Synthesis of oligo-2′-O-methylribonucleotides containing α-amino acid residues in 2′-position

Abstract

Oligo 2´ O methylribonucleotides containing residues of phenylalanine, histidine, and lysine amides were synthesized with the use of new phosphoramidites of 2´ aminoacid deriva tives of uridine.Derivatives of oligonucleotides are widely used in mo lecular biology and medicine due to their unique ability to bind to complementary sequences of DNA and RNA, which can result in a selective suppression of expression of certain genes. At present, an intensive research work is being carried out aimed at the design of effective thera peutic preparations based on nucleic acids. 2, 3 Elaboration of methods for the synthesis of artificial ribonucleases is one of trends in chemistry of nucleic acids. 4,5 A cell or viral RNA may serve as the potential targets, which determines the topicality of this task in the first place. Very often, in the design of artificial ribo nucleases it is preferable to combine, in one molecule, an oligonucleotide complementary to the given region of RNA and a substance that catalyzes hydrolysis of certain phosphodiester bonds of the ribonucleic acid after forma tion of a two stranded complex (duplex). For example, attempts were undertaken at constructing artificial ribo nucleases based on oligonucleotides containing imidazole and primary aliphatic amine residues. 5, 6 It was shown earlier that in the presence of basic amino acids and short peptides containing polyamine residues a remarkable increase in the rate of cleavage of the RNA target takes place upon its treatment with ribozymes un der deficiency in magnesium ions. 7 In this connection, it can be supposed that oligonucleotides bearing basic amino acid residues can also possess ribonuclease activity. Thus, the development of efficient methods for the synthesis of amino acid derivatives of oligonucleotides is quite justi fied. The heterocyclic bases in the catalytic sites of ribozymes are often involved into various non covalent interactions essential for maintaining their structure and catalytic activity; the ribose residue, in particular its 2´ position, seems to be the most preferable for the modi fication. In the present work, a promising method of 2´ functionalization was used, which is based on the for mation of a carbamate bond between primary or second ary alcohol and primary aliphatic amine upon treatment with N,N´ carbonyldiimidazole 8 or N,N´ disuccinimidyl carbonate (DSC). 9 It was noted 8,9 that oligonucleotide derivatives containing N substituted carbamate bonds with involvment of the 2´ hydroxy group of uridine form duplexes with complementary DNA or RNA; these du plexes have low thermal stability. At the same time, it is known that many 2´ О alkyl derivatives of oligoribo nucleotides form particularly stable duplexes with comple mentary RNAs. 10 For example, it was shown 11 that analo gous 2´ derivatives do not decrease stability of the com plex of modified oligonucleotide with complementary RNA. In order to avoid the negative effect of the modifi cation on the hybridization properties of oligonucleotides, we have developed an ...