Pyridine → HCID 57956922, compound

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Reaction Steps

A solution of benzyl ester compound 10 (100 mg, 0.1968 mmol, 1.0 eq.) was dissolved in dry CH2Cl2 (10 mL) and cooled in an ice-water bath. 0.5M solution Trifluoroacetic acid (3.0 mL) was added dropwise and the resulting mixture stirred for 1 h. The mixture was allowed to warm-up to room temperature and stirred for a further 1 h. The resulting mixture was wash sequentially with 10% NaHCO3 (10 mL), H2O (10 mL), brine (10 mL) and dried the organic extract was dried over anhydrous MgSO4 and evaporation of the solvent afforded a crude. To the crude mixture was added pyridine (5.0 mL) and cooled in an ice-water bath and then benzoyl chloride (0.1 mL, 0.862 mmol) was added. The mixture was stirred for 1 h at this temperature and a further 24 h at room temperature. The yellow solution was evaporated and then purified by column chromatography on silica gel elution with 50% EtOAc-hexane afforded (5S)-5-[(N-benzoyl)amino]-4-oxo-6-phenyl-hexanoyl-L-proline benzyl ester as a pale yellow viscous oil which foams in 85% yield. 1H NMR was identical. Hydrogenolysis of this benzyl ester with 10% Pd/C (50 mg) and dry EtOAc-MeOH (3:1 ratio) (10 mL) for 48 h afforded the compound 5a in 90% yield. 1H NMR was identical as previously reported.

Provenance & Evidence