摘要:
A series of analogues and homologues of spermine were synthesized, and their impact on MK-801 binding to the N-methyl-D-aspartate (NMDA) receptor was evaluated. These tetraamines encompass both linear and cyclic compounds. The linear molecules include norspermine, N-1,N-11-diethylnorspermine, N-1,N-13-bis(2,2,2-trifluoroethyl)spermine, homospermine, and N-1,N-14-diethylhomospermine. The cyclic tetraamines consist of the piperidine analogues N-1-N-3-bis(4-piperidinyl)-1,3-diaminopropane, N-1,N-4-bis(4-piperidinyl)-1,4-diaminobutane, N-1,N-4-bis(4-piperidinylmethyl)-1,4-diaminobutane, and N-1,N-4-bis[2-(4-piperidinyl)ethyl]-1,4-diaminobutane and the pyridine analogues N-1-N-3-bis(4-pyridyl)-1,3-diaminopropane, N-1,N-4-bis(4-pyridyl)-1,4-diaminobutane, N-1,N-4-bis(4-pyridylmethyl)-1,4-diaminobutane, and N-1,N-4-bis[2-(4-pyridyl)-ethyl]-1,4-diaminobutane. This structure-activity set makes it possible to establish the importance of charge, intercharge distance, and terminal nitrogen substitution on polyamine-regulated MK-801 binding in the NMDA channel. Four families of tetraamines are included in this set: norspermines, spermines, homospermines, and tetraazaoctadecanes. Calculations employing a SYBYL modeling program revealed that the distance between terminal nitrogens ranges between 12.62 and 19.61 Angstrom. The tetraamines are constructed such that within families cyclics and acyclics have similar lengths but different nitrogen pK(a)'s and thus different protonation, or charge, states at physiological pH. The pK(a) values-for all nitrogens of each molecule and its protonation state at physiological pH are described. The modifications at the' terminal nitrogens include introduction of ethyl and beta,beta,beta-trifluoroethyl groups and incorporation into piperidinyl or pyridyl systems. The studies clearly indicate that polyamine length, charge, and terminal nitrogen substitution have a significant effect on how the tetraamine regulates MK-801 binding to the NMDA receptor. Thus a structure-activity basis set on which future design of MK-801 agonists and antagonists can be based is now available.