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A series of L-phenylalanine ionic liquids (ILs), L-tyrosine ILs, tertiary amino analogues and proposed transformation products (PTPs) have been synthesised. Antimicrobial toxicity data, as part of the green chemistry metrics evaluation and to supplement preliminary biodegradation studies, was determined for ILs, tertiary amino analogues and PTPs. Good to very good overall yields (76 to 87%) for the synthesis of 6 ILs from L-phenylalanine were achieved. A C 2 -symmetric IL was prepared from TMS-imidazole in a one-pot two-step method in excellent yield (91%). Synthesis of the L-tyrosine IL derivatives utilised a simple protection group strategy by using an extra equivalent of the bromoacetyl bromide reagent. Improvements in the synthesis of the α-bromoamide alkylating reagent from L-phenylalanine were achieved, directed by green chemistry metric analysis. A solvent switch from dichloromethane to THF is described, however the yield was 15% lower. Antimicrobial activity testing of L-phenylalanine ILs, L-tyrosine ILs, tertiary amino analogues and PTPs, against 8 bacteria and 12 fungi strains, showed that no compound had a high antimicrobial activity, apart from an L-proline analogue. In this exceptional case, the highest toxicity (IC 95 = 125 and 250 µM) was observed towards the two Gram positive strains Staphylococcus aureus and Staphylococcus epidermidis respectively. High antimicrobial activity was not found for the other bacteria or fungi strains screened. The limitations of the antimicrobial activity study is discussed in relation to SAR studies. Preliminary analysis of biodegradation data (Closed Bottle Test, OECD 301D) is presented. The pyridinium IL derivative is the preferred green IL of the series based on synthesis, toxicity and biodegradation considerations. This work is a joint study with Kümmerer and co-workers and the PTPs were selected as target compounds based on concurrent biodegradation studies by the Kümmerer group. For the comprehensive biodegradation and transformation product analysis see the accompanying paper.

Over the past few decades ionic liquids (ILs) are increasingly seen as an important building block of green chemistry because of their specific properties as solvents, such as their potential for high recyclability, low volatility, low flammability, low toxicity, and their potential for synthesis from renewable resources. However, avoiding persistent or toxic cation/anion fragments is also urgently needed. In the best case they should be fully mineralizable by microorganisms after their release into the aquatic environment. The fragments fostering this can be determined by biodegradation studies, and the employment of identified readily biodegradable building blocks presents an innovation in the targeted design of green environmentally friendly ILs. The aim of this study was to improve the data-platform for the design of completely mineralizable ILs. Therefore the ready biodegradability of seven phenylalanine-based ILs and three nonionic related compounds was investigated with a modified Closed Bottle test based on OECD guideline 301D. Liquid chromatography combined with high-resolution mass spectrometry (LC-HRMS) analysis was used to identify the chemical structures of products resulting from incomplete biodegradation and transformation. Two kinds of degradation pathways were observed: the hydrolysis of an ethyl ester group or the hydrolysis of an amide bond and biodegradation of the released phenylalanine ethyl ester. Both degradation pathways resulted in persistent transformation products (TPs) with the exception of IL (4), a pyridinium substituted phenylalanine derived IL and the non-ionic deanol derivative (2a). IL (4) was ultimately biodegraded in the CBT after 42 days without leaving any TP. The biodegradation of compound (2a) was 78% after 42 days but resulted in a TP, which was readily biodegradable in a further CBT after a lag phase of 3 weeks, respectively. Even if both compounds were not "readily biodegradable" in the sense of the OECD guideline, particularly IL (4) can be proposed as a basic structure for sustainable and green ILs (benign by design) with the aim of optimizing its degradation rate further. † Electronic supplementary information (ESI) available. See

Chiral ionic liquids (CILs) tetrabutylammonium-(S)-prolinate, tetrabutylammonium-(R)-prolinate and tetrabutylammonium trans-4-hydroxy-(S)-prolinate were investigated as chiral additives in the Pdcatalyzed enantioselective hydrogenation of a,b-unsaturated ketones. These CILs were easily prepared in one step from the aminoacid and tetrabutylammonium hydroxide and characterized (NMR, IR, optical rotation, elemental analysis, DSC, viscosity, decomposition temperature). The research strategy was to assess the antimicrobial toxicity (>20 strains) and biodegradability (OECD 301D) of the CILs at the same time as undertaking the asymmetric catalysis study. The Pd-catalyzed enantioselective hydrogenation of the carbon-carbon double bond of a,b-unsaturated ketones under mild conditions (room temperature, 1 atm of H 2 ) in different solvents with CILs present. The best results were obtained in i-PrOH after 18 hours of reaction with a i-PrOH/IL ratio of 5. While all three CILs have low antimicrobial toxicity to a wide range of bacteria and fungi, tetrabutylammonium-(S)-prolinate, tetrabutylammonium-(R)-prolinate and tetrabutylammonium trans-4-hydroxy-(S)-prolinate did not pass the Closed Bottle biodegradation test.