To a solution of PIAS-3 (115 mg, 0.

To a solution of PIAS-3 (115 mg, 0.40 mmol, 1.00 eq) inCH2Cl2 (8 mL), boron tribromide solution was added inCH,Cl2 (1.0 M, 3.6 mL, 3.6 mmol, 9.0 eq) dropwise at0 'C.After warming to room temperature over 14 h, LC-MS anal-ysisindicatedfullconversion.Sa turatedaq.NaHCO3(15 mL) was added at room temperature and the mixturewas poured on water (10 mL). After extraction of the aq.phase withEtOAc (4 x 20 mL),the combined organicphases were washed with aq ueous saturated sodium chloride(20 mL), dried and evaporated to give a black oil that waspurified by column chromatography (9 : 1 CH2Cl2 : MeOH)to give PIAS-4 as a dark-redamorphous solid(32 mg,0.13 mmol, 32%).