Núria Llor

Chiral precursors for the synthesis of enantiomerically pure piperidines. Total synthesis of (R)-(-)-coniine

Abstract The preparation of chiral cis - and trans -oxazolopiperidones 1 , 2 , and 3 by alternative procedures and an efficient synthesis of the piperidine alkaloid ( R )-(-)-coniine from trans - 1 is reported.

Preparation of enantiopure 6-(3-indolyl)-2-piperidones and conjugate additions to a 3,4-didehydro derivative

Amidoalkylation of chiral non-racemic lactams 1–3 with indole in the presence of TiCl4 provides enantiopure 6-(3-indolyl)-2-piperidones 4a,b–6a,b. The stereochemical course of the conjugate addition of a variety of functionalized carbon nucleophiles to 5,6-dihydro-2-pyridone 11, derived from 4a, is studied.

Synthesis of enantiopure piperidines. Total synthesis of (2R,6S)-2-methyl-6-propylpiperidine [(−)-dihydropinidine]

Abstract Enantiomerically pure 2-alkyl-, 3-alkyl-, 4-alkyl-, and cis -2,6-dialkylpiperidines are prepared from the chiral, non-racemic oxazolopiperidone 1 . An asymmetric synthesis of (2 R ,6 S )-(−)-dihydropinidine is reported.

A Synthetic Approach to Ervatamine-Silicine Alkaloids. Enantioselective Total Synthesis of (−)-16-Episilicine†

Starting from an appropriate unsaturated phenylglycinol-derived oxazolopiperidone lactam, the synthesis of (-)-16-episilicine is reported, the key steps being a stereoselective conjugate addition, a stereoselective alkylation, and a ring-closing metathesis reaction. This represents the first enantioselective total synthesis of an alkaloid of the silicine group.

Stereoselective α-amidoalkylation reactions of phenylglycinol-derived bicyclic lactams

The stereochemical outcome of α-amidoalkylation reactions from the chiral non-racemic bicyclic lactams trans-1 and cis-1 using indole, allyltrimethylsilane, higher order organocuprates, TMSCN, and Grignard reagents is discussed.

ENANTIOSELECTIVE SYNTHESIS OF THE TRANS-2,6-DIALKYLPIPERIDINE ALKALOIDS (2R, 6R)-LUPETIDINE AND (2R, 6R)-SOLENOPSIN A

Abstract The enantioselective synthesis of the trans -2,6-dialkylpiperidine alkaloids (2 R ,6 R )-lupetidine and (2 R ,6 R )-solenopsin A from 6-methyl-2-piperidone 1 is described. The key step of this synthesis consists of the addition of a dialkylcopper derivative to the thioimidate salt 3 followed by sodium borohydride reduction of the resulting iminium salt.

A concise procedure for the preparation of enantiopure 3-alkylpiperidines

Abstract Reaction of ( R )-phenylglycinol with racemic methyl 4-formylhexanoate takes place with a remarkable stereoselectivity to give two diastereomeric 6-ethyloxazolopiperidones (9:1 ratio) in 76% overall yield. After LiAlH 4 reduction and catalytic hydrogenation, the major isomer was converted to ( S )-3-ethylpiperidine.

A practical synthetic route to enantiopure 6-substituted cis-decahydroquinolines.

Starting from 4-substituted cyclohexanones, a practical synthetic route to enantiopure 6-substituted cis-decahydroquinolines has been developed, the key steps being a stereoselective cyclocondensation of an unsaturated δ-keto ester derivative with (R)-phenylglycinol and the stereoselective hydrogenation of the resulting tricyclic oxazoloquinolone lactams.

On the configuration of (3R, 8aS)-5-oxo-3-phenyl-2,3,6,7,8,8a-hexahydro-5H-oxazolo[3,2-a]pyridine

Abstract The configuration of (3R,8aS)-5-oxo-3-phenyl-2,3,6,7,8,8a-hexahydro-5H-oxazolo[3,2-a]pyridine 2 has been unambiguously confirmed by X-ray crystallographic analysis. A 1H NMR-based method for the stereochemical assignment of 3,8a-cis and trans phenylglycinol-derived bicyclic lactams is also proposed.

Enantio‐ and Diastereoconvergent Cyclocondensation Reactions: Synthesis of Enantiopure cis‐Decahydroquinolines

Up to four stereocenters with a well-defined configuration are generated in a single synthetic step by the cyclocondensation of (R)-phenylglycinol or (1S,2R)-1-amino-2-indanol with stereoisomeric mixtures (racemates, meso forms, diastereoisomers) of cyclohexanone-based δ-keto-acid and δ-keto-diacid derivatives in enantio- and diastereoconvergent processes that involve dynamic kinetic resolution and/or desymmetrization of enantiotopic groups. A detailed analysis of the stereochemical outcome of this process is presented. This method provides easy access to enantiopure 8- and 6,8-substituted cis-decahydroquinolines, including alkaloids of the myrioxazine family.