Triethylamine → tert-butyl 3-({(3R,4S)-3-acetamido-3-(tert-butylcarbamoyl)-4-[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)propyl]pyrrolidin-1-yl}methyl)-7-chloro-3,4-dihydroisoquinoline-2(1H)-carboxylate

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Reaction Steps

A stirred mixture of (3R,4S)-3-acetamido-N-tert-butyl-4-[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)propyl]pyrrolidine-3-carboxamide hydrochloride (226 mg, 0.524 mmol) and Et3N (0.110 mL, 0.786 mmol) in methylene chloride (2.5 mL) was treated with a solution of tert-butyl 7-chloro-3-formyl-3,4-dihydroisoquinoline-2(1 H)-carboxylate (155 mg, 0.524 mmol) in methylene chloride (2.5 mL). After stirring for 20 min, sodium triacetoxyborohydride (233 mg, 1.10 mmol) was added and stirring was continued for 1 h. The resulting mixture was carefully quenched with saturated aqueous NaHCO3 (5 mL), diluted with saturated aqueous sodium chloride (15 mL) and extracted with methylene chloride (4×15 mL). The combined organic phase was dried over Na2SO4 and concentrated. Purification by silica gel chromatography (40 g column, 2-4% MeOH in ethyl acetate) gave tert-butyl 3-({(3R,4S)-3-acetamido-3-(tert-butylcarbamoyl)-4-[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)propyl]pyrrolidin-1-yl}methyl)-7-chloro-3,4-dihydroisoquinoline-2(1 H)-carboxylate (296 mg, 84%, mixture of diastereomers) as a clear gum. LC-MS gives ESI+ MS found for C35H56BClN4O6 m/z 675.4 (M+H).

Provenance & Evidence