A Facile Synthesis of α-N-Ribosyl-Asparagine and α-N-Ribosyl-Glutamine Building Blocks

Adenosine diphosphate ribosylation (ADP-ribosylation) is a widely occurring post-translational modification of proteins at nucleophilic side chain of amino acid residues. Elucidation of ADP-ribosylation events would benefit greatly from the availability of well-defined ADP-ribosylated peptides and analogues thereof. In this paper we present a novel approach to the chemical synthesis of ribosylated amino acid building blocks using traceless Staudinger ligation. We describe an efficient and stereoselective synthesis of alpha-N-ribosyl-asparagine (alpha-N-ribosyl-Asn) and alpha-N-ribosyl-glutamine (alpha-N-ribosyl-Gln) building blocks starting from 5-tert-butyldiphenylsilyl-beta-D-ribofuranosyl azide. The N-glycosyl aminoacids are produced in good yields as pure alpha-anomers, suitably protected for peptide synthesis.