Total Synthesis of the Slime Mold Alkaloids Arcyroxocin A and B

Abstract

The synthesis of the slime mold pigments arcyroxocin A and B is described. The key step in the synthesis is the oxidative ring closure of an N-protected 3-(4-hydroxyindol-3-yl)-4-indol-3-ylmaleimide with DDQ/PPTS, which affords exclusively the desired arcyroxocin derivative. Attempts to obtain the arcyroxocin system from a 3-(4-hydroxyindolyl)-4-(2-oxoindolinyl)maleimide precursor were less successful and led to oxidative formation of a spiroindoline compound.

Key words

alkaloids from myxomycetes - oxidative cyclization - oxocin ring formation - arcyroxocins

References

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1

Responsible for X-ray crystal structure determinations.

10

The exchange of EtMgCl for LiHMDS did not improve the yield (compare, however, ref. 9a).

18

Crystallographic data for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publications no. CCDC 267603 (9a), CCDC 783129 (9b), and CCDC 228174 (20). Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1 EZ, UK [fax: [phone] or e-mail: [e-mail]].