200392-49-0Relevant academic research and scientific papers
Synthesis and conformational analysis of hexahydroisoquino[3,2-b][3]benzazepines (iso-B-homoberbines)
Zlotos, Darius Paul,Meise, Werner
, p. 2137 - 2157 (2007/10/03)
A new simple synthetic approach to the hexahydroisoquino[3,2-b][3]-benzazepines has been developed. 3-Benzyl-2-tetralones (3a-c) were prepared in two different ways from 2-tetralone and 6-methoxy-2-tetralone. Regioselective methoxycarbonylation with dimethyl carbonate or with magnesium methyl carbonate gave the known ss-keto esters (1) or (1′), respectively, which could be alkylated to benzyl derivatives (2) and (2′), respectively. Demethoxycarbonylation using lithium iodide afforded the desired 3-benzyl-2-tetralones (3a-c), which furnished the lactams (4a-c) by submitting to the Schmidt reaction. Reduction using borane and a final Pictet-Spengler cyclization gave the title compounds (6a-c). NMR measurements indicated that iso-B-homoberbines exist as equilibrium mixture of the cis and trans conformers in CDCl3 solution at room temperature, whereas the hydrochloride salt of 6b adopts a cis B-fused conformation.
