Abstract: A process for the synthesis of a phosphorothioate triester is provided. The process comprises the coupling of an H-phosphonate with an alcohol in the presence of a solution comprising both a coupling agent and a sulfur transfer agent. Preferably, the H-phosphonate and alcohol are protected nucleosides or oligonucleotides.

Abstract: A process for the synthesis in solution phase of a phosphorothioate triester is provided. The process comprises the solution phase coupling of an H-phosphonate with an alcohol in the presence of a coupling agent to form an H-phosphonate diester. The H-phosphonate diester is oxidised in situ with a sulfur transfer agent to produce the phosphorothioate triester. Preferably, the H-phosphonate and alcohol are protected nucleosides or oligonucleotides. Oligonucleotide H-phosphonates which can be used in the formation of phosphorothioate triesters are also provided.

Abstract: A process for the preparation of a compound of formula (1): is provided, which comprises the reaction a compound of formula (2): with a compound of formula Al(OR)3 under substantially anhydrous conditions. X, and X1 are each independently H or a protecting group, B is a base; R is an alkyl, alkoxyalkyl, alkenyl or alkynyl group, each of which may be optionally substituted, and L is a leaving group.

Abstract: A process for the synthesis of a phosphorothioate triester is provided. The process comprises the coupling of an H-phosphonate with an alcohol in the presence of a solution comprising both a coupling agent and a sulfur transfer agent. Preferably, the H-phosphorate and alcohol are protected nucleosides or oligonucleotides.

Abstract: A process for the synthesis in solution phase of a phosphorothioate triester is provided. The process comprises the solution phase coupling of an H-phosphonate with an alcohol in the presence of a coupling agent to form an H-phosphonate diester. The H-phosphonate diester is oxidised in situ with a sulfur transfer agent to produce the phosphorothioate triester. Preferably, the H-phosphonate and alcohol are protected nucleosides or oligonucleotides. Oligonucleotide H-phosphonates which can be used in the formation of phosphorothioate triesters are also provided.

Abstract: A process for the synthesis in solution phase of a phosphorothioate triester is provided. The process comprises the solution phase coupling of an H-phosphonate with an alcohol in the presence of a coupling agent to form an H-phosphonate diester. The H-phosphonate diester is oxidized in situ with a sulfur transfer agent to produce the phosphorothioate triester. Preferably, the H-phosphonate and alcohol are protected nucleosides or oligonucleotides. Oligonucleotide H-phosphonates which can be used in the formation of phosphorothioate triesters are also provided.

Abstract: Inter alia, a process for the production of a nucleoside phosphorothioate derivative corresponding to the following general formula (I): ##STR1## characterized in that it comprises reacting a salt of a nucleoside H-phosphonate corresponding to the following general formula (II): ##STR2## with a thiol transfer agent corresponding to the following general formula (III):R.sup.2 --S--X (III)in the presence of a silylating agent and a base in a suitable solvent; and working-up the reaction mixture to isolate the desired product and change the counter-cation as desired;whereinM.sup.+ represents a suitable counter-cation;R.sup.1 represents an appropriate nucleoside or nucleoside analogue;R.sup.2 represents a desired protecting group, which may ultimately be removable by cleavage of its bond to the sulfur atom; andX represents a leaving group,is disclosed.