Abstract: Oligonucleotides that are capable of passive diffusion across cell membranes are disclosed. These oligonucleotides contain at least two nucleotide residues and show a log distribution coefficient in octanol:water of about 0.0-2.5 and a solubility in water of at least 0.001 .mu.g/mL. In preferred embodiments, either at least 80% of the internucleotide linkages are non-ionic, or at least 80% of the bases contain lipophilic hydrocarbyl substitutions, or a combination of these sums to 80%. These oligonucleotides may be conjugated to label and used to visualize cells.

Abstract: The internally cyclized congeners of hydroxy-substituted nucleotide analogues have been found to exhibit substantially lower toxicity in vivo than their uncyclized analogues, while retaining essentially the same antiviral activity. This was unexpected because the prior art suggested that the cyclic analogues offered no significant advantages in respect to toxicity. This finding permits the administration of much greater doses of the cyclic congeners than otherwise would have been possible and allows the clinician to omit toxicity ameliorating interventions. Novel compounds are provided for use in the method of this invention. Novel methods for the preparation of these compounds also are provided.

Abstract: Nucleotide analogs characterized by the presence of an amidate linked amino acid or an ester linked group which is bonded to the phosphorus atom of phosphonate nucleotide analogs are disclosed. The analogs comprise a phosphoamidate or ester bond that is hydrolyzed in vivo to yield a corresponding phosphonate nucleotide analog. Methods and intermediates for their synthesis and use are described.

Abstract: Oligonucleotides that are capable of passive diffusion across cell membranes are disclosed. These oligonucleotides contain at least two nucleotide residues and show a log distribution coefficient in octanol:water of about 0.0-2.5 and a solubility in water of at least 0.001 .mu.g/mL. In preferred embodiments, either at least 80% of the internucleotide linkages are non-ionic, or at least 80% of the bases contain lipophilic hydrocarbyl substitutions, or a combination of these sums to 80%. These oligonucleotides may be conjugated to label and used to visualize cells.