Solution phase synthesis of ISIS 2922 (Vitravene) by the modified H-phosphonate approach

Abstract

The synthesis of Vitravene, a 21-mer oligonucleotide phosphorothioate (d[Gp(s)Cp(s)Gp(s)Tp(s)Tp(s)Tp(s)Gp(s)Cp(s)Tp(s)Cp(s)Tp(s)Tp(s)Cp(s)Tp(s)Tp(s)Cp(s)Tp(s)Tp(s)Gp(s)Cp(s)G]) by the modified H-phosphonate approach in solution is reported. The synthetic strategy adopted involves the use of only four different trimer building blocks. The dimer and trimer blocks are prepared by a novel four component procedure in which the coupling agent (diphenyl phosphorochloridate 5b) and the sulfur-transfer reagent (N-[(2-cyanoethylsulfanyl)succinimide] 19) are added at the same time. Yields both of the building blocks and in the block coupling reactions are very satisfactory. The fully-protected 21-mer 38 is unblocked by a five-step procedure to give Vitravene, which is isolated as its sodium salt.