%0 Journal Article
%T Goniomitine: An Overview on the Chemistry of This Indole Alkaloid
%A Jos¨¦ C. F. Alves
%J ISRN Organic Chemistry
%D 2013
%R 10.1155/2013/292396
%X This paper reports an overview on the chemistry of the indole alkaloid goniomitine focusing, mainly, on the methods of synthesis related to this natural product and analogs. 1. Introduction The indole alkaloids belong to the class of natural substances displaying biological activities as well as a broad structural diversity. In view of these important properties, these products are target of study in the areas of isolation, identification, and synthesis [1¨C5]. Goniomitine (1) (Figure 1) is an indole alkaloid that was isolated and identified by Randriambola et al. [6] and Hashimoto and Husson [7]. The unique structure and biological activity of goniomitine have attracted the attention of several groups. This review describes the isolation, biogenesis hypothesis, chemical transformations, and syntheses of this alkaloid and analogs. Figure 1: Natural (£¿)- and unnatural (+)-goniomitine ( 1). 2. Isolation of Goniomitine In the course of studies of the alkaloids of the genus Gonioma, Randriambola et al. [6] isolated, from the root bark of Gonioma malagasy, a crystalline compound named goniomitine with melting point of 150¡ãC (ether-methanol), £¿80¡ã (c 0.9 in CHCl3), and molecular formula C19H26N2O (HRMS, 298.2080, calculated for 298.2045). The structure of goniomitine was initially proposed as indicated in Figure 1, with 20S, 21R configuration, based on its NMR spectra. Its absolute structure was deduced through the correlation with other alkaloids from Aspidosperma found in the same plant from where goniomitine had been isolated. The relative structure of goniomitine (1) was soon after confirmed by Takano et al. [8] through the total enantioselective synthesis of the natural form of this alkaloid. It could be evidenced that the absolute structure of the compound 1 is enantiomeric to the one that had been initially proposed for 20S, 21R configuration. 3. Biogenesis of Goniomitine Randriambola et al. [6] proposed that goniomitine (1) may be derived from the Aspidosperma skeleton of vincadifformine (2) by the successive steps depicted in Scheme 1. Scheme 1: Biogenetic hypothesis of transformation of vincadifformine ( 2) into goniomitine ( 1): (a) oxidative fission of the C-5, N-4 bond; (b) decarboxylation; (c) retro-Mannich reaction; (d) nucleophilic attack of the indole nitrogen on the iminium moiety. 4. Chemical Transformations and Syntheses of Goniomitine and Analogs 4.1. Chemical Transformations of Goniomitine For the occasion of the structural determination of goniomitine (1) [6], this compound was transformed into the N-acetyl derivative 5 upon treatment
%U http://www.hindawi.com/journals/isrn.organic.chemistry/2013/292396/