New iodine derivatives of flavonol and isoflavone.
The reaction of the flavonol 3,7,3', 4'-tetra-O-methylquercetin (1) and of the isoflavone 7,4'-di-O-methylgenistein (2) with alkaline iodine in methanol afforded four new iodine derivatives: 8-iodo-5-hydroxy-3,7,3', 4'-tetramethoxy- flavone (1a) and 6-iodo-5-hydroxy-3,7,3', 4'-tetramethoxyflavone (1b) from 1; 2 afforded a mixture of two compounds, identified as a racemic mixture of (+/-)-trans-5-hydroxy-2,3,7,4'-tetramethoxy-8-iodo-isoflavanone (2a) and (+/-)-trans-5-hydroxy-2,3,7,4'-tetramethoxy-6,8-diiodo-isoflavanone (2b). The formation of these different products reveals a significant difference involving the chemical interaction between the reactive site of alpha, beta-unsaturated ketones of flavonol and isoflavone under the tested reaction conditions (using I2/KOH/MeOH). Furthermore, the trans stereo selectivity is noteworthy in the nucleophylic addition of methanol at the isoflavone alpha, beta-unsaturated system. The structures were identified on the basis of spectral data, mainly 1D and 2D NMR and mass spectra.
Carvalho
Mário G de
MG
Departamento de Química, ICE, Universidade Federal Rural do Rio de Janeiro, Seropédica, RJ, Brasil, 23890-000.
Silva
Virginia C da
VC
Silva
Tânia M S da
TM
Camara
Celso A
CA
Braz-Filho
Raimundo
R
D005419:Flavonoids / Q000737:chemistry*; D007455:Iodine / Q000737:chemistry*; D007529:Isoflavones / Q000737:chemistry; D013057:Spectrum Analysis
D005419:Flavonoids; D007529:Isoflavones; D007455:Iodine