Stereocontrolled Synthesis of Enantiopure Substituted 4-Aminopyrrolidin-2-ones

Investigation into Direct use of Protected 3,4-Dehydropyroglutamates in Synthesis

Synthesis of the 3,4-dehydropyroglutamate 5 has shown it to be unstable, forming the dimer 9 on chromatography and being too readily racemised to be considered as a useful chiral synthon.

2-Pyrrolidinones and 3-Pyrrolin-2-ones: A Study on the Chemical Reactivity of These Structural Moieties

The chemical reactivity of 2-pyrrolidinones and 3-pyrrolin-2-ones was evaluated in reactions of addition, nucleophilic substitution, elimination, and reduction as well as the protection of the lactamic nitrogen.

Synthesis of Functionalized Pyrrolidin-2-ones and (S)-Vigabatrin from Pyrrole

Starting from pyrrole, the novel 3,4-didehydropyrohomoglutamate 8 or (ent)-8 can be efficiently synthesized in up to 91% ee, which can be utilized as a versatile building block toward functionalized pyrrolidin-2-ones. Moreover, (ent)-8 can be readily converted to (S)-Vigabatrin, being an irreversible inhibitor for GABA-T, which is used as adjunctive therapy in patients that suffer from epilepsy.

Diastereoselective syntheses of deoxydysibetaine, dysibetaine, and its 4-epimer

(+/-)-Deoxydysibetaine 2 and 4-epi-dysibetaine 3 were prepared in a few steps from methyl pyroglutamate through a regioselective Mannich reaction at C-2. Natural (2S,4S)-dysibetaine 1, a sponge metabolite isolated from Dysidea herbacea, and (2S)-2 were synthesized from enantiopure (S)-pyroglutaminol with very high stereoselectivity. The key steps were an original formation of stereogenic quaternary center C-2 and the diastereoselective hydroxylation at C-4.

Pyrrolidinones derived from (S)-pyroglutamic acid: penmacric acid and analogues

Alkylation reactions using alpha-halolactams or lactam enolates derived from bicyclic lactam templates can proceed with high endo- or exo- diastereoselectivity respectively. In the latter case, stereochemical correction by means of enolate generation and hindered phenol quench is possible with moderate efficiency. This protocol has been applied to the synthesis of protected penmacric acid and its analogues.

Reaction between N-alkylhydroxylamines and chiral enoate esters: more experimental evidence for a cycloaddition-like process, a rationale based on DFT theoretical calculations, and stereoselective synthesis of new enantiopure beta-amino acids

The reactions between N-benzyl- and N-methylhydroxylamine and chiral enoate esters, derived from D-glyceraldehyde and (-)-verbenone, respectively, have been investigated. Theoretical calculations show that the most favorable mechanism involves the concerted cycloaddition of the hydroxylamine to the substrate. This result is in good agreement with the stereospecificity observed when the trisubstituted olefins are used. The open-chain adducts have been isolated when the processes are carried out at low temperatures and for short reaction times. These compounds evolve to the corresponding isoxazolidinones on standing at room temperature or under acid catalysis. The high pi-facial diastereoselection has been rationalized on the basis of steric effects induced by the dioxolane ring for D-glyceraldehyde derivatives or by the cyclobutane gem-dimethyl substitution for esters prepared from (-)-verbenone. As an application of these reactions, new beta-amino acids have been synthesized in a highly efficient and stereocontrolled manner.