Methyl ester 11 (2.70 g, 5.33 mmol) was dissolved in THF (30 mL). Sodium hydroxide (0.853 g, 21.3 mmol) pre-dissolved in water (10 mL) was added. Methanol (15 mL) was added to obtain a homogenous solution and this was stirred at rt for 18 h before being concentrated in vacuo. The residue was partitioned between EtOAc and 1M hydrochloric acid. The aqueous phase was extracted twice more with EtOAc and the combined organic extracts were washed with brine, dried (MgSO4), filtered and concentrated in vacuo to yield a white foam, 2.50 g, 95%.
