title: Synthesis and properties of RNA analogs-oligoribonucleotide N3'-->P5' phosphoramidates.
abstract: The synthesis and characterization of RNA mimetics, uniformly modified oligoribonucleotide N3'-->P5' phosphoramidates containing all four natural bases (uracil, cytosine, adenine and guanine) as well as thymidine and 2,6-diaminopurine, are described. These RNA analogs contain N3'-->P5' phosphoramidate internucleotide linkages which replaced natural RNA O3'-->P5' phosphodiester groups. These oligonucleo-tides were constructed from novel monomeric units (2'- t -butyldimethylsilyl)-3'-(monomethoxyltrityl)-amino-nucleoside-5'- phos phoramidites, the preparation of which is also presented. Several mixed base 9-13mer oligoribonucleotide phosphoramidates were synthesized with step-wise coupling yields of 96-98%. Thermal denaturation experiments demonstrated that ribo-N3'-->P5' phosphoramidates form stable duplexes with a complementary RNA strand. Thus, the melting temperature ( T (m)) of a duplex formed by a 13mer ribo-N3'-->P5' phosphoramidate (84 degrees C) was higher than that observed for the isosequential natural RNA oligomer (64.0 degrees C), or for the 2'-deoxy-N3'-->P5' phosphoramidate counterpart (71.7 degrees C). Moreover, substitution of adenine by 2, 6-diaminopurine in an oligoribophosphoramidate pentamer resulted in a very significant increase in the duplex melting temperature ( approximately 7 degrees C per base substitution). The RNA phosphoramidates also showed similar rates of hydrolysis by both RNase A and RNase T(1)as compared to natural RNA oligomers. The data presented indicate that this class of RNA analogs may be used as structural and functional RNA mimetics.
authors.affiliation: Geron Corp., 230 Constitution Drive, Menlo Park, CA 94025, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Matray
authors.forename: S M
authors.initials: SM
authors.lastname: Gryaznov
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006358:Hot Temperature; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D018716:Molecular Mimicry; D009843:Oligoribonucleotides / Q000138:chemical synthesis*; D011489:Protein Denaturation; D006163:Ribonuclease T1 / Q000378:metabolism; D012259:Ribonuclease, Pancreatic / Q000378:metabolism
chemical_list: D009843:Oligoribonucleotides; D006163:Ribonuclease T1; D012259:Ribonuclease, Pancreatic