The standard dU nucleobase is chemically ligated with a hydrolytically impervious 5’ vinyl phosphonate (VP), an effective bioisostere of the natural 5′-monophosphate in small interfering RNAs (siRNAs). VPs are shown to enhance RNA-induced silencing complex (RISC) recognition and thus avoid the use of metabolically unstable 5’ phosphates. There is some evidence to suggest enhancement of exonuclease stability. Of particular use where a sequence is incompatible with cellular kinases and thus cannot be 5’ phosphorylated in-vitro. ⁽¹⁾

Two options are available, either OMe or POM protection. 5'-[O,O-bis(pivaloyloxymethyl)] (POM) protection allows clean and rapid one-step deprotection with addition of 3% (v/v) diethylamine to the standard aqueous ammonia deprotection solution, minimizing side reactions and impurities.

Ref:

1. Jadhav et al. ChemBioChem 2016, 17, 985 – 989.