Hexamethyldisilazane → 9-[(1RS,4SR)-4-hydroxy-cyclopent-2-en-1-yl]guanine

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Reaction Steps

105.8 g (0.7 mol) of guanine are reacted in 600 ml of dry xylene with 500 ml of hexamethyldisilazane and 4 g of ammonium sulfate for 2 days to give the pertrimethylsilyl compound. The oily silylguanine compound is dissolved in 400 ml of dry tetrahydrofuran and the solution is added dropwise to a solution of the palladium(0) catalyst (5 mol %) prepared in situ as described above in 450 ml of tetrahydrofuran at 0° C. A solution of the equivalent amount of epoxycyclopentene in 200 ml of tetrahydrofuran is then added dropwise over a period of 2-3 hours. The resulting solution is stirred at room temperature for 3 days. 400 ml of methanol are added and the mixture is heated under reflux for 1 hour. During this operation, a very voluminous precipitate is formed, and can be converted into a homogeneous suspension after further stirring. The suspension thus obtained is filtered. 4.7 g of a mixture of the compounds 1.12.1. and 1.12.2. crystallize out of the filtrate. The residue on the filter is stirred with 1.2 l of water and filtered off with suction again. This residue on the filter is washed with ethanol and then boiled up in several portions with 1 l of ethanol. On cooling, this ethanolic solution gives 4.75 g of 9-[(1RS,4SR)-4-hydroxy-cyclopent-2-en-1-yl]guanine as beige crystals of melting point 265°-273° C. (decomposition) (compound of Example 1.12.1.). 1H NMR (270 MHz, de-DMSO), δ[ppm]: 10.56 (s, 1H), 7.60 (s, 1H), 6.42 (s, 2H), 6.15 (m, 1H), 5.95 (m, 1H), 5.24 (d, 1H), 5.20 (m, 1H), 4.70 (m, 1H), 2.82 (m, 1H), 1.60 (m, 1H). If the residue on the filter is boiled up again with 1.5 l of water, 5.0 g of 7-[(1RS,4SR)-4-hydroxy-cyclopent-2-en-1-yl]guanine of melting point >310° C. crystallize out of the aqueous filtrate (compound of Example 1.12.2.). 1H NMR (270 MHz, d6 -DMSO), δ[ppm]: 10.80 (s, 1H), 7.84 (s, 1H), 6.15 (m, 1H), 6.13 (s, 2H), 6.01 (m, 1H), 5.61 (m, 1H), 5.18 (d, 1H), 4.68 (m, 1H), 2.88 (m, 1H), 1.60 (m, 1H). The residue which remains on the filter of 82.7 g consists of a mixture of the compounds of Example 1.12.1. and 1.12.2.

Provenance & Evidence