A novel strategy towards the total synthesis of cyclopeptide alkaloids

Cyclic peptides I (R = benzyl, allyl; R1 = NO2, NH2, H), which contain the macrocyclic aryl ether skeleton of some naturally occurring alkaloids such as pandamine, were prepd. Key to the synthetic strategy was the cyclocondensation of the linear peptides II [NR2 = NHBOC, N(benzyl)2, N(allyl)2; R2 = SiMe2CMe3, H] to form macrocycles I. Thus, II [NR2 = N(allyl)2, R2 = H] in a DMF soln. was treated with Bu4N+F- in the presence of mol. sieves to form I (R = allyl, R1 = NO2), which was subsequently converted first to the amine I (R = allyl, R1 = NH2) and then to the target macrocycle I (R = allyl, R1 = H). [on SciFinder (R)]