Helena Almer

Intramolecular transesterification in thiophosphate-analogues of an RNA-dimer.

Abstract The differences in rates for cleavage of uridylyl(3′-5′) uridine and the uridin-3′-yl uridin-5′-yl thiophosphates (Rp and Sp-diastereomers) have been measured. The ratios of rates are: k(phosphate)/ k(Rp-thiophosphate)= 1.3; k(phosphate)/k(Sp-thiophosphate)= 0.78; k(Sp-thiophosphate)/k(Rp-thio-phosphate)= 1.7 and they were found to be independent of pH in the pH-range 9–12. The results are also dicussed in the context of using thiophosphates in kinetic studies of enzymatic systems involving transesterification of phosphodiesters.

2-CYANOETHYL H-PHOSPHONATE. A REAGENT FOR THE MILD PREPARATION OF NUCLEOSIDE H-PHOSPHONATE MONOESTERS

Abstract 2-Cyanoethyl H-phosphonate was condensed with protected nucleoside derivatives and the cyanoethyl group subsequently removed by anhydrous base to give the corresponding nucleoside H-phosphonate in good yield.

A new approach to stereospecific synthesis of P-chiral phosphorothioates. Preparation of diastereomeric dithymidyl-(3?-5?) phosphorothioatesElectronic supplementary information (ESI) available: synthesis and characterization of compounds 2 through 6. See http://www.rsc.org/suppdata/cc/b3/b311912b/

A new method for stereospecific synthesis of P-chiral phosphorothioates based on intramolecular nucleophile catalysis was developed.

Chemical Synthesis of RNA-Fragment Analogues That Have Phosphorothioate Linkages of Identical Configuration

Abstract Oligouridine all-Rp-phosphorothioates were synthesized using the H-phosphonate approach followed by sulfurisation with S8 and treatment with nuclease P1. The degree of stereoselection in the couplings is reported for different 2′-O-silyl protecting groups. The influence of the heterocyclic base was also investigated.

RNA-Synthesis Using the H-Phosphonate Approach and an Improved Protecting Group Strategy

Abstract An improved version of the H-phosphonate approach to RNA-synthesis is presented and the studies that led to alterations in the protecting group strategy are discussed.

Nonenzymatic Hydrolysis of an RNA-DIMER Containing a Thiophosphate Linkage

Abstract A Diuridine (3′-5′)-thiophosphate (1b) was hydrolyzed under basic conditions. The rate of hydrolysis of the uridylyl (3′-5′)- uridine (1a) was three times higher compared to that of 1b.