Abstract: The invention relates to a process for the preparation of oligonucleotides by the following steps: reaction of a nucleoside with a phosphine derivative, reaction of the nucleotide derivative thus obtained with a nucleoside bonded to a polymeric carrier, oxidation of the carrier-bound nucleoside-nucleotide thus obtained with formation of phosphotriester groups, blocking of free primary 5'-OH groups, elimination of a protective group from the terminal 5'-OH group, where appropriate single or multiple repetition of the abovementioned steps to introduce further nucleoside phosphate or oligonucleoside phosphate units, and cleavage of the nucleoside-carrier bond and, where appropriate, elimination of all protective groups present in the oligonucleoside phosphates. The phosphine derivative used is a compound of the general formula III ##STR1## in which X and L can react with OH groups of the sugar units in the oligonucleotides, and R.sup.3 is a protective group which can be liberated by .beta.-elimination.

Abstract: The invention relates to a process for the preparation of oligonucleotides by the following steps: reaction of a nucleoside with a phosphine derivative, reaction of the nucleotide derivative thus obtained with a nucleoside bonded to a polymeric carrier, oxidation of the carrier-bound nucleoside-nucleotide thus obtained with formation of phosphotriester groups, blocking of free primary 5'--OH groups, elimination of a protective group from the terminal 5'--OH group, where appropriate single or multiple repetition of the abovementioned steps to introduce further nucleoside phosphate or oligonucleoside phosphate units, and cleavage of the nucleoside-carrier bond and, where appropriate, elimination of all protective groups present in the oligonucleoside phosphates. The phosphine derivative used is a compound of the general formula III ##STR1## in which X and L can react with OH groups of the sugar units in the oligonucleotides, and R.sup.3 is a protective group which can be liberated by .beta.-elimination.