Short Flow-Photochemistry Enabled Synthesis of the Cytotoxic Lactone (+)-Goniofufurone

Continuous-Flow Chemistry and Photochemistry for Manufacturing of Active Pharmaceutical Ingredients

An active pharmaceutical ingredient (API) is any substance in a pharmaceutical product that is biologically active. That means the specific molecular entity is capable of achieving a defined biological effect on the target. These ingredients need to meet very strict limits; chemical and optical purity are considered to be the most important ones. A continuous-flow synthetic methodology which utilizes a continuously flowing stream of reactive fluids can be easily combined with photochemistry, which works with the chemical effects of light. These methods can be useful tools to meet these strict limits. Both of these methods are unique and powerful tools for the preparation of natural products or active pharmaceutical ingredients and their precursors with high structural complexity under mild conditions. This review shows some main directions in the field of active pharmaceutical ingredients' preparation using continuous-flow chemistry and photochemistry with numerous examples of industry and laboratory-scale applications.

Biomimetic total synthesis of plakortone Q via acid-mediated tandem cyclization

Plakortone Q and plakdiepoxide are natural polyketides isolated from the marine sponge Plakortis simplex. Bicyclo[3.3.0]furanolactone compounds, including plakortone Q, are expected to exhibit a wide range of pharmacological activities. Therefore, developing a simple and versatile synthetic method to produce these compounds is an important research goal. We have achieved the first total synthesis of plakortone Q and plakdiepoxide through an efficient protecting-group-free strategy. The key transformation was an acid-mediated tandem 5-endo-tet/5-endo-tet cyclization of vicinal diepoxide to build the tetrahydrofuran-γ-lactone motif.

Technological Innovations in Photochemistry for Organic Synthesis: Flow Chemistry, High-Throughput Experimentation, Scale-up, and Photoelectrochemistry

Photoinduced chemical transformations have received in recent years a tremendous amount of attention, providing a plethora of opportunities to synthetic organic chemists. However, performing a photochemical transformation can be quite a challenge because of various issues related to the delivery of photons. These challenges have barred the widespread adoption of photochemical steps in the chemical industry. However, in the past decade, several technological innovations have led to more reproducible, selective, and scalable photoinduced reactions. Herein, we provide a comprehensive overview of these exciting technological advances, including flow chemistry, high-throughput experimentation, reactor design and scale-up, and the combination of photo- and electro-chemistry.

Synthesis of anti-proliferative [3.3.0]furofuranone derivatives by lactonization and functionalization of C-glycosyl compounds

The [3.3.0]furofuranone structure is found in numerous families of biologically active natural products. We took advantage of the stereodiversity afforded by carbohydrate derivatives to prepare several compounds structurally similar to goniofufurone and crassalactones which are natural cytotoxic agents. We designed and synthesized several stereoisomers of these natural compounds via lactonization of C-glycosyl compounds bearing an hydroxyl on position 4 and a methyl ester on the pseudo-anomeric positionThe reactivity of this bicyclic moiety was explored through etherification of hydroxyls in position 5 and 7 and various substituants (halogen, phenyl, benzyl, cynanmoyl) were introduced. The anti-proliferative properties of these mimics were then evaluated on various cancer cell lines and two compounds 24 and 35 demonstrated IC₅₀ value of 1.34 µM (U251) and 7.60 µM (U87) respectively.

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

Due to their intrinsic physical properties, which includes being able to perform as volatile liquids at room and biological temperatures, fragrance ingredients/intermediates make ideal candidates for continuous-flow manufacturing. This review highlights the potential crossover between a multibillion dollar industry and the flourishing sub-field of flow chemistry evolving within the discipline of organic synthesis. This is illustrated through selected examples of industrially important transformations specific to the fragrances and flavours industry and by highlighting the advantages of conducting these transformations by using a flow approach. This review is designed to be a compendium of techniques and apparatus already published in the chemical and engineering literature which would constitute a known solution or inspiration for commonly encountered procedures in the manufacture of fragrance and flavour chemicals.

Flow Chemistry for Cycloaddition Reactions

Continuous flow reactors form part of a rapidly growing research area that has changed the way synthetic chemistry is performed not only in academia but also at the industrial level. This Review highlights the most recent advances in cycloaddition reactions performed in flow systems. Cycloadditions are atom-efficient transformations for the synthesis of carbo- and heterocycles, involved in the construction of challenging skeletons of complex molecules. The main advantages of translating these processes into flow include using intensified conditions, safer handling of hazardous reagents and gases, easy tuning of reaction conditions, and straightforward scaling up. These benefits are especially important in cycloadditions such as the copper(I)-catalyzed azide alkyne cycloaddition (CuAAC), Diels-Alder reaction, ozonolysis and [2+2] photocycloadditions. Some of these transformations are key reactions in the industrial synthesis of pharmaceuticals.

Continuous Flow Photochemistry for the Preparation of Bioactive Molecules

The last decade has witnessed a remarkable development towards improved and new photochemical transformations in response to greener and more sustainable chemical synthesis needs. Additionally, the availability of modern continuous flow reactors has enabled widespread applications in view of more streamlined and custom designed flow processes. In this focused review article, we wish to evaluate the standing of the field of continuous flow photochemistry with a specific emphasis on the generation of bioactive entities, including natural products, drugs and their precursors. To this end we highlight key developments in this field that have contributed to the progress achieved to date. Dedicated sections present the variety of suitable reactor designs and set-ups available; a short discussion on the relevance of greener and more sustainable approaches; and selected key applications in the area of bioactive structures. A final section outlines remaining challenges and areas that will benefit from further developments in this fast-moving area. It is hoped that this report provides a valuable update on this important field of synthetic chemistry which may fuel developments in the future.

Sensitized [2 + 2] intramolecular photocycloaddition of unsaturated enones using UV LEDs in a continuous flow reactor: kinetic and preparative aspects

A photocatalysed cycloaddition by benzophenone derivatives under flow and UVA LED irradiation is described.

The Paternò–Büchi reaction – a comprehensive review

This review represents the most complete description of the scientific results obtained on a photochemical reaction described 110 years ago by an Italian scientist.

Novel O-methyl goniofufurone and 7-epi-goniofufurone derivatives: synthesis, in vitro cytotoxicity and SAR analysis

Novel goniofufurone (1) and 7-epi-goniofufurone (2) derivatives bearing a methoxy group at the C-5 and/or C-7 positions were prepared and their in vitro antitumour activity against some human tumour cell lines was evaluated. Some of the analogues displayed powerful antiproliferative effects against the studied tumour cells, but almost all of them were non-cytotoxic toward the normal cells (MRC-5). A SAR study reveals that the introduction of a methoxy group at the C-7 position may increase the antiproliferative effects of the analogues. The most active compounds are 7-O-methyl derivatives of goniofufurone (3) and 7-epi-(+)-goniofufurone (6), which exhibited 1177- and 451-fold higher potencies than the leads 1 and 2 toward the MDA-MB 231 cell line. At the same time, compound 3 is almost 1.5-fold more active than the commercial drug doxorubicin (DOX) against the same cell line. Flow cytometry data confirmed that the cytotoxic effects of these analogues are mediated by apoptosis, additionally revealing that these molecules induced changes in the K562 cell cycle distribution.