Oligonucleotide Analogues with Integrated Bases and Backbone. Part 20

Hydrazide‐ 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 ).