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The structure and the biological significance of naturally occurring and synthetic polyamine analogues and conjugates are presented and the available methodologies for their synthesis are described. These methodologies involve either the selective functionalization of the amino functions, using suitable protecting groups or acylating agents, or fragment synthesis protocols. The latter employ suitable amino components and simple reactions, like Michael addition to α,β‐unsaturated nitriles, alkylation of amines and sulfonamides, reductive alkylation and acylation followed by reduction of the thus‐obtained amides, as key‐reactions, or azides as key‐intermediates, for the assembly of the polyamine skeleton. Syntheses performed in solution as well as in the solid phase are discussed.

In a cell-free system derived from Escherichia coli,various analogues of spermine were used to study their effect on the binding of AcPhe-tRNA to poly (U)-programmed ribosomes and on the puromycin reaction carried out at 6 mM Mg 2ϩ (Ac, acetyl). In the absence of factors washable from ribosomes (FWR fraction), mono-acylated or di-acylated analogues of spermine stimulate the binding of AcPhe-tRNA to a lesser degree than spermine, in the order: N 1 -acetylspermine Ͼ N 1 ,N 12 -diacetylspermine Х N 1 ,N 12 -dipivaloylspermine. Also, the above analogues do not show any sparing effect on Mg 2ϩ requirements for AcPhe-tRNA binding to ribosomes, in contrast to spermine. The presence of FWR fraction during the binding or acetylation of the secondary amines of spermine moderates or abolishes the stimulatory effect.In addition, all analogues tested enhance the stability of the ternary complex AcPhe-tRNA-poly(U)-ribosome and the extent of AcPhe-puromycin synthesis, particularly in the absence of the FWR fraction. At the kinetic phase of AcPhe-puromycin synthesis, the analogues display both stimulatory and inhibitory effects, depending on the absence (partial noncompetitive inhibition) or the presence of the FWR fraction (nonessential activation in concert with partial noncompetitive inhibition). Detailed kinetic analysis shows that the analogues tested can mimic the behaviour of spermine, however, the potency to affect the peptidyltransferase activity depends on their degree of acylation, acyl-substituent size, charge distribution and on their chain flexibility.Keywords : acylated polyamine; protein synthesis; puromycin reaction; peptidyltransferase.Polyamines are organic polycations that are protonated at physiological pH and can potentially interact with a variety of cellular macromolecules including nucleic acids and proteins [1]. Substantial evidence exists suggesting a significant role of polyamines in regulating the translation process at several levels [1]. Due to its four positive charges, spermine is the most effective of the naturally occurring polyamines both in regulating the ribosomal functions and in decreasing the Mg 2ϩ requirements for protein synthesis. Tabor and Tabor [2] have reported that endogenous spermine does not exist in Escherichia coli. However, small amounts of spermine, about two orders of magnitude lower than those of spermidine, can be detected in E. coli by more sensitive methods [3]. Extensive biochemical studies have focused on the mechanism of spermine biological action in prokaryotic-cell-free systems, since this polyamine consists the parent compound of a large number of synthetic polyamine analogues with antiparasitic and antitumor activity [4Ϫ6].Evidently, spermine markedly stimulates the activity of several in vitro protein-synthesizing systems characterized by low Mg 2ϩ concentrations near those observed in vivo [7Ϫ10]. In a recent report [11], we have demonstrated that, at 6 mM Mg 2ϩ spermine exhibits a concentration-dependent allosteric biphasic

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