New Synthesis of the Alkaloid Polonicumtoxin C

Two new short syntheses of the alkaloid polonicumtoxin C (3) are presented. In the first pathway, polonicumtoxin C was obtained in two steps by alkylation of 6-methyl-2,3,4,5-tetrahydropyridine with E-4-bromo-3-methyl-1-(tetrahydro-2-pyranyloxy)-2-butene 7 and subsequent deprotection of the THP group. In the second pathway, the cyclic ketimine was constructed via a short sequence of reactions involving (a) sequential alkylation of the N-(isopropylidene)isopropylamine with N,N-disilylprotected ω-bromopropylamine and E-4-bromo-3-methyl-1-(tetrahydro-2-pyranyloxy)-2-butene 7, (b) transimination and deprotection, the latter two reactions occurring in one step.