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The syntheses and the spectroscopic properties of the 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BPDIPY) dyes and their derivatives are discussed. The analysis shows that the fluorescence characteristics of these compounds can be easily altered by changing their structures.

The preparation of two water-soluble 'through-bond energy transfer cassettes' (TBET-cassettes) which have good extinction coefficients at the donor part and transfer energy to the acceptor parts with good 'overall quantum yields', is presented. Fluorescence resonance energy transfer from one protein functionalized with an appropriate donor could be applied to excite the TBET-cassettes on different proteins to probe protein-protein interactions under conditions that would not be possible for single-dye acceptor systems.

The application of ratiometric probes that absorb ultraviolet (UV) excitation at a fixed wavelength and emit at two different fluorescence wavelengths in a pH dependent manner is demonstrated. The newly designed energy transfer approach to pH probe facilitate observation of processes within the cell and have significant potential for modifications with other pH sensitive donor to give a spectrum of probes with systematically varied pH response transitions.

Abstract: Fluorescent molecules that emit in the near infrared are potentially useful as probes for biotechnology. A relatively under-explored design for probes of this type are the aza-BODIPY dyes; this study was performed to enhance our understanding of these materials and ways in which they may be used in dye cassette systems. Thus, the aza-BODIPY dyes 1a–g were prepared. An advanced intermediate toward an eighth compound in the series, 6h, was made but it could not be complexed with boron effectively to give 1h. Spectroscopic properties of these compounds were recorded, and correlations between substituent effects, UV absorbance, fluorescence emissions, and quantum yields were made. Compound 1a was coupled with a fluorescein–alkyne derivative to give the energy transfer cassettes 2 and 3. Both these compounds gave poor energy transfer and the possible reasons for this were discussed. [Copyright &y& Elsevier]

Identification of a common Diels-Alder pattern in three classes of bioactive natural products led us to study the synthesis and cycloaddition of a new class of cyclic dienes readily available from β,γ-unsaturated lactams. A practical and readily scalable route to the parent p-methoxybenzyl-protected 6- and 7-membered β,γ-unsaturated lactams was developed. These were readily transformed into the corresponding O-silylated dienes, which were reacted with dimethyl and diethyl fumarate to yield stereoselectively highly functionalized bicyclic adducts. These exhibited unexpected and versatile transformations upon acid hydrolysis depending on the nature of the dienophile substituents and the acid catalyst. All reactions have been performed on multigram quantities. These transformations provide a convenient, economical, and easily scalable pathway for the rapid construction of functionally and stereochemically dense privileged scaffolds for the construction of libraries of natural products-inspired molecules of pharmacological relevance., (© 2020 Wiley-VCH GmbH.)

Four systems 1a - d were prepared to investigate the optical properties of copolymers comprised of polyfluorene doped with BODIPY-based fluors. The underlying hypothesis was energy harvested via the strong absorptivity of the major component, fluorine, would be primarily emitted from the BODIPY parts at much higher wavelengths. Optimization of the polymerization process as a function of the mol % of BODIPY, indicated that the brightest polymers were formed when approximately 4 fluorene units were co-polymerized with every BODIPY precursor. These polymers were cast into nanoparticles of ca 40 nm diameter. Treatment of clone 9 rat liver cells with suspensions of these particles resulted in uptake without encapsulation in lysosomes, or organelle targeting.

(-)-Spongidepsin 1, a cytotoxic marine natural product, was prepared via two iridium-catalyzed hydrogenation reactions; both were highly stereoselective, giving convenient access to pivotal intermediates. This synthesis was modified to give several spongidepsin analogues, and their cytotoxicities were compared with those of the natural product.