Comparative structural analysis of sparteine derivatives and their protonated salts

Thioanalogs of Sparteine Lactams [6]. Part II. (+)-2-Thionosparteinium Perchlorate

“…Such an inver sion was found for example in sparteinium or multiflorinium perchlorates [2], The case of lupaninium salts is more sophisticated. On crystallization, they incorporate water molecules from the solution if crystallization does not proceed in strictly an hydrous environment.…”

“…Sparteine and its derivatives reveal some confor mational flexibility in the cis-C/D fragment which has been well recognized both in solution and in the solid state [1,2] (Scheme 1).…”

Enantioselective 1,3‐dipolar cycloaddition reactions using complexes of (−)‐sparteine

“…This alkaloid in a free form shows a transoid conformation with the C-ring in the boat form and trans C/D ring juncture [16,17]. On protonation or formation of metal complexes inversion of configuration on N-16 takes place resulting in adoption of cisoid conformation with cis C/D ring juncture [18,19] (Scheme 1), and a cavity between two nitrogen atoms allowing sparteine to function as a bidendate ligand.…”

17β-Isopropylsparteine and 17β-Isopropyllupanine Perchlorates

“…This semi-rigidity enables them to act as bidentate ligands, provided the N 16 atom can invert its configuration, converting ring C into a chair conformation in contrast to its boat form in the free base (see reaction scheme). In particular, the chelating properties of sparteine have been widely used in enantioselective organic syntheses (Borowiak & Wolska, 1996).…”