Pentopyranosyl Oligonucleotide Systems. Communication No.13<FNR HREF="fnxx"></FNR> <FN ID="fnxx"> Communication No.12: [1]. The paper is also communication No.38 in the series ‘Chemistry of -Aminonitriles'. For communication No.37, see [2].</FN>

Among the members of a family of diastereoisomeric pentopyranosyl-(4'→2')-oligonucleotide systems derived from <SC>D</SC>-ribose, <SC>D</SC>-xylose, <SC>L</SC>-lyxose, and <SC>L</SC>-arabinose, the α-arabinopyranosyl system shows by far the strongest Watson&bond;Crick base pairing. The system is, in fact, one of the strongest oligonucleotide-type base-pairing systems known. It undergoes efficient cross-pairing with all the other members of the pentopyranosyl family, but not with RNA and DNA. The paper describes the synthesis and pairing of the properties of α-<SC>L</SC>-arabinopyranosyl-(4'→2')-oligonucleotides.