Branched-chain and unsaturated 1,7-diaminoheptane derivatives as deoxyhypusine synthase inhibitors

Deoxyhypusine synthase catalyzes the first step in the posttranslational biosynthesis of the unusual amino acid hypusine [N epsilon-(4-amino-2-hydroxybutyl)lysine] in eukaryotic translation initiation factor 5A (eIF-5A). eIF-5A and its single hypusine residue are essential for cell proliferation. Two series of 1,7-diaminoheptane derivatives were prepared and tested as inhibitors of human deoxyhypusine synthase. These include branched-chain saturated derivatives and both branched- and straight-chain unsaturated derivatives providing size and positional variation in branching and different torsional constraints. Of the branched-chain compounds, 7-amino-1-guanidinooctane (39) proved to be the most potent inhibitor in vitro (IC50, 34 nM), while 1,7-diamino-trans-hept-3-ene (20a) displayed the greatest inhibition (IC50, 0.7 microM) among the unsaturated compounds. Compound 39 also provided effective inhibition of hypusine production in Chinese hamster ovary cells in culture. Considerations of the in vitro inhibition data reported here, along with earlier findings, allowed some speculation concerning the conformation of the substrate spermidine during its productive interaction at the active site of deoxyhypusine synthase.