Backbone modified oligonucleotide analogues

An oligonucleotide analogue in which at least one of the subunits of the analogue have the structure:

• ##STR9## wherein B.sub.x is a variable base;
• Q is O;
• X is C.sub.1 to C.sub.10 lower alkyl, substituted lower alkyl, alkaryl or aralkyl;
• F;
• Cl;
• Br;
• CN;
• CF.sub.3 ;
• OCF.sub.3 ;
• OCN;
• O--, S--, or N-alkyl;
• O--, S--, or N-alkenyl;
• SOCH.sub.3 ;
• SO.sub.2 CH.sub.3 ;
• ONO.sub.2 ;
• NO.sub.2 ;
• N.sub.3 ;
• NH.sub.2 ;
• heterocycloalkyl;
• heterocycloalkaryl;
• aminoalkylamino;
• polyalkylamino;
• or substituted silyl;
• L.sub.1 is CH.sub.2 ;
• L.sub.2 is P(O)R.sub.4 ;
• L.sub.3 is O;
• L.sub.4 is CH.sub.2 ;
• R.sub.4 is OH, SH, NH.sub.2, O-alkyl, S-alkyl, NH-alkyl, O-alkylheterocyclo, S-alkylheterocyclo, N-alkylheterocyclo or a nitrogen-containing heterocycle.