Synthesis of Pentacyclic Core Structure ofAspidospermaAlkaloids by Sequential Ring Construction via Oxidative Phenolic Coupling

Construction of Hydroindole Skeleton by Photocatalytic Oxidative Dearomatization and Cyclization Sequence, and a Concise Synthesis of Melodamide A and (±)-Toussaintine C

“…Since dimethyl acetal 21 was obtained, we attempted the aza-Michael addition under acidic conditions without using MeOH. Odagi and Nagasawa reported the aza-Michael addition by using HCl/1,4-dioxane in CH 2 Cl 2 . We followed their reported procedure to obtain hydroindole 11a in 91% yield without racemization (entry 7).…”

“…Odagi and Nagasawa reported the aza-Michael addition by using HCl/1,4-dioxane in CH 2 Cl 2 . 15 We followed their reported procedure to obtain hydroindole 11a in 91% yield without racemization (entry 7). From these results, it can be concluded that in the aza-Michael addition reaction of tyrosine derivatives where racemization is a concern, HCl is preferred, whereas in the aza-Michael addition reaction of tyramine derivatives where racemization is not a concern, the use of Triton B is desirable because of slightly higher yield compared with entries 4 and 7.…”