Bicyclo[2.2.1]heptane-1-methanesulfonic acid, 7,7-dimethyl-2-oxo-, (1S)- → ((3aR,4R,6R,6aS)-6-(6-chloro-9H-purin-9-yl)-2-ethoxytetrahydro-3aH-cyclopenta[d][1,3]dioxol-4-yl)methanol

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Reaction Steps

The above crude (1R,2S,3R,5R)-3-((5-amino-6-chloropyrimidin-4-yl)amino)-5-(hydroxymethyl)cyclopentane-1,2-diol was treated with ethyl orthoformate (120 mL, 720 mmol) and 10-camphorsulfonic acid (8.11 g, 34.9 mmol). The heterogeneous brown mixture was stirred vigorously to afford a nearly homogeneous brown solution after 10 min. At 5 h, LC MS indicated the desired product as the major product and the reaction was quenched with saturated aqueous NaHCO3 (120 mL). The mixture was diluted with water (75 mL), extracted with CH2Cl2 (3×200 mL), and the combined organics were dried (Na2SO4) and concentrated in vacuo to afford the crude title compound as a dark brown liquid, which was carried on without further manipulation: MS (ESI+) for C14H17ClN4O4 m/z 341.0 (M+H)+.

Provenance & Evidence