole, while further derivatization allows for the introduction of substituents at the 4-position via lithiation or halogenation.
Assuntos
Compostos Organofosforados/química , Compostos Organofosforados/síntese química , Pirróis/química , Pirróis/síntese química , Aminação , Catálise , Ciclização , Halogenação , Estrutura MolecularRESUMO
3-Azabicyclo[3.1.0]hex-2-en-1-yl phosphonates were prepared in a five-step reaction route from ß-ketophosphonates. The key steps in this sequence are an atom-transfer radical cyclization and an unforeseen lithium-halogen exchange with n-BuLi. The cyclization reaction proceeds with excellent diastereoselectivity. The resulting cyclic imines were reduced, and 3-azabicyclo[3.1.0]hexan-1-yl phosphonates were obtained.
Assuntos
Compostos Azabicíclicos/síntese química , Organofosfonatos/química , Ácidos Fosforosos/síntese química , Compostos Azabicíclicos/química , Ciclização , Estrutura Molecular , Ácidos Fosforosos/química , EstereoisomerismoRESUMO
Over the past few years, isoindoles have found wide application in materials science. Isoindole containing BODIPY dyes are highly fluorescent materials and have been extensively used in various fields of science. Phthalocyanines, metal containing cyclic tetramers of isoindole, form coordination complexes with most elements of the periodic table. These complexes are intensely coloured and are used as pigments and dyes. However, isoindoles are relatively unstable 10π-heteroaromatic systems and few synthetic methods provide these compounds in good yields. This tutorial review will give an overview of the reported synthetic methods towards isoindoles and related heteroaromatic systems over a time span of approximately 10 years (2000 to current), including the applications where they have been reported. The importance of the field will be illustrated and factors influencing product stability will be discussed.
Assuntos
Técnicas de Química Sintética/métodos , Isoindóis/síntese química , Pirróis/síntese química , Pirróis/químicaRESUMO
A two step synthesis of dihydrothiazoles is presented. First, the previously unknown N-propargylic dithiocarboimidates are produced in good yields from easily available, cheap starting materials. The subsequent gold catalysed ring closure is fast and efficient, leading to dihydrothiazoles through a cascade of 5-exo-dig cyclisation and 1,3-alkyl migration. The yields range from 74% to 95%.
Assuntos
Compostos de Ouro/química , Tiazóis/síntese química , Alquilação , Catálise , Hidrogenação , Estrutura MolecularRESUMO
The unique nucleophilic properties of lithiated methoxyallene allow for C-C bond formation with a wide variety of electrophiles, thus introducing an allenic group for further functionalization. This approach has yielded a tremendously broad range of (hetero)cyclic scaffolds, including precursors to active pharmaceutical ingredients. To date, however, its valorization at scale is hampered by the batch synthesis procedure, which suffers from serious safety issues. Hence, the attractive heat- and mass-transfer properties of flow technology were exploited to establish a mesoscale continuous-flow route toward lithiated methoxyallene. An excellent conversion of 94 % was obtained, corresponding to a methoxyallene throughput of 8.2â g h-1 . The process is characterized by short reaction times, mild reaction conditions and a stoichiometric use of reagents.
RESUMO
Acid chlorides are an important class of compounds and their high reactivity and instability has prompted us to develop a straightforward procedure for their synthesis with on-demand and on-site synthesis possibilities. The focus of this report is acryloyl chloride, mainly important for the acrylate and polymer industry. A continuous-flow methodology was developed for the fast and selective synthesis of the otherwise highly unstable acryloyl chloride. Three routes were investigated in a microreactor setup and all three can potentially be used for its production. The methodology was further expanded to the synthesis of other unstable acid chlorides by both the thionyl chloride and the oxalyl chloride mediated processes. The most sustainable method was the oxalyl chloride mediated procedure under solvent-free conditions, in which near-equimolar amounts of carboxylic acid and oxalyl chloride were used in the presence of catalytic amounts of DMF at room temperature. Within 1 to 3â min, nearly full conversions into the acid chlorides were achieved.
Assuntos
Acrilatos/síntese química , Química Verde/métodos , Segurança , Técnicas de Química Sintética , Solventes/químicaRESUMO
3-Imidoallenylphosphonates, allenes bearing both an electron-withdrawing and -donating group, were isolated for the first time. An alkoxy substituent was introduced into these unprecedented intermediates in a one-pot approach, yielding ß-functionalized aminophosphonates in excellent yields and short reaction times. The mechanistic insights gained are important additions to the domain of allene chemistry. Addition of biologically important molecules, including monoglycerides, amino acids, and nucleosides, proves the general applicability of the developed method.
Assuntos
Organofosfonatos/química , Álcoois/química , Alcadienos/química , Aminoácidos/química , Catálise , Ciclopropanos/química , Estrutura Molecular , Nucleosídeos/química , EstereoisomerismoRESUMO
Singlet-oxygen oxidation of 5-hydroxymethylfurfural (5-HMF) was performed in continuous flow mode using rose Bengal as photosensitizer. The resulting butenolide (H(2) MF) was formed selectively in high yield. The procedure proved to be scalable and applicable to related bio-based furfurals. Furthermore, preliminary data show that H(2) MF can be readily isomerized thermally to 5-hydroxy-4-keto-pentenoic acid oligomers.
Assuntos
Furaldeído/análogos & derivados , Oxigênio Singlete/química , 4-Butirolactona/análogos & derivados , 4-Butirolactona/química , Furaldeído/química , Luz , Oxirredução , Fármacos Fotossensibilizantes/química , Rosa Bengala/químicaRESUMO
A three-step synthesis of benzo[c]thiophenes is presented in which the key transformation is the gold-catalyzed 5-exo-dig migratory cycloisomerization of a diallyl thioacetal. It was shown that a small amount of in situ generated HAuCl4 from AuCl3 is the active catalytic species. A mechanism was proposed.
Assuntos
Derivados de Benzeno/síntese química , Cloretos/química , Compostos de Ouro/química , Tiofenos/síntese química , Derivados de Benzeno/química , Catálise , Ciclização , Isomerismo , Tiofenos/químicaRESUMO
Strigolactones (SLs) are known not only as plant hormones, but also as rhizosphere signals for establishing symbiotic and parasitic interactions. The design of new specific SL analogs is a challenging goal in understanding the basic plant biology and is also useful to control plant architectures without favoring the development of parasitic plants. Two different molecules (23 (3'-methyl-GR24), 31 (thia-3'-methyl-debranone-like molecule)) already described, and a new one (AR36), for which the synthesis is presented, are biologically compared with the well-known GR24 and the recently identified CISA-1. These different structures emphasize the wide range of parts attached to the D-ring for the bioactivity as a plant hormone. These new compounds possess a common dimethylbutenolide motif but their structure varies in the ABC part of the molecules: 23 has the same ABC part as GR24, while 31 and AR36 carry, respectively, an aromatic ring and an acyclic carbon chain. Detailed information is given for the bioactivity of such derivatives in strigolactone synthesis or in perception mutant plants (pea rms1 and rms4, Arabidopsis max2 and, max4) for different hormonal functions along with their action in the rhizosphere on arbuscular mycorrhizal hyphal growth and parasitic weed germination.
Assuntos
Lactonas/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Rizosfera , Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , Glomeromycota/metabolismoRESUMO
A two-step synthesis of 1-cyanoisoindoles starting from ethynylbenzaldehyde is presented. The key step is a mild, high-yielding, gold-catalyzed rearrangement of N-allylic aminonitriles.