Electrospray deposition in vacuum

We have used the established technique of electrospray in developing a portable vacuum electrospray system which can deposit, in vacuo, dissolved molecules onto a sample which may then be analysed by UHV techniques. As an initial test of the system we have analysed silicon samples with an electrosprayed layer of poly(ethylene) oxide (PEO) using atomic force microscopy (AFM). The polymer forms different structures depending on the voltage applied to the emitter, and solution composition. The system is part of our ongoing effort to deposit other materials such as nanoparticles, and large dye molecules for developing molecular dye sensitised solar cells.     

Selective methodologies for the synthesis of biologically active piperidinic compounds

The synthesis of optically active substituted piperidines has been achieved by using four different methodologies. The first one is an intramolecular nucleophilic displacement of activated alcohol moieties that was used to build up the piperidine ring of (-)-prosophylline and (-)-slaframine, and the second one is a ring-closing metathesis of unsaturated amines which was employed in the synthesis of (+)-sedamine and 4a,5-dihydrostreptazoline. The third methodology is the alpha-functionalization of N-Boc piperidines which was particularly useful in the synthesis of argatroban, and the fourth one is a ring expansion of prolinols to 3-chloropiperidines or 3-hydroxypiperidines which was utilized to synthesize (-)-paroxetine, (-)-pseudoconhydrine, the piperidine ring of (-)-velbanamine and (+)-zamifenacin.     

Two approaches for efficient synthesis of (−)-colletol

The synthesis of (−)-colletol was achieved from (R)-pent-4-en-2-ol by using enantioselective allyltitanations to control the stereogenic centers at C5 and cross-metathesis, ring-closing metathesis reactions to control the configuration of the double bonds.     

Enantioselective monoreduction of 2-alkyl 1,3-diketones using chiral ruthenium catalysts. Synthesis of the C14C25 fragment of bafilomycin A1

The enantioselective monoreduction of 2-alkyl 1,3-diketones by dynamic kinetic resolution using optically active ruthenium catalysts allowed the preparation of the C14-C25 fragment of bafilomycin A₁.     

Generation of ketyl radical anions by photoinduced electron transfer (PET) between ketones and amines. Synthetic applications

Photoreduction of ketones in the presence of amines led to ketyl radicals through photoinduced electron transfer (PET). Tertiary amines, such as triethylamine (Et₃N) have frequently been used in these reactions. Different reactions can occur from ketyl radicals such as photoreduction, coupling reactions, additions on activated double bonds, cyclizations, bond cleavage of strained rings, tandem reactions such as cyclization-ring opening or ring opening-cyclization.     

Total synthesis of zincophorin methyl ester

[reaction: see text]. A convergent total synthesis of the methyl ester of zincophorin, an ionophore antibiotic, has been realized relying on a diastereoselective titanium-mediated aldol coupling between the C1-C12 and C13-C25 subunits. The latter fragment was prepared by using a Carroll-Claisen rearrangement.