Borane → 2-(2-Benzyloxycarbonylamino-ethyl)-4-(tert-butyl-dimethyl-silanyloxy)-3-hydroxy-pyrrolidine-1-carboxylic acid tert-butyl ester

Participants

Reaction Conditions

Reaction Steps

A solution containing 7 (440 mg, 0.92 mmol) in anhydrous THF (15 mL) was cooled to −30° C. Borane (1M/THF, 3.68 mL) was added dropwise. After 10 min, the reaction mixture was allowed to slowly warm to 0° C. at which point TLC analysis revealed complete consumption of 7. The reaction mixture was recooled to −10° C. and 1M NaOH (2.6 mL) was added followed by the addition of 35% hydrogen peroxide (0.73 mL). The reaction mixture was then warmed to 0° C. After 1 h, the reaction mixture was quenched by the addition of saturated aqueous Na2S2O3 and the product was extracted with EtOAc. The combined organic extracts were washed successively with water and brine, dried over anhydrous Na2SO4, filtered, and concentrated. The crude product was purified by flash silica gel chromatography (4:1 hexanes/EtOAc) to afford 250 mg (55%) of 8. 1H NMR (CDCl3, 300 MHz), mixture of rotomers: δ7.25 (m, 5H), 6.07 (m, 0.6H), 5.93 (m, 0.2H), 5.67 (m, 0.2H), 5.00 (m, 2H), 4.03 (m, 1.5H), 3.84 (m, 0.75H), 3.75-3.63 (m, 1.5H), 3.54 (m, 1.25H), 3.37 (m, 0.6H), 3.26 (m, 0.4H), 3.13 (m, 1.5H), 2.95 (m, 0.75H), 1.90 (m, 1H), 1.67 (m, 1H), 1.36 (s, 9H), 0.80 (s, 9H), 0.00 (s, 6H) ppm. Mass spectrum, m/z [495.2] (M+H)+.

Provenance & Evidence