Triisopropyl borate → (6-(2-((tert-Butoxycarbonyl)amino)ethyl)-1,3-dimethyl-2,4-dioxo-2,3,4,6-tetrahydro-1H-pyrrolo[3,4-d]pyrimidin-5-yl)boronic acid

Participants

Reaction Conditions

Reaction Steps

2-(1,3-Dimethyl-2,4-dioxo-1,2,3,4-tetrahydro-pyrrolo[3,4-d]pyrimidin-6-yl)-ethyl]-carbamic acid tert-butyl ester (step 3) (1.8 g, 5.58 mmol) was dissolved in anhydrous THF (49 ml) at room temperature. The flask was then evacuated and backfilled with nitrogen (×3) and cooled to −78° C. (external). After 10 mins, LDA (0.731 M, 22.92 ml, 16.75 mmol in THF, freshly prepared by standard procedure from BuLi and diisopropylamine) was charged over 3 mins. After 15 mins at −78° C., triisopropyl borate (3.87 ml, 16.75 mmol) was charged drop wise over 2 mins and the reaction held for 2 hr at −78° C. The reaction was then quenched with saturated NH4Cl solution (10 mL) via syringe under nitrogen and diluted with water (60 mL) and EtOAc (40 mL). The layers were separated and the aqueous extracted with EtOAc (4×50 mL). The combined organics were washed with brine (20 mL), dried (Na2SO4) and filtered under reduced pressure to afford a pale yellow solution. The solvent volume reduced by half under reduced pressure to afford a suspension of a white solid. The solid was recovered by reduced pressure filtration and dried in air, followed by heating to 50° C. under vacuum for 3 h. This afforded the title compound as a white crystalline solid.

Provenance & Evidence