Chemoselective Deprotection of α-Indole and Imidazole Ribonucleosides

Abstract

A series of 2 ′,3 ′-isopropylidene and 5 ′-trityl-protected α-indole and α/β-benzimidazole and imidazole ribonucleosides were deprotected with different acids. Selectivity was achieved for 5 ′-versus 2 ′,3 ′- deprotection by using formic acid in the α-indole ribonucleoside series. Treatment of α-indole ribonucleosides with a mixture of formic acid and ether at room temperature afforded 2 ′,3 ′-deprotected α-ribonucleosides, whereas treatment of the α-benzimidazole ribonucleosides with the same acid afforded the 5 ′-deprotected ribonucleoside without any 2 ′, 3 ′-deprotected products. The structures of these ribonucleosides were elucidated with 2D (NOESY, COSY, and HMQC) NMR spectroscopy.

Keywords:

• Chemoselective
• coenzyme B₁₂
• biosynthesis
• glycosylation

This research was supported by the National Institute of General Medical Sciences, Grant GM 48858