Ethyl chloroformate → (S)-2-(4-cyclohexyl-phenoxymethyl)-5-cyclopropyl-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-ylamine (0.5 g, 1.82 mmol), (see Example 28), in ethanol (5 mL) was added cyclopropyl-propynoic acid ethyl ester (0.377 g, 2.73 mmol) (prepared from ethynyl-cyclopropane and ethyl chloroformate in accordance with the procedures of G. Cai et al., Tetrahedron, 2006, 5697-5708). The reaction mixture was heated in a microwave oven at 170° C. for 30 min. The solvent was removed under vacuum, and the residue purified by flash column chromatography (silica gel, 2% 7N NH3 in MeOH/CH2Cl2) to afford 0.635 g of (S)-2-(4-cyclohexyl-phenoxymethyl)-5-cyclopropyl-2,3-dihydro-oxazolo[3,2-a]pyrimidin-7-one as a white solid. [α]D25 −13.40 (c 0.5, CHCl3)

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