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. 2010 Jan 27;51(4):609-612.
doi: 10.1016/j.tetlet.2009.11.068.

Direct organocatalytic coupling of carboxylated piperazine-2,5-diones with indoles through conjugate addition of carbon nucleophiles to indolenine intermediates

Ramin Dubey  1 , Bogdan Olenyuk
Affiliations

Direct organocatalytic coupling of carboxylated piperazine-2,5-diones with indoles through conjugate addition of carbon nucleophiles to indolenine intermediates

Ramin Dubey et al. Tetrahedron Lett. .

Abstract

The indole-diketopiperazine bridge is an important structural feature of many bispyrrolidinoindoline and epipolythiodiketopiperazine fungal metabolites. Organocatalytic conjugate addition of diketopiperazines to indoles was achieved in good to excellent yields through electrophilic indolenine intermediates generated under mild conditions. Screening of catalysts and solvents at different temperatures was performed in order to achieve high product yields.

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Figures

Figure 1
Figure 1
Natural products with cyclotryptophan motifs incorporating indole – diketopiperazine linkages
Figure 2
Figure 2
Alkylation of piperazine-2,5-dione 2a with gramine 1a
Figure 3
Figure 3
Gramine-N-oxide 1b and 1-Boc-protected gramine 1c as substrates for organocatalytic α-alkylation of diketopiperazines
Figure 4
Figure 4
Cinchona alkaloid Lewis bases used in this study
See this image and copyright information in PMC

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