Regio- and Stereoselective Aminopentadienylation of Carbonyl Compounds

Efforts toward the Total Synthesis of Elisabethin A

We describe our efforts toward the total synthesis of the natural product elisabethin A. The first route was guided by the proposed biosynthesis, assembling the 6,6-ring system before forming the five-membered ring including the quaternary carbon. The second approach includes a high yielding cyclization under Mitsunobu conditions as a key step. It allowed the preparation of an unusual and highly functionalized bicyclic 6,5-spiro compound. Both routes share a common advanced precursor obtained from an "underdeveloped" Claisen rearrangement of an aryl dienyl ether.

Chiral N-tert-Butylsulfinyl Imines: New Discoveries

In this account the reactions of chiral N-tert-butylsulfinyl imines with organometallic reagents such as organoalkaline (lithium, sodium, potassium and cesium derivatives), organomagnesium, organozinc, organoboron, organoaluminium, organoindium and organosilicon compounds is comprehensively described. The reactivity in all cases is derived to synthetic applications in order to prepare interesting organic nitrogenated molecules, especially in the field of alkaloid compounds.

Single or Synergistic Kinetic Resolutions of Chiral Allylalanes: Two Complementary Routes for the Asymmetric Synthesis of Syn Homoallylamines

Two strategies based on kinetic resolution(s) of chiral alanes and providing enantioenriched syn homoallylamines are reported. The first implies a single kinetic resolution of the alane using camphor; the second requires two sequential kinetic resolutions using the synergistic combination of (-)-camphor/(R)-tert-butylsulfinamide-derived imines. This syn selectivity, specific to the use of allyaluminum, opens the way to the preparation of valuable building blocks as illustrated by the synthesis of (+)-epilupinamine.

α-Trifluoromethylated tertiary homoallylic amines: diastereoselective synthesis and conversion into β-aminoesters, γ- and δ-aminoalcohols, azetidines and pyrrolidines

The diastereoselective addition of allyl zinc and allylindium derivatives to α-trifluoromethyl N-tert-butanesulfinyl hemiaminals, bench stable precursors of aryl and alkyl trifluoromethyl ketimines, allows the synthesis of homoallylic amines containing a tetrasubstituted carbon stereocentre bearing a trifluoromethyl group with good diastereoselectivities (up to dr > 99 : 1). This approach was also suitable for accessing chiral homoallylic amines bearing two contiguous stereocenters. The synthetic usefulness of N-tert-butanesulfinyl homoallylamines was illustrated by preparing various trifluoromethylated nitrogen containing bifunctional synthons (aminoesters, aminoalcohols) and small azaheterocycles (azetidines, pyrrolidines).

Concise asymmetric syntheses of novel phenanthroquinolizidines

The first preparation of enantioenriched phenanthroquinolizidines with a quaternary center at C14a was accomplished in seven steps from readily available starting materials. Key steps were an efficient dynamic kinetic allylation of a diastereomeric mixture of chiral tert-butylsulfinyl ketimines and the construction of a piperidine E ring by rhodium catalyzed hydroformylation. The Stevens rearrangement of the corresponding N-benzyl derivatives took place smoothly, allowing the installation of a benzyl moiety at C9 in a trans relationship with the methyl group. The cytoxicity of the prepared phenanthroquinolizidines was evaluated against different human cancer cell lines.

Short asymmetric synthesis of phenanthroindolizidines through chiral homoallylic sulfinamines

An efficient stereocontrolled preparation of chiral phenanthroindolizidines is detailed. The synthesis relies on the stereoselective indium-mediated allylation of 2-(phenanthren-9-yl)acetaldehyde derivatives with chiral tert-butylsulfinamide. Chemoselective transformations from the corresponding homoallylic sulfinamine allow the synthesis of the phenanthroindolizidines in only three synthetic operations, without any detectable racemization. Following this procedure, the synthesis of natural (-)-tylophorine was successfully accomplished.

Asymmetric intramolecular aza-Michael reaction in desymmetrization processes. Total synthesis of hippodamine and epi-hippodamine

The use of chiral sulfinyl amines both as nucleophilic nitrogen sources and chiral inducers has been described for the first time in a desymmetrization-type process involving an intramolecular aza-Michael reaction. The resulting product was employed as an advanced intermediate in the total synthesis of the natural product hippodamine and epi-hippodamine, taking advantage of the special symmetry of these molecules. In addition, this is the first asymmetric total synthesis of epi-hippodamine.

Scalable asymmetric synthesis of a key fragment of Bcl-2/Bcl-xL inhibitors

We describe a novel asymmetric synthesis, which is applicable on a large-scale, of a chiral diamine useful as a common fragment of numerous Bcl-2 and Bcl-_xL inhibitors.