from the group consisting of morpholine, N,N-diisopropylamine and --OCH2 CH2 CN, and X is an oxygen atom, a sulfur atom or a pair of electrons; wherein R1 and R2 are stable to conditions of polynucleotide synthesis, wherein said first polynucleotide is attached to said liking agent via R3 moiety, and wherein said first polynucleotide and said linking agent together form an adapter molecule; (b) l