2,3,-Diphenyl-3-hydroxypropionic acid

A mixture of 8.5 g. a,a-diphenyl- -hydroxypropionic acid hydrazide, LiAlH4, and ethylmorpholine heated 4 hrs. at 100° 5.1 g. y-amino-/ ,j5-diphenylpro-... 

Benzaldehyde dimethylacetal (200 pi, 1.33 mmol) and a catalytic amount of p-toluenesulfonic acid (37 mg) are added to methyl (2R,3S)-3-(4-nitrobenzenesulfonamido)-3-phenyl-2-hydroxypropionate (315 mg, 0.83 mmol) in toluene 5 ml. The mixture is heated at 100°C under reduced pressure (15 mm mercury) with no condenser. After 1 h the crude reaction mixture is diluted with ethyl acetate and washed with water (2 times). After drying the organic layer over magnesium sulfate the crude material is purified by column chormatography (silica gel eluting with ethyl acetate/cyclohexane, 35/65) to give the (2S,4S,5R)-2,4-diphenyl-3-(4-nitrobenzenesulfonamido)-5-methoxycarbonyl-l,3-oxazolidine, melting point 118°-120°C. 

THF (13.5 ml) and DMF (1.5 ml) are cooled to -35°C and degased by alternating reduced pressure and nitrogen three times. Thiophenol (0.22 ml, 2.14 mmol) is added followed by potassium butoxide/THF (1.978 M, 0.7 ml, 1.38 mmol). After 5 min, 7-SDMS baccatin III 13-(2R,4S,5R)- and (2S,4S,5R)-2,4-diphenyl-3-(4-nitrobenzenesulfonamido)-l,3-oxazolidine-5-carboxylic acid ester (877 mg, 0.762 mmol) is added. After the solids are added, the reaction mixture is slowly warmed to -10°C. The mixture is stirred at -10°C until the red color fades to yellow. After 3 h the bath is dropped allowing the mixture to warm to 20-25°C. At 20°-25°C the reaction is stirred for 1 h before assaying by TLC and HPLC. Sodium bisulfite (241 mg, 2.31 mmol) is added in water (5 ml). The mixture is stirred at 20°-25°C and after approximately 115 h the reaction is complete (by TLC) giving the free amine 7-SDMS baccatin III 13-(2R,3S)-3-amino-3-phenyl-2-hydroxypropionate. 

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