Process for preparing dithiophosphate oligonucleotide analogs via nucleoside thiophosphoramidite intermediates

• US 5,218,088 A
• Filed: 11/02/1989
• Issued: 06/08/1993
• Est. Priority Date: 11/02/1989
• Status: Expired due to Term

• Current Assignee: Purdue Research Foundation (Purdue University)
• Original Assignee: Purdue Research Foundation (Purdue University)
• Inventors: Gorenstein, David, Farschtschi, Nassar
• Primary Examiner(s): Brown, Johnnie R.
• Assistant Examiner(s): Kunz, Gary L.
• Application Number:
  US07/430,733
• Time in Patent Office: 1,314 Days
• Field of Search: 536/27, 536/28, 536/29, 558/95
• US Class Current: 536/25.34
• CPC Class Codes: C07H 19/10 with the saccharide radical esterified by phosphoric or polyphosphoric acids
• CPC Class Codes: C07H 19/20 with the saccharide radical esterified by phosphoric or polyphosphoric acids
• CPC Class Codes: C07H 21/00 Compounds containing two or more mononucleotide units having separate phosphate or polyphosphate groups linked by saccharide radicals of nucleoside groups, e.g. nucleic acids

Abstract

A method for synthesis of oligonucleotide analogs having dithiophosphate internucleosidic linkages is described. Monohalohydrocarbylthiophosphoramidites are utilized to prepare nucleoside thiophosphoramidite intermediates which are activated for nucleoside coupling with tetrazole catalysts. Sulfur oxidation and dehydrocarbylation of the coupled thiophosphite intermediates provide oligonucleotide analogs having achiral dithiophosphate internucleosidic linkages.

Claims

1. In a method for coupling a first nucleoside or first oligonucleoside having a 5'"'"'-hydroxyl and 3'"'"'-protected hydroxyl group with a second nucleoside or oligonucleoside having 3'"'"'-hydroxyl and a 5'"'"'-protected hydroxyl group to form an oligonucleoside coupled through a thiophosphite linkage by reacting said second nucleoside or oligonucleoside with a compound of the formula ##STR1## wherein X is chloro, bromo, or a secondary amino group, R₁ is a hydrocarbyl radical containing up to 10 carbon atoms, and A is a secondary amino group, to form thiophosphoramidite of the formula ##STR2## wherein G is selected from the group consisting of a hydroxyl protecting group, a solid support, a nucleoside, a nucleotide and nucleotide analogs;

R₂ is hydrogen or protected hydroxyl group;

B is an amino-protected base; and

A and R₁ are as defined above;

the improvement which comprises

reacting said thiophosphoramidite with the first nucleoside or oligonucleoside in the presence of a nitrogen acid having a pKa equivalent to or greater than that of tetrazole.

2. The method of claim 1 wherein the A is a group of the formula -NR₃ R₄ wherein R₃ and R₄, taken separately, each represents alkyl, aralkyl, cycloalkyl and cycloalkylalkyl containing up to 10 carbon atoms or R₃ and R₄, when taken together with the nitrogen atom to which they are attached, form a 5- or 6-membered ring.

3. The method of claim 1 wherein A is diisopropylamino.

4. The method of claim 1 wherein the nitrogenous acid is tetrazole.