Osmoregulation in phytoplankton is attributed to several highly polar low-molecular-weight metabolites. A widely accepted model considers dimethylsulfoniopropionate (DMSP) as the most important and abundant osmotically active metabolite. Using an optimized procedure for the extraction and detection of highly polar metabolites, we expand the group of phytoplankton osmolytes by identifying ectoine in several microalgae. Ectoine is known as a bacterial compatible solute, but, to the best of our knowledge, was never considered as a phytoplankton-derived product. Given the ability of microalgae to take up zwitterions, such as DMSP, we tested the hypothesis that the algal ectoine is derived from associated bacteria. We therefore analyzed methanol extracts of xenic and axenic cultures of two different species of microalgae and could detect elevated concentrations of ectoine in those that harbor associated bacteria. However, also microalgae without an associated microbiome contain ectoine in smaller amounts, pointing towards a dual origin of this metabolite in the algae from their own biosynthesis as well as from uptake. We also tested the role of ectoine in the osmoadaptation of microalgae. In the model diatoms Thalassiosira weissflogii and Phaeodactylum tricornutum, elevated amounts of ectoine were found when cultivated in seawater with salinities of 50 PSU compared to the standard culture conditions of 35 PSU. Therefore, we add ectoine to the family of osmoadaptive metabolites in phytoplankton and prove a new, potentially synergistic metabolic interplay of bacteria and algae.

The direct synthesis of organocalcium compounds (heavy Grignard reagents) by the reduction of organyl halides with activated calcium powder succeeded in a straightforward manner for organic bromides and iodides that are bound at sp -hybridized carbon atoms. Extension of this strategy to alkyl halides was very limited, and only the reduction of trialkylsilylmethyl bromides and iodides with activated calcium allowed the isolation of the corresponding heavy Grignard reagents. Substitution of only one hydrogen atom of the methylene moiety by a phenyl or methyl group directed this reduction toward the Wurtz-type coupling and the formation of calcium halide and the corresponding C-C coupling product. The stability of the methylcalcium and benzylcalcium derivatives in ethereal solvents suggests an unexpected reaction behavior of the intermediate organyl halide radical anions. Quantum chemical calculations verify a dependency between the ease of preparative access to organocalcium complexes and the C-I bond lengths of the organyl iodides. The bulkiness of the trialkylsilyl group is of minor importance. Chloromethyltrimethylsilane did not react with activated calcium; however, halogen-exchange reactions allowed the isolation of [Ca(CH SiMe )(thf) (μ-Cl)] . Furthermore, the metathetical approach of reacting [Ca(CH SiMe )I(thf) ] with KN(SiMe ) and the addition of N,N,N',N'',N''-pentamethyldiethylenetriamine (pmdeta) allowed the isolation of heteroleptic [CaCH SiMe {N(SiMe ) }(pmdeta)]. In the reaction of this derivative with phenylsilane, the trimethylsilylmethyl group proved to be more reactive than the bis(trimethylsilyl)amido substituent.

Hydrocarbon-soluble and highly reactive [(L) x Ca(CH 2 SiMe 3 ) 2 ] (L = tetrahydropyran, x = 4 (2a); L = tmeda, x = 2 (2b)) is synthesized by the metathesis reaction of Me 3 SiCH 2 CaI (1-I) with KCH 2 SiMe 3 . The durability of 2a in tetrahydropyran solution at 0 °C is sufficiently high for subsequent chemical transformations. The reaction of ICH 2 SiMe 3 with calcium in diethyl ether yields unique cage compound 3). We demonstrate that alkylcalcium complexes are valuable reagents for calcium−iodine exchange reactions at C sp 2 −I functionalities.

A microalga produces the toxic halogenated anilines 2,4,6-tribromoaniline, 2,4,6-trichloroaniline and their dibromochloro and bromodichloro derivatives that were considered as compounds of exclusive synthetic origin.