Uniformly modified 2'-deoxy-2'-fluoro phosphorothioate oligonucleotides as nuclease-resistant antisense compounds with high affinity and specificity for RNA targets.

"Uniformly" modified phosphodiester or phosphorothioate oligonucleotides incorporating 2'-deoxy-2'-fluoroadenosine, -guanosine, -uridine, and -cytidine, reported herein for the first time, when hybridized with RNA afforded consistent additive enhancement of duplex stability without compromising base-pair specificity. CD spectra of the 2'-deoxy-2'-fluoro-modified oligonucleotides hybridized with RNA indicated that the duplex adopts a fully A-form conformation. The 2'-deoxy-2'-fluoro-modified oligonucleotides in phosphodiester form were not resistant to nucleases; however, the modified phosphorothioate oligonucleotides were highly nuclease resistant and retained exceptional binding affinity to the RNA targets. The stabilizing effects of the 2'-deoxy-2'-fluoro modifications on RNA-DNA duplexes were shown to be superior to those of the 2'-O-methylribo substitutions. RNA hybrid duplexes with uniformly 2'-deoxy-2'-fluoro-modified oligonucleotides did not support HeLa RNase H activity; however, incorporation of the modifications into "chimeric" oligonucleotides has been shown to activate mammalian RNase H. "Uniformly" modified 2'-deoxy-2'-fluoro phosphorothioate oligonucleotides afforded antisense molecules with (1) high binding affinity and selectivity for the RNA target and (2) stability toward nucleases.

Structure-activity relationships of novel 2-substituted quinazoline antibacterial agents.

High-throughput screening of in-house compound libraries led to the discovery of a novel antibacterial agent, compound 1 (MIC: 12-25 microM against S. pyogenes). In an effort to improve the activity of this active compound, a series of 2-substituted quinazolines was synthesized and evaluated in several antibacterial assays. One such compound (22) displayed improved broad-spectrum antibacterial activity against a variety of bacterial strains. This molecule also inhibited transcription/translation of bacterial RNA, suggesting a mechanism for its antibiotic effects. Structure-activity relationship studies of 22 led to the synthesis of another 24 compounds. Although some of these molecules were found to be active in bacterial growth assays, none were as potent as 22. Compound 22 was tested for its ability to cure a systemic K. pneumonia infection in the mouse and displayed moderate effects compared with a control antibiotic, gentamycin.

Allyl group as a protecting group for internucleotide phosphate and thiophosphate linkages in oligonucleotide synthesis: facile oxidation and deprotection conditions.

[reaction: see text] The allyl group, which serves as a protecting group for an internucleotide bond for both phosphates and phosphorothioates, can be easily removed by good nucleophiles under weakly basic or neutral conditions. For a practical synthesis on solid support, camphorsulfonyloxaziridine was used as the oxidizing agent for synthesizing DNA, while the Beaucage reagent was used for preparing phosphorothioate oligomers. Both types of oligonucleotides were easily deprotected by concentrated ammonium hydroxide containing 2% mercaptoethanol.