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Molecular docking has traditionally mostly been employed in the field of protein- ligand binding. Here, we extend this method, in combination with DFT-level geometry optimizations, to locate guest molecules inside the pores of metal-organic frameworks. The position and nature of the guest molecules tune the physicochemical properties of the host-guest systems. Therefore, it is essential to be able to reliably locate them to rationally enhance the performance of the known metal-organic frameworks and facilitate new material discovery. The results obtained with this approach are compared to experimental data. We show that the presented method can, in general, accurately locate adsorption sites and structures of the host-guest complexes. We therefore propose our approach as a computational alternative when no experimental structures of guest-loaded MOFs are available. Additional information on the adsorption strength in the studied host-guest systems emerges from the computed interaction energies. Our findings provide the basis for other computational studies on MOF-guest systems and contribute to a better understanding of the structure-interaction-property interplay associated with them.

Angewandte Chemie / International edition 62(7), e202211167 (2023). doi:10.1002/anie.202211167, Published by Wiley-VCH, Weinheim

The stereoselectivity and stereospecificity of the triflate‐mediated intramolecular Schmidt reaction of substituted 3‐(1‐azidocyclohexyl)propanol derivatives leading to octahydro‐1H‐pyrrolo[1,2‐a]azepine, the structural skeleton of several important families of alkaloids such as the Stemona alkaloids, has been examined. The reaction involves an initial intramolecular SN2 reaction between the azide moiety and the triflate affording an intermediate spirocyclic aminodiazonoium salt that undergoes the expected 1,2‐shift/N2‐elimination followed by hydride‐mediated iminium salt reduction. Remarkably, chiral alcohols are converted to the azabicyclic derivative with no or limited racemization. The initial asymmetric alcohol center controls the diastereoselectivity of the whole process, leading to the formation of one out of the four possible diastereoisomers of disubstituted octahydro‐1H‐pyrrolo[1,2‐a]azepine. The origin of the stereoselectivity is rationalized based on theoretical calculations. The concise synthesis of (−)‐(cis)‐3‐propylindolizidine and (−)‐(cis)‐3‐butyllehmizidine, two alkaloids found in the venom of workers of the ant Myrmicaria melanogaster, is reported., Enantiomerically enriched azabicyclic compounds found in several important families of alkaloids can be prepared by a remarkably stereospecific and stereoselective intramolecular Schmidt reaction. The initial asymmetric alcohol center controls the whole process, leading to the formation of one out of up to four possible diastereoisomers with inversion of the configuration at the original asymmetric center.

A very concise total synthesis of (+)-brefeldin C starting from 2-furanylcyclopentene is described. This approach is based on an unprecedented enantioselective radical hydroalkynylation process to introduce the two cyclopentane stereocenters in a single step. The use of a furan substituent allows a high trans diastereoselectivity to be achieved during the radical process and it contains the four carbon atoms C1-C4 of the natural product in an oxidation state closely related to the one of the target molecule. The eight-step synthesis requires six product purifications and it provides (+)-brefeldin C in 18 % overall yield.

A radiochemical procedure for the determination of plutonium (Pu) and uranium (U) radionuclides in ice samples by multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) is presented. Pu and U radionuclides are preconcentrated by coprecipitation and then separated by extraction chromatography. The purified Pu and U fractions are analyzed by MC-ICP-MS. Detection limits of 2 × 10 –3 and 3 × 10–6 mBq kg–1 were achieved for 239Pu and 236U, respectively. Surface ice samples collected from the Gauli glacier (Switzerland) were analyzed by this method. The surface of the Gauli Glacier retains historical records of 239Pu, 240Pu and 236U from the nuclear weapon testing (NWT) period. Pu and U radionuclides were found to be consistent in terms of pattern, showing two peaks possibly related to the two main periods of the NWTs (1954–1958 and 1961–1963). 3H measurements, also released by the NWT, further confirmed the Pu and U results. The 240Pu/239Pu ratio ranged from 0.14 to 0.25, and 236U/ 239Pu ranged from 0.14 to 0.81. The Pu atom ratios ranged within the limits of global fallout in the most intensive period of NWT (1952 to 1962).

The stereoselectivity and stereospecificity of the triflate mediated intramolecular Schmidt reaction of substituted 3-(1-azidocyclohexyl)propanol derivatives leading to octahydro-1H-pyrrolo[1,2-a]azepine, the structural skeleton of several important families of alkaloids such as the Stemona alkaloids, has been examined. The reaction involves an initial intramolecular SN2 reaction between the azide moiety and the triflate affording an intermediate spirocyclic aminodiazonoium salt that undergoes the expected 1,2-shift/N2-elimination followed by hydride mediated iminium salt reduction. Remarkably, chiral alcohols are converted to the azabicylic derivative with no or limited racemization. The initial asymmetric alcohol center controls the diastereoselectivity of the whole process leading to the formation of one out of the four possible diastereoisomers of disubstituted octahydro-1H-pyrrolo[1,2-a]azepine. The origin of the stereoselectivity is rationalized based on theoretical calculations. The concise synthesis of (–)-(cis)-3-propylindolizidine and (–)-(cis)-3-butyllehmizidine, two alkaloids found in the venom of workers of the ant Myrmicaria melanogaster, is reported.

The stereoselectivity of the triflate mediated intramolecular Schmidt reaction of substituted 3-(1-azidocyclohexyl)propanol derivatives leading to octahydro-1H-pyrrolo[1,2-a]azepine, the structural skeleton of several important families of alkaloids such as the Stemona alkaloids, has been examined. The reaction involves an initial intramolecular SN2 reaction between the azide moiety and the triflate affording an intermediate spirocyclic aminodiazonoium salt that undergoes the expected 1,2-shift/N2-elimination followed by hydride mediated iminium salt reduction. Remarkably, chiral alcohols are converted to the azabicylic derivative with no or limited racemization. The initial asymmetric alcohol center controls the diastereoselectivity of the whole process leading to the formation of one out of the four possible diastereoisomers of disubstituted octahydro-1H-pyrrolo[1,2-a]azepine. The origin of the stereoselectivity of is rationalized based on theoretical calculations.

A very concise total synthesis of (+)-brefeldin C starting from 2-furanylcyclopentene is described. This approach is based on an unprecedented enantioselective radical hydroalkynylation process to introduce the two cyclopentane stereocenters in a single step. The use of a furan substituent allows to achieve a high trans diastereoselectivity during the radical process and it contains the four carbon atoms C1–C4 of the natural product in an oxidation state closely related to the one of the target molecule. The eight-step synthesis require six product purifications and it provides (+)-brefeldin C in 18% overall yield.