Patent Advancement and Expertise
based upon phosphorothioate work by chemistry scientist
Dr. Wolfgang K.-D. BRILL
In 2008 a patent was published citing the groundbreaking disclosure of work made by Dr. Wolfgang K-D Brill relating to phosphorothioate synthesis. This is derived from a paper entitled ‘Thioalkylation of nucleoside-Hphosphonates and its application to solid phase synthesis of oligonucleotides’. As mentioned in ‘Tetrahedron Letters’, (1995) 36, 703-706.
Dr. Brill’s outstanding work in disclosing a process in which an Hphosphonate Diester is reacted with a silylating agent in order to form a silyl phosphite was a pivotal aspect in assisting the advancement of the patent.
Dr. Brill’s inventive steps and expertise is acknowledged as thus:
The present invention relates to a supported Hphosphonate diester subjected to sulfur transfer with a sulfur agent to form a phosphorothioate ester. The prior art documents D1: BRILL W. KD: discloses a process in which an Hphosphonate diester is reacted with a silylating agent in order to form a silyl phosphite. This silyl phosphite is then subjected to sulfur transfer with a sulfur transfer agent. BRILL W. KD does not disclose a process in which an H phosphonate diester is subjected to sulfur transfer with a sulfur transfer agent. Accordingly, BRILL W. KD does not destroy the novelty of the present claims.
Regarding the inventive step, the process of the present invention disclosed that a supported Hphosphonate diester is subjected to sulphur transfer with a sulphur transfer agent to form a phosphorothioate trimester. BRILL W. K.D discloses the solid phase preparation of a phosphorothioate trimester by a process comprising the formation of a solid supported Hphosphonate diester, silylation to form a silylphosphite, and reaction with a source of a thioalkly group to form the phosphorothioate triester. WO 99 09041 A discloses a solution phase process the preparation of a phosphorothiate triesterby a process comprising the formation of an Hphosphonate diester and reaction with a sulphur transfer reagent to form the phosphorothioate triester. EPA0 739 899 discloses that certain solid supports can be employed in the synthesis of oligonucleotides. The claims of the present invention involve an inventive step over the teaching of BRILL W. KD, either alone, or in combination with either or both of WO 99 09041 A and EPA0 739 899. A skilled person consulting BRILL W. KD would perceive that the core teaching of BRILL W. KD is the thioaklylation of Hphosphonates via a silylphosphite intermediate. Thus, the very last change a skilled person would be motivated to make to the process of BRILL W. KD would be to omit the silylation step. Indeed, it would be perverse of the skilled person to omit the core step of the teaching of BRILL W. KD. The skilled person reading BRILL W. KD without benefit of the knowledge of the present invention would not ignore the benefits taught by BRILL W. KD for the silylation step (page 703 2nd paragraph, last 3 lines). Accordingly, the process of claim 1 would not be obvious to the skilled person in view of BRILL W. KD. Further, the present invention would not be obvious to one of the ordinary skill in the art in view of the combination of BRILL W. KD and WO 99 09041 A without the benefit of knowledge of the present invention. The clear teaching of BRILL W. KD is that the syntheses of phosphorothioate trimesters by the Hphosphonate route on a solid phase requires the intermediate silylation step in order to yield the desired product. It is submitted that it would be extremely perverse of the skilled person to choose to omit such a key teaching from the process of BRILL W. KD. While, WO 99 09041 A discloses a process in which an Hphosphonate diester is reacted directly with a sulfur transfer agent, the process disclosed is a solution phase process and hence does not anticipate the claimed invention. The skilled person; would recognize that the conducting of reactions on solid supports places markedly different constraints on the process chemistry, especially in terms of reaction kinetics, resulting from the lower freedom of movement of molecules attached to, a solid support, and also from surfaces effects caused by the presence of the solid support. Accordingly, the skilled person would not expect simply to substitute the process chemistry of WO 99 G9041 A for the process of BRILL W. KD. In fact, the skilled person aware of the teaching of BRILL W. KD would, conclude that it was precisely the difficulties associated with conducting reactions on a solid support which resulted in the teaching of BRILL W. KD concerning the importance of the silylation state. Additionally, EPA0 739 899 does not provide a teaching that would motivate the skilled person to ignore the clear teaching of BRILL W. KD. Therefore, the skilled person, based on a fair teaching of BRILL W. KD and WO 99 09041 A, and without the benefit of knowledge of the present invention, would simply not consider replacing the chemistry of BRILL W. KD with the chemistry of WO 99 09041 A. Accordingly, the claims of the present application would not be obvious over BRILL W. KD, WO 99 09041 A and EPA0 739 899, and accordingly involve an inventive step. 'The Hphosphonate employed in the process of the present invention is ofterran Hphosphonate monoester, and advantageously a protected nucleoside or oligonucleotide. Hphosphonate, preferably comprising a 5' or a/3' Hphosphonate function, particularly preferably a 3' Hphosphonate function. Preferred nucleosides are 2'. " deoxyribonucleosides and ribonucleosides; preferred oligonucleotides are oligodeoxyribonudeotides and oligoribonucleotides. 2'deoxyribonucleosides and oligodeoxyribonucleotides may comprise 2'CalkyI and 2'Calkenyl substituents.
When the Hphosphonate building block is a protected deoxyribonudeosrde, ribonucleoside, oligodeoxyribonucleotide or oligoribonucleotide derivative comprising a 3' Hphosphonate function, the 5' hydroxy function is advantageously protected by a suitable protecting group. Examples of such suitable protecting groups include acid labile protecting groups, particularly trityl and substituted trityl groups such as dimethoxytrityl and '.9phenylxanthen9yl groups; and base label protecting groups such as FMOC. Further protecting groups that may be employed include silyl ether groups.
The above mentioned patent is with reference to the following:
Title of Invention: Process for the preparation of Phosphorothioate Triesters and Oligonucleotides
Abstract: A process for the synthesis of a phosphorothioate triester comprising the reaction, in the presence of a coupling agent, of an Hphosphonate with a substrate comprising a free hydroxy group and bonded to a solid support, thereby forming a supported Hphosphonate diester, and subjecting the Hphosphonate diester to sulphur transfer with a sulphur transfer agent thereby forming a phosphorothioate triester.
PCT International Classification Number: C07H 1/00
PCT International Application Number: PCT/GB00/03912
PCT International Filing date: 2000-10-12
Inventors: Mark Edward DOUGLAS, James EN MELLOR, John David MOODY, Kevin Gerard SCOTT
Click on the link to see a video of Dr. Wolfgang K.-D. Brill discussing Oligonucleotide Phosphorodithioates: Discover Future Drugs + MORE...
Specialist in organic chemistry, combinatorial chemistry, oligonucleotide chemistry, QMA and GMP.
