Asymmetric synthesis of (−)-(S,S)-homaline

One-Step Diastereoselective Pyrrolidine Synthesis Using a Sulfinamide Annulating Reagent

This communication highlights the use of chiral sulfinamides as nitrogen nucleophiles in intermolecular aza-Michael reactions. When chiral sulfinamides are coupled to a chloroethyl group, the corresponding novel annulating reagents can be used to streamline the stereoselective synthesis of complex pyrrolidine-containing molecules. As a result, it has enabled a medicinal chemistry campaign for the synthesis of biologically active RORγt inverse agonists.

Diastereoselective auxiliary- and catalyst-controlled intramolecular aza-Michael reaction for the elaboration of enantioenriched 3-substituted isoindolinones. Application to the synthesis of a new pazinaclone analogue

A new asymmetric organocatalyzed intramolecular aza-Michael reaction by means of both a chiral auxiliary and a catalyst for stereocontrol is reported for the synthesis of optically active isoindolinones. A selected cinchoninium salt was used as phase-transfer catalyst in combination with a chiral nucleophile, a Michael acceptor and a base to provide 3-substituted isoindolinones in good yields and diastereomeric excesses. This methodology was applied to the asymmetric synthesis of a new pazinaclone analogue which is of interest in the field of benzodiazepine-receptor agonists.

The homalium alkaloids: isolation, synthesis, and absolute configuration assignment

The structurally related natural products (-)-homaline, (-)-hopromine, (-)-hoprominol, and (-)-hopromalinol have been collectively termed the homalium alkaloids. All four alkaloids possess bis-ζ-azalactam structures, but differ only by the identities of the side chain on each lactam ring. Since their isolation (from the leaves of Homalium pronyense Guillaum found in the forests of New Caledonia), there have been several syntheses of homaline, hopromine, hoprominol, and hopromalinol in both racemic and enantiopure forms. The most highly yielding and versatile strategy for their synthesis employs the conjugate addition of an enantiopure lithium amide reagent to an α,β-unsaturated ester as the key stereodefining step. This methodology has been used in the syntheses of all four members of the homalium alkaloid family and their stereoisomers.

To be or not to be butterfly: New mechanistic insights in the Aza-Michael asymmetric addition of lithium (R)-N-benzyl-N-(α-methylbenzyl)amide

The asymmetric Aza-Michael addition of homochiral lithium benzylamides to α,β-unsaturated esters represents an extended protocol to obtain enantioenriched β-amino esters. An exhaustive mechanistic revision of the originally proposed mechanism is reported, developing a quantum mechanics/molecular mechanics protocol for the asymmetric Aza-Michael reaction of homochiral lithium benzylamides. Explicit and implicit solvent schemes were considered, together with a proper account of long-range dispersion forces, evaluated through a density functional theory benchmark of different functionals. Theoretical results showed that the diastereoselectivity is mainly controlled by the N-α-methylbenzyl moiety placing, deriving a Si/Re 99:1 diastereoselective ratio, in good agreement with reported experimental results. The main transition state geometries are two transition state conformers in a "V-stacked" orientation of the amide's phenyl rings, differing in the tetrahydrofuran molecule arrangement coordinated to the metal center. Extensive conformational sampling and quantum-level refinement give reasonable good speed/accuracy results, allowing this protocol to be extended to other similar Aza-Michael reaction systems.

Asymmetric synthesis of (-)-martinellic acid

A high-yielding total asymmetric synthesis of (-)-martinellic acid is reported. The conjugate addition of lithium (R)-N-allyl-N-(α-methyl-4-methoxybenzyl)amide to tert-butyl (E)-3-[2'-(N,N-diallylamino)-5'-bromophenyl]propenoate and alkylation of the resultant β-amino ester have been used as the key steps to install the C(9b) and C(3a) stereogenic centers, respectively, and a highly diastereoselective Wittig reaction/intramolecular Michael addition was then used to create the C(4) stereogenic center within this tricyclic molecular architecture.