Synthesis of locked nucleic acid derivatives
The invention relates to a novel strategy for the synthesis of Locked Nucleic Acid derivatives, such as α- L -oxy-LNA, amino-LNA, α- L -amino-LNA, thio-LNA, α- L -thio-LNA, seleno-LNA and methylene LNA, which provides scalable high yielding reactions utilising intermediates that also can produce other LNA analogues such as oxy-LNA. Also, the compounds of the formula X are important intermediates that may be reacted with varieties of nucleophiles leading to a wide variety of LNA analogues.
1. A method for the synthesis of a compound of the general formula IV
wherein
X is —O—
Z is —CH 2
B is a nucleobase;
R 3 is selected from —R H , —N 3 , —NR H R H* , —NR H C(O)R H*, —C(O)NR H R H*, —OR H , —OC(O)R H , —C(O)OR H , —SR H , —SC(O)R H , and tri(C 1-6 -alkyl/aryl)silyloxy;
each R H and R H* independently being selected from hydrogen, optionally substituted C 1-6 -alkyl, optionally substituted aryl, and optionally substituted aryl-C i-6 -alkyl;
A 4 and A 5 independently are selected from C 1-6 -alkylene; and
R 5 is selected from iodo, bromo, chloro, C 1-6 -alkylsulfonyloxy optionally substituted with one or more substituents selected from halogen and phenyl optionally substituted with one or more substituents selected from nitro, halogen and C 1-6 -alkyl, and arylsulfonyloxy optionally substituted with one or more substituents selected from nitro, halogen, C 1-6 -alkyl, and C 1-6 -alkyl substituted with one or more halogen;
said method comprising the following steps:
treating an intermediate of the general formula I:
wherein
X, B, R 3 , A 4 , and A 5 are as defined above;
R 2 is selected from iodo, C 1-6 -alkylsulfonyloxy optionally substituted with one or more substituents selected from halogen and phenyl optionally substituted with one or more substituents selected from nitro, halogen and C 1-6 -alkyl, and arylsulfonyloxy optionally substituted with one or more substituents selected from nitro, halogen, C 1-6 -alkyl, and C 1-6 -alkyl substituted with one or more halogen; R 3 and R 2 may together form an epoxide and
R 4 and R 5 independently are as defined for R 5 above, or R 4 and R 5 together constitutes a tetra(C 1-6 -alkyl)disiloxanylidene group;
with a nucleophile selected from organometallic hydrocarbyl radicals, so as to substitute R 2 , and
effecting ring-closure between the C2′ and C4′ positions so as to yield the LNA analogue of the formula IV.
2. The method according to claim 1 , wherein
R 2 is selected from C 1-6 -alkylsulfonyloxy optionally substituted with one ore more halogen, and arylsulfonyloxy optionally substituted with one or more substituents selected from nitro, halogen, C 1-6 -alkyl, and C 1-6 -alkyl substituted with one or more halogen;
R 3 is optionally substituted aryl(C 1-6 -alkyl)oxy; and
R 4 and R 5 are independently selected from C 1-6 -alkylsulfonyloxy optionally substituted with one or more halogen an arylsulfonyloxy optionally substituted with one or more substituents selected from nitro, halogen, C 1-6 -alkyl, and C 1-6 -alkyl substituted with one or more halogen.
3. The method according to claim 1 , wherein A 4 and A 5 are methylene.
4. The method according to claim 1 , wherein R 4 and R 5 are identical.
5. The method according to claim 1 , wherein B is selected from adenine, guanine, 2,6-diaminopurine, thymine, 2-thiothymine, cytosine, methyl cytosine, uracil, 5-fluorocytosine, xanthine, 6-aminopurine, 2-aminopurine, 6-chloro 2-amino-purine, and 6-choropurine, R 2 is selected from C 1-6 -alkylsulfonyloxy substituted with one or more halogen, R 3 is benzyl, and R 4 and R 5 are independently selected from C 1-6 -alkylsulfonyloxy optionally substituted with one or more substituents selected from halogen and C 1-6 -alkyl substituted with one or more halogen.
6. The method according to claim 1 , wherein R 4 and R 5 are independently selected from methanesulfonyloxy, trifluoromethanesulfonyloxy, ethanesulfonyloxy, 2,2,2,-trifluoroethanesulfonyloxy, propanesulfonyloxy, iso-propanesulfonyloxy, butanesulfonyloxy, nonafluorobutanesesulfonyloxy, pentanesulfonyloxy, cyclopentanesulfonyloxy, hexanesulfonyloxy, cyclohexanesulfonyloxy, 2-chloro-α-toluenesulfonyloxy, ortho-toluensulfonyloxy, meta-toluenesulfonyloxy, para-toluenesulfonyloxy, benzenesulfonyloxy, ortho-bromobenzenesulfonyloxy, meta-bromobenzenesulfonyloxy, para-bromobenzenesulfonyloxy, ortho-nitrobenzenesulfonyloxy, meta-nitrobenzenesulfonyloxy, and para-nitro-benzenesulfonyloxy.
7. The method according to claim 1 , wherein the intermediate has the formula III
wherein B, R 4 and R 5 are as defined in claim 1 , and wherein R 3 is —OR H or —OC(O)R H , where R H is as defined in claim 1 .
8. The method according to claim 1 , wherein B is selected from adenine, guanine, 2,6-diaminopurine, thymine, 2-thiothymine, cytosine, methyl cytosine, uracil, 5-fluorocytosine, xanthine, 6-aminopurine, 2-aminopurine, 6-chloro-2-amino-purine, and 6-chloropurine, R 3 is benzyl, and R 4 and R 5 are both methylsulfonyloxy.