The syntheses are described of polymer supports useful for the synthesis of 3'-partially protected sulfhydryl, free sulfhydryl or phosphate group containing oligonucleotides. The supports are compatible with established phosphoramidite chemistry of oligonucleotide synthesis giving rise to oligonucleotides with terminal 3'-partially protected sulfhydryl, free sulfhydryl or phosphate function during final deprotection. Crosslinking of the thiol group containing oligonucleotide to sulfhydryl group specific fluorescent probes was carried out with high selectivity, in high yields under mild conditions. 3-Aminopropylated Controlled Pore Glass (CPG) was succinylated with succinic anhydride followed by the reaction with S-(2-thio-5-nitropyridyl)-2-mercaptoethanol in the presence of dicyclohexylcarbodiimide (DCC). The resultant polymer support was reacted with 4,4'-dimethoxytrityloxyalkanthiol 5(a - c) to yield the derivatized polymer supports 5(a - c). The support 5a directly leads to oligonucleotide-3'-phosphate on deprotection with ammonical DTT at 55 degrees C while the supports 5b and 5c lead to oligonucleotide-3'-thiols or partially protected 3'-sulfhydryl group containing oligonucleotides during final deprotection.