Ethyl chloroformate → (S)-2-(4-Cyclohexyl-phenoxymethyl)-5-ethoxy-2,3-dihydro-oxazolo[3,2-a]pyrimidin-7-one

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To a solution of (S)-5-(4-cyclohexyl-phenoxymethyl)-4,5-dihydro-oxazol-2-yl-amine (0.98 g, 3.58 mmol) (prepared in accordance with the procedures described in Steps 1 and 2 of Example 1 starting from R-epichlorohydrin and 4-cyclohexylphenol) in 50 ml of ethanol was added freshly prepared 3-ethoxy-propynoic acid ethyl ester (0.65 g, 4.58 mmol), prepared from 6 ml of 50% ethoxyacetylene and 3.3 ml of ethyl chloroformate (Synthesis, 1989, 123-4). The mixture was stirred for 15 min at room temperature after which it was stirred at 60-65 degrees C. for 6h. The reaction mixture was concentrated to a yellow solid, dissolved in dichloromethane and flash chromatographed on silica gel eluting with dichloromethane/ammonia/methanol to provide 0.544 g of the title compound as a white solid. [α]D25 −1.00 (c 0.5, CHCl3).

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