Unprecedented migration of [Pt(dien)]2+(dien = 1,5-diamino-3-azapentane) from sulfur to guanosine-N7 in S-guanosyl-L-homocysteine (sgh)

The species [Pt(dien)(sgh-S)]2+1 formed upon reaction of sgh with one equivalent of (PtCl(dien)Cl at 2 < pH < 6.5 is found to isomerize intramolecularly into [Pt(dien)(sgh-N7)]2+2 with Pt coordination at N7 of guanosine; upon addition of a second equivalent of [PtCL(dien)]Cl dinuclear [{Pt(dien)}2(sgh-N7,S)]4+3 is formed.