Arthur Lütringhaus, Godfather of catenanes was born 120 years ago

Professor Arthur Lütringhaus is the pioneer of the chemistry of interlocked supramolecular systems, that he named catenates.

Arthur Lüttringhaus (1906-1992)

Lüttringhaus was a contemporary colleague of the great German cyclodextrin researcher team lead by Friedrich Cramer, at the University of Freiburg, between 1958–1988. This period is often called the „Einschlussverbindung”-(incusion complex formation) era.

The most seminal works of Lüttringhaus was to set up the principle of a novel chemical construction system, so-called catena compounds/catenanes (Latin catena = chain) also the synthesis and investigation of these unique interlocked supramolecular entities. Catenanes  consist of at least two rings, which behave like links in a chain relative to each other, without establishing any covalent bonds. So, catenanes are formed by the mechanical interlocking of two or more rings. The attempted synthesis of the first catenane was carried by Lüttringhaus and Cramer in 1958. During the synthesis they first isolated an inclusion complex between para-1,4-dithiol benzene and α-cyclodextrin. This complex was subsequently oxidized, forming a disulfide bound and thus closing the „guest ring”. (Figure 1) This very first synthesis, however, did not afford catenane. (1)

Figure 1 Attempted synthesis of a catenane in 1958 by Lüttringhaus and Cramer. (1)

Even if the first attempt to create catenanes, was a series of unsuccessful experiments, these pioneering works were recognized and acknowledged later by American researchers, by writing that “This experiment, despite its failure, has gone down in the history of catena chemistry as the very first attempt to synthesize such compounds”. (2)  The first really succesful isolation of a pure catenane was reported later, in 1964 by Gottfried Schill and Lüttringhaus (3).

Lütringhaus worked in Freiburg for many years, until 1988. On his 70th birthday, the university journal published a commemorative article, summarizing his outstanding achievements in organic supramolecular chemistry. However, it is interesting to mention that a complete list of Lütringhaus ‘s works does not exist. So far, 133 scientific publications and 13 patents have been documented. (5) The fundamentals that Lüttringhaus had laid in supramolecular chemistry led to the foundation of today’s chemical nanotechnology.

Today, seventy years after Schill and Lüttringhaus have accomplished the first synthesis of a catenane, a number of feasible synthetic strategies became known for the construction of different catena compounds, such as molecular „Hopf links”, (the simplest type of catenane) and higher order interlocked systems including „Solomon links,” „Borromean rings”, „Star of David” -type catenanes. (4) (See Figure 2)

Fig. 2 Historical development of different interlocked molecular entities, catenanes (4)

Interesting to note that catenanes occur in Nature, too. DNA catenanes are molecular structures composed of two interlocked circular DNA molecules, held together by a mechanical bond, a topological constraint arising from their mutual interlocking. DNA catenanes are transient intermediates in such processes as replication of circular DNA or transposon resolution. 6) By studying species of the formed catenanes, it is possible to get mechanistic insights into the termination process of DNA replication and into the mechanism of site-specific recombination. (6) Even the chemical synthesis of different catenated DNA nanostructures has been reported. See Fig.2. (7)

Figure 3 Illustration and AFM picture of DNA catenane nanostructures by Lohmann et al (7)

References

1. Lüttringhaus, A., Cramer, F. , Prinzbach, H., Henglein, F. M. (1958) Cyclisations of Long-Chain Dithiols. Experiments on the Formation of Encompassing Rings with the Aid of Inclusion Compounds. Justus Liebigs Ann. Chem. 613, 185–198.
2. Armspach, D., Ashton, P.R., Moore, C.P., Spencer, N., Stoddart, J.F., Wear, T.J. and Williams, D.J. (1993), The Self-Assembly of Catenated Cyclodextrins. Angew. Chem. Int. Ed. Engl., 32: 854-858.
   https://doi.org/10.1002/anie.199308541
3. Schill, G. and Lüttringhaus, A. (1964), The Preparation of Catena Compounds by Directed Synthesis. Angew. Chem. Int. Ed. Engl., 3: 546-547. https://doi.org/10.1002/anie.196405461
4. Gil-Ramírez, G., Leigh, D.A. and Stephens, A.J. (2015), Catenanes: Fifty Years of Molecular Links. Angew. Chem. Int. Ed., 54: 6110-6150. https://doi.org/10.1002/anie.201411619
5. Brückner, R. (2019), Pioneering Work on Catenanes, Rotaxanes, and a Knotane in the University of Freiburg 1958–1988. Eur. J. Org. Chem., 2019: 3289-3319. https://doi.org/10.1002/ejoc.201900268
6.  Sundin O, Varshavsky A. (1980) Terminal stages of SV40 DNA replication proceed via multiply intertwined catenated dimers. Cell. 21(1):103-14. https://doi.org/10.1016/0092-8674(80)90118-x. 
7. Lohman, F., Valero, J., Famulok,, M. (2014) A novel family of structurally stable double stranded DNA catenanes. Chem. Commun., 50: 6091-6093