Syntheses of 15N-enriched polyamines.

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Abstract
A total synthesis of polyamines was developed using potassium phthalimide as a sole nitrogen source. 15N-enriched phthalimide was prepared almost quantitatively from 15N-enriched ammonium sulfate by a modified method. Key compounds for the synthesis of 15N-enriched spermidine and spermine were 15N-enriched putrescine (I), N-(3-bromopropyl)phthalimide (II), N-(4-bromobutyl)phthalimide (III) and benzylamine, which were easily prepared in high yields from potassium 15N-enriched phthalimide. Spermidine was synthesized by 2 alternative methods involving an alkylation of monobenzyloxycarbonyl putrescine with II and a stepwise alkylation of benzylamine with II and III in the presence of KF-Celite. The latter method allowed the preparation of all 7 kinds of various 15N-enriched spermidines with combinations of the 3 reagents containing 15N or 14N. Spermine was similarly synthesized by alkylation of N,N''-dibenzylputrescine with II. In these methods, the alkylation using KF-Celite was extremely useful for the synthesis of spermidine and spermine. The present methods were also used to synthesize various other polyamines in high yields.