The substituted 5, 10-methylenetetrahydrofolate model (3a) derived from addition of the dianion of dimethyl 2-methoxycarbonylglutarate to 1, 5, 5-trimethyl-3-tosyl-1-imidazolidinium iodide (1) transfers a 7-carbon functionalized fragment to tryptamine to yield precursors of deethylepieburnamonine and deethyleburnamonine.