The antiinflammatory drug halipeptin A (1) is a 17‐membered cyclic depsipeptide made up of L‐alanine, α‐methylcysteine, decanoic acid, and isoleucine residues. Key steps in its total synthesis, which helped to confirm the stereochemistry of the natural product, include a borane‐mediated aldol reaction and an asymmetric aza‐Claisen rearrangement.

Excessive use of antibiotics in aquaculture severely endangers human health and ecosystems, which has raised significant concerns in recent years. However, conventional laboratory-based approaches regularly required time or skilled manpower. Herein, we propose a point-of-care-testing (POCT) biosensor detection device for the simultaneous determination of multiantibiotics without complex equipment or professional operators. A laser-printed paper-based microfluidic chip loaded with multicolor fluorescence nanoprobes (mCD-μPAD) was developed to rapidly detect sulfamethazine (SMZ), oxytetracycline (OTC), and chloramphenicol (CAP) on-site. These “fluorescence off” detection probes composed of carbon dots (CDs) conjugated with aptamers (donor) and MoS2 nanosheets (acceptor) (CD-apt-MoS2) were based on Förster resonance energy transfer. Upon the addition of target antibiotics, the significantly recovered fluorescence signal on the μPAD can be sensitively perceived by employing a 3D-printed portable detection box through a smartphone. Under optimal conditions, this μPAD allowed for a rapid response of 15 min toward SMZ, OTC, and CAP with considerable sensitivities of 0.47, 0.48, and 0.34 ng/mL, respectively. In shrimp samples, the recoveries were 95.2–101.2, 96.4–105, and 96.7–106.1% with RSD below 6%. This paper-based sensor opens an avenue for on-site, high-throughput, and rapid detection methods and can be widely used in POCT in food safety.

Fluorescent dyes are extensively utilized in various fluorescence imaging techniques. However, many existing modification strategies could not balance the performance (such as brightness, photostability, water solubility, and permeability) of fluorophores. Herein we report a general strategy to enhance the performance of donor–acceptor-type fluorophores by introducing azetidine-containing heterospirocycles to the commonly used fluorophore scaffolds. Such a strategy turned out to be a general way to develop high-quality fluorophores.

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