7- SDMS Baccatin III

Then the (2S,4S,5R)-2,4-diphenyl-3-(4-nitrobenzenesulfonamido)-5-carboxy-1,3-oxazolidine react with the 7-SDMS Baccatin III, that is 7-(3-methylbut-2-yl)dimethylsilyl baccatin III (Baccatin III 7,ll-methano-lH-cyclodeca(3,4) benz(l,2-b)oxet-5-one,6,12b-bis(acetyloxy)-12(benzoyloxy)-l,2a,3,4,4a,6, 9,10,ll,12,12a,12b-dodecahydro-4,9,ll-trihydroxy-4a,8,13,13-tetramethyl-, (2aR,4S,4aS,6R,9S,llS,12S,12aR,12bS), isolated from Taxus baccata). 

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. 

Sodium bicarbonate (485 mg, 5.77 mmol) and water (10 ml) are added to 7-SDMS baccatin III 13-(2R,3S)-3-amino-3-phenyl-2-hydroxypropionate. The mixture is cooled to 0°C and then benzoyl chloride (150 ml, 1.3 mmol) is added. After 1 hr the reaction is complete and the reaction mixture is diluted... 

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