Autonomously Pairing Cysteinyl-Linked Nucleotide Analogues with a Unique Architecture
摘要:
We report the efficient pairing in water of the first representative of oligonucleotide analogues in which the backbone is replaced by linking elements between the nucleobases. The architecture of the new analogue demonstrates that the structural differentiation of oligonucleotides into a contiguous backbone and nucleobases, as embodied by the natural nucleic acids and all nucleotide analogues analyzed to date, is not a prerequisite for pairing. UV and circular dichroisrn analyses of self-complementary and non-self-complementary octanucleotide analogues strongly suggest the fully reversible, sequence-specific association of our new analogues to form a left-handed double helix with an antiparallel strand orientation that is characterized by melting temperatures and free enthalpies higher than those of natural RNA and DNA of the same sequence. The linking element incorporates an L-cysteine moiety that allows a short and efficient synthesis of the monomeric building blocks and, through the choice of either L- or D-cysteine, gives access to either one of the enantiomeric oligomers and thus to left- or right-handed helices.
Abstractmagnified imageHydrazide‐ and amide‐linked oligonucleoside analogues with integrated bases and backbone were designed to allow for a rapid synthesis of long and water‐soluble oligomers. The uracil‐, cytosine‐, and adenine‐derived hydrazide building blocks 13–15 were synthesized by nucleophilic substitution with the hydrazine 23 of the halides 19, 28, and 34, derived from the alcohols 18, 27, and 33, respectively, while the uracil‐, cytosine‐, and adenine‐derived amide building blocks 45–47 were synthesized by a Curtius degradation of the carboxylic acids 51, 56, and 61. These acids were obtained by Wittig reaction of the aldehydes 49, 53, and 58. The guanine‐derived monomers 44 and 48 were synthesized by reductive cyclisation of the nitroso amides 38 and 63, respectively, resulting from acylation of the known 2,6‐diamino‐4‐(benzyloxy)‐5‐nitrosopyrimidine (37).