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

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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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 (CC BY 3.0).

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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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