Combining two-directional synthesis and tandem reactions: new access to 3,5-disubstituted pyrrolizidines and first total synthesis of alkaloid cis-223B

Abstract

Two new tandem reactions for the synthesis of 3,5-disubstituted pyrrolizidines and the first total synthesis of alkaloid cis-223B (in 7 steps and 43% overall yield), involving a double cross metathesis and double Michael addition as key steps, are presented.

Attempted [2]Catenane Synthesis via a Quasi[1]catenane by a Templated Backfolding Strategy

“…This synthetic detour started with a Grignard reaction of 4‐bromo‐1‐butene 11 with ethyl formate to give the symmetric secondary alcohol in quantitative yield (see Scheme ) . Subsequent oxidation with pyridinium chlorochromate (PCC) gave ketone 12 in 91 % yield over the two steps, after column chromatography …”

“…[4] Subsequent oxidation with pyridinium chlorochromate (PCC) gave ketone 12 in 91 % yield over the two steps, after column chromatography. [5] Scheme 4. Synthetic scheme of the L-(+)-tartaric acid based central core.…”

Two-directional synthesis and biological evaluation of alkaloid 5-epi-cis-275B′

“…1,6 The first and only synthesis of alkaloid cis 223B was reported by our group in 2009: the latter was obtained in 7 steps and 43% overall yield. 7 A synthesis of the trans configuration was later reported by Toyooka.…”

A two-directional approach to pyrrolizidines: total syntheses and biological evaluation of alkaloid cis-223B and (±)-xenovenine

“…1,6 The first and only synthesis of alkaloid cis 223B was reported by our group in 2009: the latter was obtained in 7 steps and 43% overall yield. 7 A synthesis of the trans configuration was later reported by Toyooka. 8 (AE)-Xenovenine was isolated in 1980 from the venom of the ant species Solenopsis xenoveneum by Jones and co-workers.…”