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The (+)- as well as the (−)-enantiomer of the pyrrolizidine alkaloid xenovenine were prepared within five steps with 17 and 30% overall yields, respectively, in optically pure form, >99% ee as well as >99% de. In the asymmetric key step a transaminase performed a regio- and stereoselective monoamination of a triketone. By employing two enantiocomplementary transaminases from Arthrobacter sp. both enantiomers were accessible. The triketone was readily prepared via two steps starting from commercially available, achiral 2-( n-heptyl)furan. In the final catalytic hydrogenation step, the newly introduced chiral centre directed hydrogen addition to form preferentially the desired (5 Z,8 E)-diastereomer. The regio- and stereoselective amination of a single ketone moiety out of three allowed the performance of the shortest and highest yielding total synthesis of the bicyclic showcase pyrrolizidine alkaloid without the need for protecting strategies. [ABSTRACT FROM AUTHOR]

For example, the (-)-enantiomer of xenovenine (IV) is prepared starting from triketone (I) through a short and high-yielding total synthesis without the need for protecting strategies. [ABSTRACT FROM AUTHOR]

The front cover picture, designed by Verena A. Resch and Stefan Payer, illustrates creating three stereocenters in two steps: the regio ‐ and stereoselective mono ‐ amination of a prochiral triketone followed by chemical reduction gave access to xenovenine, the venom of the ant species Solenopsis tennesseensis. Each enantiomer can be accessed by switching from an (S) ‐ to an (R) ‐ selective biocatalyst in the asymmetric key step of the sequence. Details can be found in the Full Paper on pages 444 – 451 (S. E. Payer, J. H. Schrittwieser, B. Grischek, R. C. Simon, W. Kroutil, Adv. Synth. Catal.­ 2016, 358, 444 – 451; DOI: 10.1002/adsc.201500781). The authors acknowledge supported by the University of Graz for the printing of the cover picture. [ABSTRACT FROM AUTHOR]