Borane → 8-(4-Hydroxymethyl-bicyclo[2.2.2]oct-1-yl)-1,3-dipropyl-3,7-dihydro-purine-2,6-dione

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Reaction Steps

4-(2,6-Dioxo-1,3-dipropyl-2,3,6,7-tetrahydro-1H-purin-8-yl)-bicyclo[2.2.2]octane-1-carboxylic acid (IX, Example 85a, 1 wt) and tetrahydrofuran (11 vol) are mixed under nitrogen. Borane.tetrahydrofuran complex (1 M) in THF (5.1 vol) is added at such a rate as to maintain the internal temperature between 10 to 20°. The mixture is stirred at 10 to 20° for 17 to 20 hours until all of the acid (X) is consumed (TLC; dichloromethane/methanol, 9/1, visualization UV then potassium permanganate). Methanol (4.2 vol) is added to the reaction, prior to heating at reflux for 45 to 75 min. The reaction is cooled to between 15 and 40° and the solvent removed by reduced pressure at 40 to 45°. The residue is partitioned between ethyl acetate (16.6 vol) and hydrochloric acid (1 M, 2.5 vol) and the aqueous layer is removed with any undissolved solid material. This mixture is clarified and the residual organic phase from the filtration of the aqueous layer/solid mixture is combined with the bulk organic phase. Saturated sodium hydrogen carbonate (2.5 vol) is added and the layers separated, retaining any solids with the aqueous phase. This aqueous phase/solid mixture is filtered and the residual organic phase from these mother liquors is combined with the bulk organic phase. The combined organic phases are washed with saline (2.5 vol), the layers are separated and any residual solid is retained with the aqueous phase. The aqueous phase/solid mixture is filtered and any organic in the mother liquors from the filtration is combined with the bulk organic phase, dried with magnesium sulphate (0.5 wt) for 5 to 15 mins, filtered, washed with ethyl acetate (1 vol) and the solvent removed under reduced pressure at 40 to 45° to give the title compound.

Provenance & Evidence