A Highly Efficient Synthesis of the Erythrina and B‐Homoerythrina Skeleton by an AlMe₃‐Mediated Domino Reaction

Abstract

Domino effect: The skeleton of erythrina and B‐homoerythrina alkaloids can be constructed in an efficient manner from readily available substrates (see Scheme) by a three‐step domino reaction. These natural products constitute an interesting class of compounds because of their extensive biological activity.

A Titanium(III)-Catalyzed Reductive Umpolung Reaction for the Synthesis of 1,1-Disubstituted Tetrahydroisoquinolines

“…Noteworthy families are the erythrina and spiro­benzyl­iso­quinoline alkaloids, as well as synthetic agents such as the anticonvulsants MK-801 and FR115427 (Scheme ) . The methods for the preparation of such 1,1-disubstituted frameworks showed strong limitations regarding the substrate scope and required several steps or the installation of N-protecting or N-activating groups. , To this end, we herein report a novel and unconventional approach to 1,1-difunctionalized tetra­hydroiso­quinolines in the form of a direct and broadly applicable titanium­(III)-catalyzed reductive radical acylation of 3,4-dihydroiso­quinolines. This approach closes a methodological gap in modern organic synthesis.…”

Selected Synthetic Strategies to Spirocyclics

“…Various alkaloids containing spiro linkage, such as erysodine 275, were constructed in an efficient manner by way of trimethylaluminum-mediated domino cyclization reactions (Scheme 76). 87 An efficient protocol for the construction of spirocyclic lactams starting with primary amines, cycloalkenones, and acrylic acid methyl ester in the presence of trimethylaluminum was developed. 88 Compound 278 was prepared in one step by phosphasilylation reaction from cyclopent-2-en-1-one and acrylic acid methyl ester.…”

β-Phenylethylamines and the isoquinoline alkaloids

“…133 In an alternative approach, the simple erythrinanes 212a and 212b were synthesised in a one-step process by treating homoveratrylamine and homopiperonylamine respectively with trimethylaluminium, followed by the enol acetate of the ketoester 204b, the process being represented as a domino reaction proceeding through 210 and 211. 134 Other, stepwise, routes to the erythinane skeleton have also been reported. Compound 213, claimed to be a new alkaloid, was previously isolated as comisiline, 140 and 214, also claimed as a new alkaloid, was previously isolated from from Phelline comosa.…”