Total synthesis of the chlorinated indigo-N-glycosides akashin A, B and C

Abstract

A total synthesis of the indigo-derived natural products akashin A-C was developed. The key step was the Nglycosylation of soluble N-benzylated-indigos with a suitably protected viosaminyl trichloroacetimidate. This donor was obtained from D-galactose. Unusual intermediates in the glycosylation reaction of N-benzylindigo (O-glycosides) were observed. The final transformations yielding akashin A required the adjustment of the

A Blueprint for Transforming Indigos to Photoresponsive Molecular Tools

“…The initially obtained product was the O ‐indigoglycoside but can undergo further rearrangement with extended reaction time to afford the desired N ‐glycoside. Pfretzschner and Unverzagt have applied this strategy to complete the total synthesis of akashins A, B, and C [64] …”