I. Tömösközi

Stereospecific conversion of H-phosphonates into phosphoramidates. The use of vicinal carbon-phosphorus couplings for configurational determination of phosphorus

Abstract Separated P-diastereomers of H-phosphonate diesters gave exclusively one isomer of amidates on treatment with CCl 4 + butylamine with inversion of configuration. NOE experiments and the trend observed in 3 J(C2-P) and 3 J(C4-P) couplings were applied for stereochemical assignment. Separated P-diastereomers of H-phosphonate diesters gave exclusively one isomer of amidates on treatment with CCl 4 + butylamine with inversion of configuration. NOE experiment and the trend observed in 3 J(C2-P) and 3 J(C4-P) couplings were applied for stereochemical assignment

Regiospecific prins reaction, a new way to prostanoids

Aus dem bicyclischen Lacton (I) erhalt man bei der Prins-Reaktion mit Formaldehyd und Saure uber die Zwischenstufe (II) stereospezifisch die Addukte (IIIa) im Gemisch mit den Monoacetaten (IIIb) und (IIIc).

Synthetic studies towards (−)-carba-3′-deoxy-3′-fluorothymidine.

Abstract Stereospecific synthesis of (−)-carba-3′-deoxy-3′-fluorothymidine (−)- 11 is reported from the protected (−)-carbocyclic 3′-epi-thymidine (−)- 7 using diethylaminosulfur trifluoride. Under the conditions used, extensive dehydration of the blocked precursor into 10 and formation of the 4′-fluoro analogue ( 9 ) were also observed. An attempted simplification of our methodology based on (+)-(1R, 5S)-2-oxabicyclo[3.3.0]oct-6-en-3-one failed, but a novel cyclopentane ( 2 ) ring expansion to tetrahydropyran ( 18 ) was discovered.

Configurational determination and conformational properties of diastereomeric nucleoside-phosphorothioates

Abstract The determination of configuration at phosphorous in enantiomerically pure nucleoside-phosphorothioates is reported. T-ROESY experiments and the trend observed in vicinal carbon-phosphorus couplings were used for stereochemical assignment.

Asymmetric synthesis—IV : Quantitative interpretation of stereoselectivity in the reaction of hydratropic anhydride with optically active amines

Abstract The extent of kinetic resolution in the reaction of hydratropic anhydride with seven optically active amines was determined. Experimental results are in good agreement with values calculated from the Ugi equation. Modification of the definition of “positive” and “negative” diastereomers is suggested.

Synthesis and stereochemical characterization of diastereomeric nucleoside-phosphorothioselenoates by NMR methods

Synthesis and stereochemical characterization of enantiomerically pure nucleoside-phosphorothioselenoates are reported. The effects of solvent and temperature on the vicinal carbon-phosphorus couplings are described and the results are interpreted in terms of conformational changes influenced by stacking interactions between the bases and the phenyl rings.

A convenient short synthesis of 7-oxo-PGI2

Abstract A 5-step synthesis of the title compound via selective hydroxylation of Δ 6 -PGI 1 derivative is presented including stereochemistry and conformational analysis of intermediates.

Prins reaction of 2-oxabicyclo[3.3.0]oct-6-en-3-one and related derivatives

Abstract Reaction of formaldehyde with the title olefinic lactone in acetic acid affords diacetate of 1,3-diol ( 2a ) as the main product in 50 – 60% yield via regioselective trans-addition. Less favourable results were obtained with related bicyclic derivatives.

Spontaneous dihydroxylation of α-oxo enol ethers by air

Abstract Unexpected dihydroxylation of 7-oxo-prostacyclin and a related α-oxo enol ether by air is reported.

Remote OH-group directing effect in the stereochemistry of intramolecular alkoxide addition to conjugated double bond

Abstract Preferential formation of less stable (endo) product in intramolecular Michael reaction is explained by the participation of structurally remote OH group in the transition state.