We describe rhenium(I) triscarbonyl compounds (3 and 4) decorated with simple-to-use 2-iminomethyl-pyridine (1, impy) and 2-aminomethyl-pyridine (2, ampy) ligands, respectively, which can serve as cooperative ligand scaffolds enabling CO 2 binding via a formal [1,3] addition under Re−O and C−C bond formation. fac-[Re(impy)-(CO) 3 Br] (3) is readily prepared by stirring (1-(pyridin-2yl)-N-(p-tolyl)methanimine (impy, 1) and [Re(CO ) 5 Br] in refluxing THF. Alternatively, complex 3 can be readily obtained when a mixture of [Re(CO) 5 Br], p-toluidine, and picolinaldehyde is refluxed in ethanol. Complex 3 is reduced with excess potassium metal in THF (two-electron reduction) to give the anionic amido complex K[Re(amidopy*)(CO) 3 ] (5b, the asterisk indicates the dearomatized ligand). Analysis of the 1 H and 13 C{ 1 H} NMR spectra of 5b suggest the dearomatization of the pyridine unit. Complex 5b is highly reactive and gives rise to the facile [1,3] addition of CO 2 . The addition of the CO 2 and thus the formation of K[Re(amidopy-COO)(CO) 3 ] ( 6) is characterized by the concomitant formation of a Re−O and a C−C bond. The addition is triggered by the rearomatization of the pyridine unit in 6. Remarkably, isotopic labeling experiments involving 13 CO 2 suggest a reversible binding of CO 2 to the complex. The related amine complex fac-[Re(ampy)(CO) 3 Br] (4) is similarly prepared by stirring (4-methyl-N-(pyridin-2ylmethyl)aniline ( 2) and [Re(CO) 5 Br] in THF at 60 °C. Upon addition of excess base (LiHMDS), complex 3 is readily deprotonated twice to give likewise the anionic amido complex Li[Re(amidopy*)(CO) 3 ] (5a). The latter reaction gives rise to a facile access to the reactive dearomatized anionic fragment [Re(amidopy*)(CO) 3 ] − with no need for the application of strong reducing agents. The ion pair M + /[Re(amidopy*)(CO) 3 ] − is highly reactive and combines MLC (metal−ligand cooperation) via a dearomatization/rearomatization scheme and bifunctional reactivity enabled by the nucleophilic nature of the Re complex and the Lewis acidic counter alkali cation.

Proteins are composed of l‐amino acids, but nucleic acids and most oligosaccharides contain d‐sugars as building blocks. It is interesting to ask whether this is a coincidence or a consequence of the functional interplay of these biomolecules. One reaction that provides an opportunity to study this interplay is the formation of phosphoramidate‐linked peptido RNA from amino acids and ribonucleotides in aqueous condensation buffer. Here we report how the diastereoselectivity of the first peptide coupling of the peptido RNA pathway can be determined in situ by NMR spectroscopy. When a racemic mixture of an amino acid ester was allowed to react with an 5′‐aminoacidyl nucleotide, diastereomeric ratios of up to 72 : 28 of the resulting dipeptido nucleotides were found by integration of 31P‐ or 1H‐NMR peaks. The highest diastereomeric excess was found for the homochiral coupling product d‐Ser‐d‐Trp, phosphoramidate‐linked to adenosine 5′‐monophosphate with its d‐ribose ring. When control reactions with an N‐acetyl amino acid and valine methyl ester were run in organic solvent, the diastereoselectivity was found to be lower, with diastereomeric ratios≤62 : 38. The results from the exploratory study thus indicate that the ribonucleotide residue not only facilitates the coupling of lipophilic amino acids in aqueous medium but also the formation of a homochiral dipeptide. The methodology described here may be used to search for other stereoselective reactions that shed light on the origin of homochirality.

The phase sensitive two-dimensional ( 2~) 1 3 c -'~ heteronuclear correlated and double quantum filtered cosy n.m.r. spectra of the triterpenes 7p-acetoxyhopan-22-01 and 2a,38,22atriacetoxystictane have been recorded at a resolution sufficient for the complete assignment of their proton resonances. Revisions to some of the methylene proton resonances of 78-acetoxyhopan-22-01 proposed elsewhere are discussed, and assignments for a series of flavicene and stictane triterpenes are presented. 21, n.m.r. analyses of a new triterpene isolated from the extracts of the lichen Pseudocyphellaria coronata revealed it to be 22a-hydroxystictano-25,3!34actone.

The COVID-19 pandemic puts significant stress on the viral testing capabilities of many countries. Rapid point-of-care (PoC) antigen tests are valuable tools but implementing frequent large scale testing is costly. We have developed an inexpensive device for pooling swabs, extracting specimens, and detecting viral antigens with a commercial lateral flow test for the nucleocapsid protein of SARS-CoV-2 as antigen. The holder of the device can be produced locally through 3D printing. The extraction and the elution can be performed with the entire set-up encapsulated in a transparent bag, minimizing the risk of infection for the operator. With 0.35 mL extraction buffer and six swabs, including a positive control swab, 43 ± 6% (n = 8) of the signal for an individual extraction of a positive control standard was obtained. Image analysis still showed a signal-to-noise ratio of approximately 2:1 at 32-fold dilution of the extract from a single positive control swab. The relative signal from the test line versus the control line was found to scale linearly upon dilution (R2 = 0.98), indicating that other pooling regimes are conceivable. A pilot project involving 14 participants and 18 pooled tests in a laboratory course at our university did not give any false positives, and an individual case study confirmed the ability to detect a SARS-CoV-2 infection with five-fold or six-fold pooling, including one swab from a PCR-confirmed COVID patient. These findings suggest that pooling can make frequent testing more affordable for schools, universities, and similar institutions, without decreasing sensitivity to an unacceptable level.

Dedicated to Ulf DiederichsenPeptidoyl RNAs are the products of ribosome-free, singlenucleotide translation. They contain a peptide in the backbone of the oligoribonucleotide and are interesting from a synthetic and a bioorganic point of view. A synthesis of a stabilized version of peptidoyl RNA, with an amide bond between the Cterminus of a peptide and a 3'-amino-2',3'-dideoxynucleoside in the RNA chain was developed. The preferred synthetic route used an N-Teoc-protected aminonucleoside support and in-volved a solution-phase coupling of the amino-terminal oligonucleotide to a dipeptido dinucleotide. Exploratory UVmelting and NMR analysis of the hairpin 5'-UUGGCGAAAGCdC-LeuLeu-AA-3' indicated that the peptide-linked RNA segments do not fold in a cooperative fashion. The synthetic access to doubly RNA-linked peptides on a scale sufficient for structural biology opens the door to the exploration of their structural and biochemical properties.