Preparation and Characterization of Rosmarinecine Derivatives
This work describes the synthesis of 8-tert-butyl-dimethylsilyloxy- (3), 2,8-bis(tert-butyldimethylsilyloxy)- (4) 2-mesyloxy-8-tert-butyldimethylsilyloxy- (5), and 2-tosyloxyros-marinecine (6) from selective protection of the different hydroxyl groups of rosmarinecine 2, which was obtained by hydrolysis of rosmarinine 1. The rosmarinine 1 naturally occuring was isolated in good yields (0.66%) from Senecio callosus. The chemoselectivity of the silylation of the hydroxyl groups at position C-2 and C-8 of 2 was controlled by the time of the reaction, which exhibited a higher reactivity for primary hydroxyl than secondary hydroxyl group, as well as the stereochemistry of the group at 1 position, which is trans and cis to the hydroxyl groups at 2 and 7 positions, respectively, where the steric efffect of hydroxyl group at 7 position is evidenced and possible effect of the solvent. The compounds were characterized by ¹H, 13C NMR, ¹H-¹H COSY, HETCOR spectra, infrared and mass spectrometry.
| Main Authors: | , |
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| Format: | Digital revista |
| Language: | English |
| Published: |
Sociedad Química de México A.C.
2006
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| Online Access: | http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1870-249X2006000400004 |
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| Summary: | This work describes the synthesis of 8-tert-butyl-dimethylsilyloxy- (3), 2,8-bis(tert-butyldimethylsilyloxy)- (4) 2-mesyloxy-8-tert-butyldimethylsilyloxy- (5), and 2-tosyloxyros-marinecine (6) from selective protection of the different hydroxyl groups of rosmarinecine 2, which was obtained by hydrolysis of rosmarinine 1. The rosmarinine 1 naturally occuring was isolated in good yields (0.66%) from Senecio callosus. The chemoselectivity of the silylation of the hydroxyl groups at position C-2 and C-8 of 2 was controlled by the time of the reaction, which exhibited a higher reactivity for primary hydroxyl than secondary hydroxyl group, as well as the stereochemistry of the group at 1 position, which is trans and cis to the hydroxyl groups at 2 and 7 positions, respectively, where the steric efffect of hydroxyl group at 7 position is evidenced and possible effect of the solvent. The compounds were characterized by ¹H, 13C NMR, ¹H-¹H COSY, HETCOR spectra, infrared and mass spectrometry. |
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