Sodium triacetoxyborohydride → ethyl (5S)-12-[(R)-[(2R,3R,4R,5S)-3,4-bis(acetyloxy)-5-(2,4-dioxo-3,4-dihydro-1(2H)-pyrimidinyl)tetrahydro-2-furanyl](hydroxy)methyl]-5-[(1S)-1-hydroxyethyl]-3,6-dioxo-1-phenyl-2-oxa-4,7,11-triazatridecan-13-oate

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Reaction Steps

A solution of [(1S,2S)-2-hydroxy-1-(3-oxo-propylcarbamoyl)-propyl]-carbamic acid benzyl ester (215 mg, 0.699 mmol, obtained from Reference Example 18) and a mixture of ethyl (2R,3R)-2-amino-3-hydroxy-3-[(2S,3R,4R,5R)-3,4-bis(acetyloxy)-5-(2,4-dioxo-3,4-dihydro-1(2H)-pyrimidinyl)tetrahydro-2-furanyl]propanoate and ethyl (2R,3R)-2-amino-3-hydroxy-3-[(2S,3R,4R,5S)-3,4-bis(acetyloxy)-5-(2,4-dioxo-3,4-dihydro-1(2H)-pyrimidinyl)tetrahydro-2-furanyl]propanoate (300 mg, 0.699 mmol) in anhydrous tetrahydrofuran (3 ml) were stirred at room temperature under a nitrogen atmosphere for 15 minutes. Acetic acid (40 μl) and sodium triacetoxyborohydride (0.296 mg, 1.4 mmole) were added and the resulting solution was stirred under nitrogen for an additional 2.5 hours. The reaction mixture was partitioned between ethyl acetate and aqueous sodium bicarbonate solution, and the aqueous layer was separated and extracted with ethyl acetate (2×75 ml). The combined extracts were washed with saturated sodium chloride solution, dried over sodium sulfate, filtered and concentrated in vacuo. The residue was chromatographed (flash column, silica gel, 5% methanol in methylene chloride) to provide ethyl (5S)-12-[(R)-[(2R,3R,4R,5S)-3,4-bis(acetyloxy)-5-(2,4-dioxo-3,4-dihydro-1(2H)-pyrimidinyl)tetrahydro-2-furanyl](hydroxy)methyl]-5-[(1S)-1-hydroxyethyl]-3,6-dioxo-1-phenyl-2-oxa-4,7,11-triazatridecan-13-oate (230 mg, 46%) as a white solid.

Provenance & Evidence