Photodynamic inactivation of bacteria (PIB) by efficient singlet oxygen photosensitizers might be a beneficial alternative to antibiotics in the struggle against multiresistant bacteria. Phenothiazinium dyes belong to the most prominent classes of such sensitizers due to their intense absorption in the red-light region (λ abs, max ca. 600–680 nm, ε > 50000 L mol−1 cm−1), their low toxicity, and their attachment/penetration abilities. Except simple substituents like alkyl or hydroxyalkyl residues, nearly no modifications of the phenothiaziniums have been pursued at the auxochromic sites. By this, the properties of methylene blue derivatives and their fields of application are limited; it remains unclear if their potential antimicrobial efficacy may be enhanced, also to compete with porphyrins. We prepared a set of six mainly novel methylene blue derivatives with the ability of additional hydrogen bonding and/or additional cationic charges to study the substituents' effect on their activity/toxicity profiles and photophysical properties. Direct detection of singlet oxygen was performed at 1270 nm and the singlet oxygen quantum yields were determined. In suspensions with both, Gram-positive and Gram-negative bacteria, some derivatives were highly active upon illumination to inactivate S. aureus and E. coli up to 7 log10 steps (99.99999%) without inherent toxicities in the nonirradiated state.

In memory of Klaus HafnerThe 2-pyrone moiety can be found in a large number of natural products with a wide range of biological activities, including antibiotic, antifungal, cytotoxic, neurotoxic, phytotoxic, antiinflammatory and cardiotonic effects. With its heterocyclic structure encompassing the chemical nature of conjugated dienes, lactones, Michael acceptors and arenes, it can undergo a great variety of transformations such as cycloadditions, ringopening reactions, cross-couplings and lactamizations. Thus, 2-pyrones represent valuable synthetic precursors and worthwhile targets in organic, polymer, and medical chemistry. Owing to its exquisite chemical and physical properties, the synthesis and further transformations of 2-pyrones have attracted considerable attention over the past decade, showcasing transition metal and metal free strategies and using readily available starting materials, notably those stemming from renewable resources.

Male euglossine bees exhibit unique adaptations for the acquisition and accumulation of chemical compounds from “perfume flowers” and other sources. During courtship display, male bees expose perfume mixtures, presumably to convey species-specific recognition and/or mate choice signals to females. Because olfaction regulates both signal production (in males) and signal detection (in females) in this communication system, strong selective pressures are expected to act on the olfactory system, which could lead to sensory specialization in favor of an increased sensitivity to specific chemical compounds. The floral scents of euglossine-pollinated plants are hypothesized to have evolved in response to the preexisting sensory biases of their male euglossine bee pollinators. However, this has never been investigated at the peripheral olfactory circuitry of distinct pollinating genera. Here, we present a comparative analysis using electroantennography (EAG) of males across the phylogeny of 29 euglossine bee species, among them Euglossa and Eulaema species. First, we tested whether antennal responses differ among different euglossine genera, subgenera and species. Secondly, we conducted a comparative phylogenetic analysis to investigate the macroevolutionary patterns of antennal responses across the euglossine bee phylogeny. We found that antennal response profiles are very unique on the species level and differ on the subgenus and the genus level. The differences can be explained by chemical compounds typically found in the floral scent bouquets of perfume flowers and specific compounds of species either pollinated by Euglossa (e.g., ipsdienol) or Eulaema bees (e.g., (−)-(E)-carvone epoxide). Also, we detected a phylogenetic signal in mean antennal responses and found that especially at the species level of our simulation the overall antennal responses exhibit greater disparity relative to a null model of pure Brownian-motion across the phylogeny. Altogether, our results suggest that (1) euglossine bee species exhibit species-specific antennal responses that differ among euglossine genera and subgenera, (2) antennal responses diverge early after speciation events, and (3) scent composition of perfume flowers evolved in response to pollinator-mediated selection imposed by preexisting sensory biases in euglossine bees.

No abstract

An atom-economic reaction sequence to 6-substituted 2-pyrones was developed starting from furfuryl alcohol, a renewable resource made from bran or bagasse, and aldehydes, utilizing a thermal rearrangement of cyclopentadienone epoxides as key step. Derivatives bearing a hydroxyalkyl side chain could be enzymatically resolved, providing access to enantiomerically pure 2-pyrones, or converted to alkenyl-substituted 2-pyrones such as naturally occurring sibirinone, (E)-6-(pent-1-en-1-yl)-2H-pyran-2-one, and (E)-6-(hept-1-en-1-yl)-2H-pyran-2-one.