To a 2.0 M hexane solution of (diethylamino)dimethylaluminum (3.2 equivalents) in dry benzene (0.26 M) was cooled to −15° C., a solution of ethyl 3-(8-(2-(3-ethylureido)benzo[b]thiophene-3-carbonyl)-4-oxo-1,3,8-triazaspiro[4.5]dec-1-en-2-yl)propanoate (10 (Example 10), 12 mg, 1.0 equivalent) in THF (0.16M) was added; the mixture was heated to 80° C. for 6 hrs. The mixture was cooled in an ice bath; then a saturated aqueous Rochelle's solution was added and stirred for 1 hr, then partitioned between ethyl acetate and water and the separated organics was washed with brine and dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by preparatory LCMS to afford N,N-diethyl-3-(8-(2-(3-ethylureido)benzo[b]thiophene-3-carbonyl)-4-oxo-1,3,8-triazaspiro[4.5]dec-1-en-2-yl)propanamide (10, 20%). Two rotamers observed (ratio 1.3:1).
