Tilak Chandra

Chemoselective Deprotection of α-Indole and Imidazole Ribonucleosides

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.

Regioselective Glycosylation: Synthesis of α-Indoline Nucleosides

Novel indoline ribonucleosides with the α-N-glycoside configuration are synthesized with very high regioselectivity in 90–96% yield, using TMS protected indolines and 2,3-O-(1-methylethylidene)-5-O-(triphenylmethyl)-α/β-d-ribofuranose. The structures of these ribonucleosides were elucidated with X-ray crystallography as well as 2D (NOESY, COSY, and HMQC) NMR spectroscopy.