-8 ir excess 1, 4-diaminobutane using the mixed-anhydride method (CICOzEt, Et3N, THF) furnished azido amide 17 (72%). However, reduction of the amide group in this substance proved troublesome and gave at best 30-35% of spermidine 8. To solve this problem, 16 was first reduced with B2H6 and then oxidized with pyridinium dichromate (PDC) to azido aldehyde 18, which smoothly condensed12 with 1, 4-diaminobutane (Pt02-H2, EtOH) to ...