[CH2:1]1[O:5][C:4]2[CH:6]=[C:7](/[CH:10]=[CH:11]/[CH:12]=[CH:13]/[C:14]([OH:16])=O)[CH:8]=[CH:9][C:3]=2[O:2]1.C(N(CC)CC)C.CS(Cl)(=O)=O.[CH2:29]([NH2:33])[CH:30]([CH3:32])[CH3:31]>ClCCl.CO>[CH3:31][CH:30]([CH2:29][NH:33][C:14](/[CH:13]=[CH:12]/[CH:11]=[CH:10]/[C:7]1[CH:8]=[CH:9][C:3]2[O:2][CH2:1][O:5][C:4]=2[CH:6]=1)=[O:16])[CH3:32]A mixture of piperinic acid (350 mg, 0.0016 mole, 1 eq) and triethylamine (0.4 ml, 0.0032 mole, 2 eq) in dichloromethane (50 ml) was stirred for 15 min at 0° C. To this mixture methanesulfonyl chloride (0.18 ml, 0.0024 mole, 1.5 eq) was added and stirred for further 30 min at 0° C. Isobutylamine (0.23 ml, 0.0024 mole, 1.5 eq) was added to the mixture and stirred for 1 h at 0° C. and 2 h at room temperature. Dichloromethane (50 ml) was added to the mixture which was then washed with 5% HCl (3×100 ml), saturated aqueous NaHCO3 (3×100 ml) and water (3×100 ml). The organic fraction was dried over anhydrous sodium sulphate, filtered and rotary evaporated to yield a yellowish solid residue. Recrystallisation from methanol yielded colourless needles of piperlonguminine (120 mg, 32% yield)2. The reaction is presumed to proceed through a mesylate ester intermediate.
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