An efficient synthesis of the ribozyme–folate conjugate

γ-Cysteamine modified folic acid was synthesized by reductive alkylation of N2-iBu-6-formylpterin with suitably protected cysteaminyl-l-glutamyl-p-aminobenzoic acid, followed by deprotection. Following activation with 2,2′-dipyridyl disulfide, this synthon was conjugated to the 5′-end of 5′-thiol modified ribozyme to afford target ribozyme–folate conjugate in a good yield.