N-Butylpyrrolidinone is an equally good solvent as N,N-dimethylformamide for microwave assisted solid phase peptide synthesis.

Solid-phase peptide synthesis (SPPS) is the prevailing method for synthesizing research peptides today. However, SPPS is associated with a significant environmental concern due to the utilization of hazardous solvents such as N,N-dimethylformamide (DMF) or N-methylpyrrolidone, which generate substantial waste. In light of this, our research endeavors to identify more environmentally friendly solvents for SPPS. In this study, we have assessed the suitability of five green solvents as alternatives to DMF in microwave assisted SPPS. The solvents evaluated include Cyrene, ethyl acetate, 1,3-dioxolane, tetrahydro-2-methylfuran, and N-Butylpyrrolidinone (NBP). Our investigation encompassed all stages of the synthesis process, from resin swelling, dissolution of reagents, culminating in the successful synthesis of five diverse peptides, including the challenging ACP 65-74, Peptide 18A, Thymosin α1, and Jung-Redemann peptide. Our findings indicate that NBP emerged as a strong contender, performing on par with DMF in all tested syntheses. Furthermore, we observed that combinations of NBP with either ethyl acetate or tetrahydro-2-methylfuran demonstrated excellent results. This research contributes to the pursuit of more sustainable and environmentally conscious practices in peptide synthesis.

Forty Years after the Discovery of Its Nucleolytic Activity: [Cu(phen)2 ]2+ Shows Unattended DNA Cleavage Activity upon Fluorination.

[Cu(phen)2 ]2+ (phen=1,10-phenanthroline) is the first and still one of the most efficient artificial nucleases. In general, when the phen ligand is modified, the nucleolytic activity of its CuII complex is significantly reduced. This is most likely due to higher steric bulk of such ligands and thus lower affinity to DNA. CuII complexes with phen ligands having fluorinated substituents (F, CF3 , SF5 , SCF3 ) surprisingly showed excellent DNA cleavage activity-in contrast to the unsubstituted [Cu(phen)2 ]2+ -in the absence of the otherwise required classical, bioabundant external reducing agents like thiols or ascorbate. This nucleolytic activity correlates well with the half-wave potentials E1/2 of the complexes. Cancer cell studies show cytotoxic effects of all complexes with fluorinated ligands in the low µm range, whereas they were less toxic towards healthy cells (fibroblasts).

Mesityltellurenyl cations stabilized by triphenylpnictogens [MesTe(EPh(3))](+) (E = P, As, Sb).

The homoleptic 1:1 Lewis pair (LP) complex [MesTe(TeMes2)]O3SCF3 (1) featuring the cation [MesTe(TeMes2)](+) (1a) was obtained by the reaction of Mes2Te with HO3SCF3. The reaction of 1 with Ph3E (E = P, As, Sb, Bi) proceeded with substitution of Mes2Te and provided the heteroleptic 1:1 LP complexes [MesTe(EPh3)]O3SCF3 (2, E = P; 3, E = As) and [MesTe(SbPh3)][Ph2Sb(O3SCF3)2] (4) featuring the cations [MesTe(EPh3)](+) (2a, E = P; 3a, E = As; 4a, E = Sb) and the anion [Ph2Sb(O3SCF3)2](-) (4b). In the reaction with Ph3Bi, the crude product contained the cation [MesTe(BiPh3)](+) (5a) and the anion [Ph2Bi(O3SCF3)2](-) (5b); however, the heteroleptic 1:1 LP complex [MesTe(BiPh3)][Ph2Bi(O3SCF3)2] (5) could not be isolated because of its limited stability. Instead, fractional crystallization furnished a large amount of Ph2BiO3SCF3 (6), which was also obtained by the reaction of Ph3Bi with HO3SCF3. The formation of the anions 4b and 5b involves a phenyl group migration from Ph3E (E = Sb, Bi) to the MesTe(+) cation and afforded MesTePh as the byproduct, which was identified in the mother liquor. The heteroleptic 1:1 LP complexes 2-4 were also obtained by the one-pot reaction of Mes2Te, Ph3E (E = P, As, Sb) and HO3SCF3. Compounds 1-4 and 6 were investigated by single-crystal X-ray diffraction. The molecular structures of 1a-4a were used for density functional theory calculations at the B3PW91/TZ level of theory and studied using natural bond order (NBO) analyses as well as real-space bonding descriptors derived from an atoms-in-molecules (AIM) analysis of the theoretically obtained electron density. Additionally, the electron localizability indicator (ELI-D) and the delocalization index are derived from the corresponding pair density.