Anne Paju

Asymmetric Baeyer-Villiger oxidation of cyclobutanones

Abstract The asymmetric Baeyer-Villiger oxidation of racemic cyclobutanones 1, 2, and 3 and a prochiral cyclobutanone 4 under Sharpless oxidation conditions resulted in the enantiomeric lactones 5 ee 34%, 6 ee 53%, 7 ee 75% and 8 40% ee respectively.

Asymmetric oxidation of cyclobutanones: modification of the Sharpless catalyst

Abstract Oxidation of prochiral and racemic cyclobutanones with t-BuOOH and Ti–TADDOL-based complexes afforded lactones in up to 44% ee. The enantioselectivity of the reaction clearly depends on the amount of the reagent and the highest enantioselectivities were obtained with stoichiometric amounts of the complex. Modification of the TADDOL structure and use of the mixed complex derived from TADDOL and a tartaric ester led to more reactive but less selective oxidation systems.

Asymmetric oxidation of 3-alkyl-1,2-cyclopentanediones. Part 2: Oxidative ring cleavage of 3-alkyl-1,2-cyclopentanediones: synthesis of 2-alkyl-γ-lactone acids

Abstract Ti(O i Pr) 4 /diethyl tartrate/ t BuOOH system oxidizes 3-alkyl-1,2-cyclopentanediones resulting in hydroxylated ring cleavage products 2-alkyl-γ-lactone acids, in high enantioselectivity (∼95% ee) and satisfactory isolated yields (up to 55%).

Asymmetric oxidation of 1,2-cyclopentanediones

Abstract Cyclic 3-alkyl-1,2-cyclopentanediones undergo a direct asymmetric oxidation with the DET/Ti(OiPr)4/tBuOOH oxidative system, resulting in enantiomeric α-hydroxy compounds and ring-cleaved hydroxylated acids (lactones) up to 95% ee.

Direct asymmetric α-hydroxylation of β-hydroxyketones

Abstract Direct oxidation of racemic β-hydroxyketones 1a-c under Sharpless oxidation conditions resulted in the enantiomeric α,β-dihydroxyketones 2a in 97% ee, 2b in 86% ee and 2c in 95% ee respectively, in 37–58% of isolated yield. The oxidation is assumed to proceed via an allylic enolate intermediate.

Asymmetric oxidation of 3-alkyl-1,2-cyclopentanediones. Part 1: 3-Hydroxylation of 3-alkyl-1,2-cyclopentanediones

Abstract 3-Alkyl-1,2-cyclopentanediones undergo asymmetric 3-hydroxylation with the Sharpless Ti-complex resulting in enantiomeric 3-hydroxy carbonyl compounds with ee up to 95% in yields of 22–40%.

Synthesis of Novel Acyclic Nucleoside Analogues with Anti-Retroviral Activity

A series of novel acyclic thymine nucleoside analogues were prepared by the Mitsunobu reaction from appropriately protected chiral triols. The enantiomeric triols were obtained from substituted γ-lactone acids, prepared by asymmetric oxidation of 3-substituted-1,2-cyclopentanediones. The cytotoxic activity of new analogues was evaluated on MCF-7 human breast cancer and HeLa cells, and antiviral activities on human immunodeficiency virus type 1 and hepatitis C virus models. The synthesized compounds revealed specific anti-retroviral activity and no cytotoxic side effects.

Direct asymmetric α-hydroxylation of 2-hydroxymethyl ketones

A direct α-hydroxylation of racemic 2-hydroxymethyl ketones with the Sharpless epoxidation catalyst resulted in α,β-dihydroxy ketones in high ee (up to 97%) and in moderate to good isolated yield (up to 58%).

Asymmetric oxidation of 3-alkyl-1,2-cyclopentanediones. Part 3: Oxidative ring cleavage of 3-hydroxyethyl-1,2-cyclopentanediones: synthesis of α-hydroxy-γ-lactone acids and spiro-γ-dilactones

Abstract A Ti(O i Pr) 4 /diethyl tartrate/ t BuOOH complex oxidizes 3-hydroxyethyl-1,2-cyclopentanediones, resulting in hydroxylated/ring cleavage products—lactone acids of high enantioselectivity (up to 95% ee) with good yields (up to 75%). These compounds are converted into chiral spiro-γ-dilactones in good yield.

Analogues of thromboxane A2

Abstract A synthesis of 7[3(3R-hydroxy-3-cyclohexyl-l-propyl)-7-oxa-lS,2S,3S,4-R-bicyclo[2.2.1]-heptan-2-yl-5Z-heptenoic acid 1, an ω-chain saturated analogue of Thromboxane A2 is described. The relative and the absolute configurations of the intermediates and the target compound were determined by 2D FT NMR methods.