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Molecules 2009, 14(2), 598-607; doi:10.3390/molecules14020598
Communication

Stereochemistry of 16a-Hydroxyfriedelin and 3-Oxo-16-methylfriedel-16-ene Established by 2D NMR Spectroscopy

1,* , 2, 1, 1, 3 and 4
1 NEPLAM – Departamento de Química, ICEx, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Pampulha, CEP 31270-901, Belo Horizonte, Minas Gerais, Brazil 2 NEProNat - Departamento de Química – FACESA, Universidade Federal dos Vales do Jequitinhonha e Mucuri, Campus II - Rodovia MG 367 – Km 583, nº 5000, CEP 39100-000, Diamantina, Minas Gerais, Brazil 3 DEFAR, Escola de Farmácia, Universidade Federal de Ouro Preto, Rua Costa Sena, 171, CEP 35400-000, Ouro Preto, Minas Gerais, Brazil 4 Centro Tecnológico de Minas Gerais, Av. José Cândido da Silveira, 2000, CEP 31170-000, Belo Horizonte, Minas Gerais, Brazil
* Author to whom correspondence should be addressed.
Received: 20 November 2008 / Revised: 10 January 2009 / Accepted: 21 January 2009 / Published: 4 February 2009
(This article belongs to the Special Issue Triterpenes and Triterpenoids)
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Abstract

Friedelin (1), 3b-friedelinol (2), 28-hydroxyfriedelin (3), 16a-hydroxyfriedelin (4), 30-hydroxyfriedelin (5) and 16a,28-dihydroxyfriedelin (6) were isolated through fractionation of the hexane extract obtained from branches of Salacia elliptica. After a week in CDCl3 solution, 16a-hydroxyfriedelin (4) reacted turning into 3-oxo-16-methylfriedel-16-ene (7). This is the first report of a dehydration followed by a Nametkin rearrangement of a pentacyclic triterpene in CDCl3 solution occurring in the NMR tube. These seven pentacyclic triterpenes was identified through NMR spectroscopy and the stereochemistry of compound 4 and 7 was established by 2D NMR (NOESY) spectroscopy and mass spectrometry (GC-MS). It is also the first time that all the 13C-NMR and 2D NMR spectral data are reported for compounds 4 and 7.
Keywords: Salacia elliptica; Celastraceae; 16α-Hydroxyfriedelin; 3-Oxo-16-methylfriedel-16-ene Salacia elliptica; Celastraceae; 16α-Hydroxyfriedelin; 3-Oxo-16-methylfriedel-16-ene
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Duarte, L.P.; Silva de Miranda, R.R.; Rodrigues, S.B.V.R.; De Fátima Silva, G.D.; Filho, S.A.V.; Knupp, V.F. Stereochemistry of 16a-Hydroxyfriedelin and 3-Oxo-16-methylfriedel-16-ene Established by 2D NMR Spectroscopy. Molecules 2009, 14, 598-607.

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