Xylose‐DNA Containing the Four Natural Bases

Oligonucleotides containing (2′‐deoxy‐β‐ D ‐xylofuranosyl)guanine have been prepared. For this purpose 2‐aminoadenosine ( 5 ) was synthesized and converted to 2′‐deoxy‐β‐ D ‐xyloguanosine ( 1 ). The related 2′‐deoxy‐β‐ D ‐xyloisoguanosine ( 3 ) and 2′‐deoxy‐β‐ D ‐xyloxanthosine ( 4 ) were also synthesized. Compound 1 was converted to the phosphonate and phosphoramidite building blocks 10 and 11 , respectively. The oligodeoxynucleotide (5′‐3′)d(xG‐xT‐xA‐xG‐xA‐xA‐xT‐xT‐xC‐xT‐xA‐xC‐T) ( 18 ) formed a duplex with the same T m as the parent (5′‐3′)‐(G‐T‐A‐G‐A‐A‐T‐T‐C‐T‐A‐C) ( 19 ), but with an inverted CD spectrum.