Aleksander-Mati Müürisepp

New cytotoxic sterols from the soft coral Gersemia fruticosa

Abstract Six new polyoxygenated sterols 1–6 were isolated from the soft coral Gersemia fruticosa. The structures of these compounds were determined by MS. 1H- and 13C- 1D and 2D FT NMR spectroscopy. Compounds 1–6 showed a moderate cytotoxic activity against human erythroleukemia K-562 cells and other leukemia cell lines.

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 synthesis of novel C2-symmetric bimorpholines

Abstract Novel heterocycles—(2S,2′S)-bimorpholine 1 and (3S,3′S)-bimorpholine 2—were synthesised in >98% e.e. starting from tartaric acid ester.

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%.

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.

C2-Symmetric bimorpholines as chiral ligands in the asymmetric hydrogenation of ketones

Abstract 2,2′-Bimorpholine and 3,3′-bimorpholine were used as chiral ligands in Rh-mediated asymmetric hydride transfer reduction of prochiral aromatic ketones affording corresponding alcohols with good ee (up to 75%).

Synthesis of chiral epoxyalkynes

Abstract The synthesis of novel chiral propargylic epoxides (( R )-1- t -butyldimethylsilyl-3,4-epoxy-1-butyne, (3 S ,4 S )-3,4-epoxy-1-octyne, (3 R ,4 S )-1- t -butyldimethylsilyl-3,4-epoxy-1-pentyne) has been developed starting from the readily available tartaric acid derivative, ( S,S )-(+)-2,3-O-isopropylidene-L-threitol.

Synthesis and Quantitative Analysis of Diastereomeric Linked Ester Conjugates With Remote Stereocenters Using High-Field NMR and Chiral HPLC

A stereochemically safe high-yielding procedure for linking unprotected as well as protected hydroxycarboxylic acids to chiral secondary alcohols via glycolic acid linker is proposed. L-menthol has been linked with both enantiomers of mandelic, malic, and methoxyphenylacetic acid using bromo- or iodoacetyl group as a precursor of the glycolic acid linker. High-field nuclear magnetic resonance (NMR) and chiral high-performance liquid chromatography (HPLC) determination of high diastereomeric ratio (dr) (>99%) of the products bearing remote stereocenters was explored. Chiral HPLC allowed quantitation of the diastereomers up to dr 99.9/0.1. High-field NMR quantitation of the diastereomeric and parent alcoholic impurities in esters was demonstrated at the molar 0.3% and 0.03% levels, respectively. These analyses were done via comparison of integral intensities from major component (13)C satellites in (1)H or even in (13)C spectra to the (1)H or (13C signals of impurities. Despite lower sensitivity, the last option generally has much better selectivity. In this way the dynamic resolution is brought down by two orders.

SYNTHESIS OF 5,5'-DISUBSTITUTED BIMORPHOLINES

A general method for the synthesis of 5,5′-disubstituted bimorpholines is proposed. According to the method, methyl-substituted and benzyl-substituted compounds were synthesized, starting from tartaric ester acetal. Target compounds were obtained in good yield and high enantiomeric purity.

Stereoselective synthesis of 1-methyl-1,2-and 1,3-cyclopentanediols via γ-lactones

A method for the synthesis of 1-methylcarbapentofuranose derivatives was developed, where 1,2-cis- and 1,2-trans-4-hydroxymethyl-1-methylcyclopentanediols were obtained from intramolecular opening of a 4-epoxy-4-methyl-γ-lactone. An intramolecular aldol reaction of 4-methyl-4-(2-oxoethyl)-γ-lactone derivatives yielded 1,3-cis- and 1,3-trans-4-hydroxymethyl-1-methylcyclopentanediols.