Total synthesis of lycorine-type alkaloids by cyclopropyl ring-opening rearrangement

Abstract

A practical method for the synthesis of lycorine-type alkaloids with cis-B/C ring structure has been developed. Based on the reactions of aminocyclization, palladium-mediated arylation and especially cyclopropyl ring-opening rearrangement, the synthesis of anhydrocaranine, (±)-γ-lycorane and putative (±)-amarbellisine was accomplished.

Hydroamination of Dihapto‐Coordinated Benzene and Diene Complexes of Tungsten: Fundamental Studies and the Synthesis of γ‐Lycorane

“…The product was purified by flash chromatography on silica gel, eluting with AcOEt, then 1 % Et 3 N in AcOEt, yielding 27 (8 mg, 0.031, 84 % yield) as an oil. Proton NMR data match those of title compound 27 [24–37] …”

“…The first asymmetric synthesis of γ‐lycorane was reported by Mori in 1995, [23] and its structure is considered prototypical for this important class of alkaloids. In just the past five years, well over a dozen new syntheses of the lycorine family have appeared [24–37] . Of these, only one uses a benzene ring as the source of the C ring, which contains all of the stereocenters.…”

Light-induced homolysis of copper(ii)-complexes – a perspective for photocatalysis

“…26 Also in this case, the reoxidation of Cu(I) by oxygen with concurrent formation of O The group of Zhang described a synthetic procedure for the efficient regioselective chlorination of coumarins 23 (Scheme 7). 27 Again, LIH of CuCl 2 delivered chlorine radicals. Direct regioselective addition of the Cl radical to the 3-position of coumarin 23a would give rise to a stable benzylic radical 25 (path A).…”

Progress towards the Total Syntheses of Amaryllidaceae Alkaloids γ‐Lycorane

“…A practicable approach to the synthesis of (±)‐γ‐lycorane (±)‐ 6 has been accomplished by the Liu group, utilizing aminocyclization, Pd‐mediated arylation, and cyclopropyl ring‐opening rearrangement as the key steps ( Scheme 7). [33] Reductive amination of 6‐bromopiperonal 21b and primary amine 2 gave a secondary amine intermediate which was subjected to further treatment with 2 N HCl to generate the appropriate amine 3 . The amino cyclization reaction of the resulting amine 3 formed cyclopropyl ketone 33 , which was subjected to Pd‐mediated arylation followed by reduction using NaBH 4 to yield the cyclopropyl alcohol 34 in 78 % yield over two steps.…”