Abstract: A process for the purification of an oligonucleotide synthon is provided. The process comprises subjecting an organic solution comprising an oligonucleotide synthon and lower molecular weight impurities to nanofiltration whereby the ratio of an oligonucleotide synthon to lower molecular weight impurities in the solution is increased after the nanofiltration. Preferably, the oligonucleotide synthon is a nucleoside phosphoramidite or nucleoside H-phosphonate. The nanofiltration membrane is preferably a polyimide membrane having a molecular weight cut off of 400.

Abstract: A method for the analysis of oligonucleotides is provided. The method comprises: desalting a mixture of oligonucleotides under conditions such that there is substantially no separation of the mixture of oligonucleotides, and/or by on-line desalting, introducing the desalted mixture of oligonucleotides into a mass spectrometer; and quantifying one or more oligonucleotides comprised in the mixture by mass spectrometry.

Abstract: A process for the synthesis of an oligonucleotide is provided in which an oligonucleotide is assembled on a swellable solid support using the phosphoramidite approach in the presence of an activator, wherein the activator is not tetrazole or a substituted tetrazole. Preferred activators are pyridinium, imidazolinium and benzimidazolinium salts; benzotriazole and derivatives thereof; and saccharin or a saccharin derivative. Preferred swellable solid supports comprise functionalised polystyrene, partially hydrolysed polyvinylacetate or poly(acrylamide).

Abstract: A process for the preparation of an oligonucleotide is provided. The process comprises the assembly of an oligonucleotide attached to a solid support, wherein the solid support is prepared by a process comprising polymerisation of a monomer which comprises a protected hydroxypolyC2-4 alkyleneoxy chain attached to a polymerisable unit wherein the protected hydroxypolyC2-4 alkyleneoxy chain contains from 2 to 10 C2-4 alkyleneoxy groups and wherein the hydroxypolyC2-4 alkyleneoxy chain is protected with an acid-labile protecting group, preferably an optionally substituted trityl group.

Abstract: Oligonucleotide comprising at least one internucleotide phosphorus atom protected with a group of formula —XaSiR3R4R5 provided. Xa represent 0 or S, and R3, R4 and R5 each independently are optionally substituted hydrocarbyl groups, selected such that that total number of carbon atoms in R3 plus R4 plus R5 is 4 or more. Process for the preparation of these oligonucleotides, intermediate compounds useful therein, and process for the preparation of the intermediate compounds are also provided.

Abstract: A process for the synthesis of an oligonucleotide is provided in which an oligonucleotide is assembled on a swellable solid support using the phosphoramidite approach in the presence of an activator, wherein the activator is not tetrazole or a substituted tetrazole. Preferred activators are pyridinium, imidazolinium and benzimidazolinium salts; benzotriazole and derivatives thereof; and saccharin or a saccharin derivative. Preferred swellable solid supports comprise functionalised polystyrene, partially hydrolysed polyvinylacetate or poly(acrylamide).

Abstract: A process for the purification of an oligonucleotide synthon is provided. The process comprises subjecting an organic solution comprising an oligonucleotide synthon and lower molecular weight impurities to nanofiltration whereby the ratio of an oligonucleotide synthon to lower molecular weight impurities in the solution is increased after the nanofiltration. Preferably, the oligonucleotide synthon is a nucleoside phosphoramidite or nucleoside H-phosphonate. The nanofiltration membrane is preferably a polyimide membrane having a molecular weight cut off of 400.

Abstract: A process for the preparation of an oligonucleotide is provided. The process comprises the assembly of an oligonucleotide attached to a solid support, wherein the solid support is prepared by a process comprising polymerisation of a monomer which comprises a protected hydroxypolyC2-4 alkyleneoxy chain attached to a polymerisable unit wherein the protected hydroxypolyC2-4 alkyleneoxy chain contains from 2 to 10 C2-4 alkyleneoxy groups and wherein the hydroxypolyC2-4 alkyleneoxy chain is protected with an acid-labile protecting group, preferably an optionally substituted trityl group.