jm049303k_si_001.pdf (157.91 kB)
Inhibition of Nucleoside Transport Proteins by C8-Alkylamine-Substituted Purines
journal contribution
posted on 2005-01-13, 00:00 authored by Reynier A. Tromp, Ronald F. Spanjersberg, Jacobien K. von Frijtag Drabbe Künzel, Adriaan P. IJzerman4-Nitrobenzylthioinosine (NBTI, 1) is a well-known inhibitor for the nucleoside transport protein
ENT1. Here we report on the synthesis and the biological evaluation of compounds that are
less polar than NBTI. Compound screening in our laboratory indicated that introduction of an
alkylamine substituent at the C8-position of N6-cyclopentyladenosine (CPA, 2) led to an
increment in affinity for the transport protein. It was investigated whether this would also
apply for NBTI derivatives. Two series of C8-alkylamine-substituted compounds were prepared,
one in which the nitro group was absent (46−58) and another in which the ribose moiety was
replaced by a benzyl group (72−75). Comparison of the biological data of these compounds
with 6-benzylthioinosine (4, Ki = 53 nM) and 9-benzyl-6-(4-nitrobenzylsulfanyl)purine (59, Ki
= 135 nM) confirmed the hypothesis. The Ki values improved upon elongation of the alkylamine
chain from methylamine to n-hexylamine with an optimum for n-pentylamine (50, Ki = 2.3
nM). Substitution with 2-methylbutylamine (52), cyclopropylamine (53), cyclopentylamine (54,
72), and cyclohexylamine (55, 73) revealed that the presence of a bulky group enhanced the
affinity. The presence of tertiary amines obtained by substitution with pyrrolidine, piperidine,
and morpholine gave only poor results. For both series substitution with cyclopentylamine
was most effective. Compound 54 (LUF5942) proved the most active, showing a comparable
affinity (Ki = 0.64 nM) to NBTI but a significantly lower polar surface area.