Hydrochloric Acid → [(4R,5R)-5-(4-methylsulfonylphenyl)-2-phenyl-4,5-dihydro-1,3-oxazol-4-yl]methanol

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Reaction Steps

(2S,3R)-Ethyl-2-amino-3-[4-(methylsulfonyl)phenyl]-3-hydroxy-propanoate (Compound VIc) (10 g, 0.0348 moles) in methanol (about 100 mL) is reacted in a reaction vessel with potassium borohydride (about 2.8 g, 0.0522 moles) over about 6 hours while maintaining the temperature below about 60° C. The reaction is cooled to ambient room temperature and about 1N HCl and water (about 15 mL) are added. Thereafter, the mixture is neutralized with sodium hydroxide (about 25%) to generate (1R,2R)-2-amino-1-[4-(methylsulfonyl)phenyl]-1,3-propanediol (Compound V wherein R1 is methylsulfonyl) in situ. Next, the methanol is evaporated, followed by the addition of 1,2-dichloroethane (about 250 mL). Next, benzenecarboximidic acid ethyl ester (Compound IV wherein R2 is phenyl and R4 is ethyl) (about 7.8 g, 0.0522 moles) is added with is heated to about 85° C. for about 6 hours. The reaction is then cooled, to below about 25° C. After cooling, glycerin is added (about 50 mL). Next, the 1,2-dichloroethane is distilled by heating to about 85° C., followed by continued heating to about 105° C. to about 110° C. for about 10 hours, then followed by cooling to below about 25° C. Thereafter, water is added (about 100 mL). The resulting solids are filtered, washed with about 1 to 1 water/isopropanol, then dried to yield (4R,5R)-4,5-Dihydro-5-[4-(methylsulfonyl)phenyl]-2-phenyl-4-oxazolemethanol (Compound II wherein R1 is methylsulfonyl and R2 is phenyl).

Provenance & Evidence