π-Extension of a 4-ethoxy-1,3-thiazole via aryl alkyne cross coupling: synthesis and exploration of the electronic structure.

A series of four donor aryl alkynyl substituted thiazole derivatives 3a-d and three similar aryl donor-acceptor systems 6a-c have been synthesized. All compounds bear different electron-donating groups in the 5-position of the thiazole core. The influence of both electron donor strength and the additional phenylethynyl unit on photophysical properties, i.e. UV/Vis absorption, fluorescence emission and fluorescence lifetime, has been evaluated. Additionally, theoretical calculations have been performed at the CAM-B3LYP/6-31+G(d,p) level and good agreement with the experimental data has been achieved. The new derivatives synthesized via palladium catalyzed cross coupling are characterised by moderately strong emission between 474 and 538 nm (ΦF = 0.35-0.39) and Stokes' shifts ranging from 0.54 to 0.79 eV (4392-6351 cm(-1)). The smaller chromophores of type 6 exhibit modest to high fluorescence emission (ΦF = 0.45-0.76) between 470 and 529 nm and their Stokes' shifts range from 0.59 to 0.65 eV (4765-5251 cm(-1)).

Molecular, pharmacological, and signaling properties of octopamine receptors from honeybee (Apis mellifera) brain.

G protein-coupled receptors are important regulators of cellular signaling processes. Within the large family of rhodopsin-like receptors, those binding to biogenic amines form a discrete subgroup. Activation of biogenic amine receptors leads to transient changes of intracellular Ca²âº-([Ca²âº](i)) or 3',5'-cyclic adenosine monophosphate ([cAMP](i)) concentrations. Both second messengers modulate cellular signaling processes and thereby contribute to long-lasting behavioral effects in an organism. In vivo pharmacology has helped to reveal the functional effects of different biogenic amines in honeybees. The phenolamine octopamine is an important modulator of behavior. Binding of octopamine to its receptors causes elevation of [Ca²âº](i) or [cAMP](i). To date, only one honeybee octopamine receptor that induces Ca²âº signals has been molecularly and pharmacologically characterized. Here, we examined the pharmacological properties of four additional honeybee octopamine receptors. When heterologously expressed, all receptors induced cAMP production after binding to octopamine with EC50(s) in the nanomolar range. Receptor activity was most efficiently blocked by mianserin, a substance with antidepressant activity in vertebrates. The rank order of inhibitory potency for potential receptor antagonists was very similar on all four honeybee receptors with mianserin >> cyproheptadine > metoclopramide > chlorpromazine > phentolamine. The subroot of octopamine receptors activating adenylyl cyclases is the largest that has so far been characterized in arthropods, and it should now be possible to unravel the contribution of individual receptors to the physiology and behavior of honeybees.