A Formal Synthesis of (-)-Perhydrohistrionicotoxin Using a Cross Metathesis-Hydrogenation Approach.

The development of an efficient, high yielding six-step convergent synthesis of the semisynthetic alkaloid (-)-perhydrohistrionicotoxin is described. The key transformations include the cross metathesis of a Brønsted-acid masked primary homoallylic amine with a vinyl cyclohexenone and a regioselective palladium catalyzed hydrogenation. This sequence generated the advanced Winterfeldt spirocyclic precursor in 47% overall yield, with a longest linear sequence of five steps.

Tandem Ru-alkylidene-catalysed cross metathesis/hydrogenation: synthesis of lipophilic amino acids.

Highly efficient synthesis of lipidic amino acids can be achieved via Ru-alkylidene-catalysed cross metathesis of long chain alkenes with commercially available allylglycine. The resultant unsaturated analogues can be then optionally hydrogenated under mild reaction conditions by using the spent metathesis catalyst.

Lanthanoid-based ionic liquids incorporating the dicyanonitrosomethanide anion.

A series of low-melting-point salts with hexakisdicyanonitrosomethanidolanthanoidate anions has been synthesised and characterised: (C(2) mim)(3) [Ln(dcnm)(6)] (1 Ln; 1 Ln=1 La, 1 Ce, 1 Pr, 1 Nd), (C(2) C(1) mim)(3) [Pr(dcnm)(6)] (2 Pr), (C(4) C(1) pyr)(3) [Ce(dcnm)(6)] (3 Ce), (N(1114))(3) [Ln(dcnm)(6)] (4 Ln; 4 Ln=4 La, 4 Ce, 4 Pr, 4 Nd, 4 Sm, 4 Gd), and (N(1112OH) )(3) [Ce(dcnm)(6)] (5 Ce) (C(2) mim=1-ethyl-3-methylimidazolium, C(2) C(1) mim=1-ethyl-2,3-dimethylimidazolium, C(4) C(1) py=N-butyl-4-methylpyridinium, N(1114) =butyltrimethylammonium, N(1112OH) =2-(hydroxyethyl)trimethylammonium=choline). X-ray crystallography was used to determine the structures of complexes 1 La, 2 Pr, and 5 Ce, all of which contain [Ln(dcnm)(6)](3-) ions. Complexes 1 Ln and 2 Pr were all ionic liquids (ILs), with complex 3 Ce melting at 38.1 °C, the lowest melting point of any known complex containing the [Ln(dcnm)(6)](3-) trianion. The ammonium-based cations proved to be less suitable for forming ILs, with complexes 4 Sm and 4 Gd being the only salts with the N(1114) cation to have melting points below 100 °C. The choline-containing complex 5 Ce did not melt up to 160 °C, with the increase in melting point possibly being due to extensive hydrogen bonding, which could be inferred from the crystal structure of the complex.