Synthesis and Properties of 2′‐Deoxy‐1′,2′‐seco‐D‐ribosyl (5′ → 3′)oligonucleotides (= 1′,2′‐seco‐DNA) containing adenine and thymine

Some 2′‐deoxy‐1′,2′‐seco‐D‐ribosyl (5′→3′)oligonucleotides (= 1′,2′‐seco‐DNA), differing from natural DNA only by a bond scission between the centers C(1′) and C(2′), were synthesized and studied in order to compare their structure properties and pairing behavior with those of corresponding natural DNA and homo‐DNA oligonucleotides (2′,3′‐dideoxy‐β‐D‐glucopyranosyl oligonucleotides). Starting from (−)‐D‐tartaric acid, 2′‐deoxy‐1′,2′‐secoadenosine derivative 9a and 1′,2′‐secothymidine ( 9b ) were obtained in pure crystalline form. Using the phosphoramidite variant of the phosphite‐triester method, a dinucleotide monophosphate 1′,2′‐seco‐d(T 2 ) was synthesized in solution, while oligonucleotides 1′,2′‐seco‐d[(AT) 6 ], 1′,2′‐seco‐d(A 10 ) and 1′,2′‐seco‐d(T 10 ) were prepared on solid phase with either automated or manual techniques. Results of UV‐ and CD‐spectroscopic as well as gel‐electrophoretic studies indicated that neither adenine‐thymine base pairing (as observed in natural DNA and homo‐DNA), nor the adenine‐adenine base pairing (as observed in homo‐DNA) was effective in 1′,2′‐seco‐DNA, Furthermore, hybrid pairing was observed neither between 1′.2′‐seco‐DNA and natural DNA nor between 1′,2′‐seco‐DNA and homo‐DNA.