Strigolactones (SLs) are a new class of plant hormones whose role has been recently defined in shoot branching, root development and architecture, and nodulation. They are also active in the rhizosphere as signalling molecules in the communication between plants, AMF (arbuscular mycorrhizal fungi) and parasitic weeds. In spite of the crucial and multifaceted biological role of SLs, the current knowledge on the SL biosynthetic pathway and the perception/transduction mechanism is still incomplete. Both genetic and molecular approaches are required to understand the molecular mechanism by which SLs regulate plant development. Our contribution to this topic is the design and synthesis of fluorescent labelled SL analogues to be used as probes for the detection in vivo of the receptor(s). Knowledge of the putative receptor structure will boost the research on analogues of the natural substrates as required for agricultural applications.

The gold(I)‐catalysed reaction of N‐Boc‐protected 6‐alkynyl‐3,4‐dihydro‐2H‐pyridines, which gives synthetically useful vinylogous amides (β‐enaminones), has been studied in detail, in order to optimize the reaction conditions, enlarge the scope and gain insight into the mechanism and the structural features that selectively favour the 6‐endo‐dig oxyauration of the triple bond. Experimental studies and DFT calculations demonstrate that the 6‐endo‐dig approach is exclusive with substituted alkynes, whereas with terminal alkynes the 5‐exo‐dig cyclization prevails, despite the large angle (120°) at C‐6. The same selectivity was observed with N‐Cbz‐protected 2‐alkynylpiperidines. With these compounds, β‐amino ketones are obtained as a consequence of the 6‐endo‐dig attack onto a substituted triple bond. Sedamine alkaloids are easily obtained by this approach.

A short synthesis of both enantiomers of trans‐3‐hydroxypipecolic acid was based on the Suzuki–Miyaura reaction of a lactam‐derived enol phosphate and the lipase‐catalyzed kinetic resolution of the alcohol obtained by hydroboration/oxidation of the coupling product. The RuCl3‐catalyzed oxidation of the heteroaryl group introduced by the Suzuki–Miyaura coupling eventually afforded, in six or seven steps, the target compounds in 15–17 % overall yield.

Gold-Catalyzed Synthesis of Exocyclic Vinylogous Amides and -Amino Ketones:A Detailed Study on the 5-exo/6-endo-dig Selectivity, Methodology and Scope. -The Au(I)-catalyzed reaction of N-Boc-protected 6-alkynyl-3,4-dihydro-2H-pyridines, giving vinylogous amides (-enaminones), is studied in detail. Experimental studies and DFT calculations demonstrate that the 6-endo-dig approach is exclusive with substituted alkynes, whereas with terminal alkynes 5-exo-dig cyclization prevails. The same selectivity was observed with N-Cbz-protected 2-alkynylpiperidines to afford -amino ketones due to a 6-endo-dig attack onto a substituted triple bond. Sedamine alkaloids become easily accessible based on this method. -(SCARPI*, D.; BEGLIOMINI, S.; PRANDI, C.; OPPEDISANO, A.; DEAGOSTINO, A.; GOMEZ-BENGOA, E.; FISER, B.; OCCHIATO, E. G.; Eur. J. Org. Chem. 2015, 15, 3251-3265, http://dx.doi.org/10.1002/ejoc.201500205 ; Dip. Chim., Univ. Stud. Firenze, I-50019 Sesto Fiorentino, Italy; Eng.) -T. Stabingis 37-172Cl -