159JP84 (115 mg, 0.40 mmol) and p-toluenesulfonhydrazide (90 mg, 0.48 mmol) in absolute ethanol (1.0 mL) were refluxed overnight and the resulting white precipitate was filtered off, dried in vacuo and added to a vial containing sodium cyanoborohydride (101 mg, 1.60 mmol), N,N-dimethylformamide (2.0 mL), sulfolane (2.0 mL), p-toluenesulfonic acid (25 mg) and cyclohexane (2.0 mL). The resulting solution was heated at 110° C. for 2 days, poured into water (200 mL), extracted with ethyl acetate (2×200 mL), dried over Na2SO4, filtered, concentrated in vacuo and purified by preparative TLC (ethyl acetate/n-heptane 1:5, 5× eluted) to afford the title compound (25.3 mg, 22%) as thick oil.
