Total Syntheses of Rhodiolosides A and D and of Sachalinols A–C

Abstract

The glucosylated monoterpenoids (–)‐rhodioloside A and (–)‐rhodioloside D from the roseroot (Rhodiola rosea) have been synthesized for the first time. Glucosylation with tetrapivaloylglucosyl bromide proved superior to the use of tetraacetylglucosyl bromide or glucosyl iodides. Acid‐catalyzed cyclization of a homoglycidol‐type geraniol derivative afforded the monoterpenoid tetrahydrofuran (+)‐sachalinol C from Rhodiola sachalinensis. The absolute configuration of (+)‐sachalinol C requires revision. (–)‐Sachalinol A and (–)‐sachalinol B were also obtained.

Trio Catalysis Merging Enamine, Brønsted Acid, and Metal Lewis Acid Catalysis: Asymmetric Three‐Component Aza‐Diels–Alder Reaction of Substituted Cinnamaldehydes, Cyclic Ketones, and Arylamines

“…As expected, these reactions did not give any product, confirming once again that aliphatic amines (hard bases) are not compatible with hard metal Lewis acids and strong Brønsted acids. Based on these data and the results in previous work involving binarya cid catalysis [4b-i] and BINOL-derived phosphoric acid, [8] we proposed ap ossible transition state for this transformation (Figure 2). In this model, Y III coordinates to one of the oxygen atoms of phosphoric acid;t he nitrogen atom of (E)-1-azadiene binds to Y III and thus is activated;t he hydrogen of the enamine intermediate forms ah ydro-Scheme2.ADA reactionso fb -substituted enal 1h.…”