Synthesis and Enantiodifferentiation of Isomeric 2,3,5,6,8,8a-Hexahydro-2,5,5,8a-tetramethyl-7H-1-benzopyran-7-ones (3,4-Dihydro-3-oxoedulans)
摘要:
The benzopyran derivatives 1a-d mere prepared in a biomimetic type reaction from their presumed natural precursor 3-oxo-retro-alpha-ionol, which was available from alpha-ionone by tert-butyl chromate oxidation, reduction with NaBH4, and subsequent rearrangement of the 7,8 double bond. The so-obtained geometrical isomers of 3-oxo-retro-alpha-ionol (4a/b) were separated by preparative and analytical multilayer coil countercurrent chromatography. Racemic 3-oxo-retro-alpha-ionol (4a) was esterified with (R)-(-)-2-phenylpropionic acid, and the resulting diastereomeric esters (5a/b) were isolated in pure form by preparative HPLC. Configuration at C-9 was determined by H-1 NMR spectroscopy. The isomeric ketols 6a/b obtained from esters 5a/b by enzymatic hydrolysis were subjected to thermal treatment (simultaneous distillation extraction, pH 1), yielding two pairs of diastereomeric 3,4-dihydro-3-oxoedulans (1a/b and 1c/d). The absolute configuration at C-8a was established by NOE experiments. Using on-line coupled multidimensional gas chromatography-mass spectrometry [DB-Wax/octakis(2,6-di-O-methyl-3-O-pentyl)-gamma-cyclodextrin] with selected ion monitoring mode, enantiodifferentiation of 1a-d in a number of natural sources was carried out.
Synthesis and Enantiodifferentiation of Isomeric 2,3,5,6,8,8a-Hexahydro-2,5,5,8a-tetramethyl-7H-1-benzopyran-7-ones (3,4-Dihydro-3-oxoedulans)
摘要:
The benzopyran derivatives 1a-d mere prepared in a biomimetic type reaction from their presumed natural precursor 3-oxo-retro-alpha-ionol, which was available from alpha-ionone by tert-butyl chromate oxidation, reduction with NaBH4, and subsequent rearrangement of the 7,8 double bond. The so-obtained geometrical isomers of 3-oxo-retro-alpha-ionol (4a/b) were separated by preparative and analytical multilayer coil countercurrent chromatography. Racemic 3-oxo-retro-alpha-ionol (4a) was esterified with (R)-(-)-2-phenylpropionic acid, and the resulting diastereomeric esters (5a/b) were isolated in pure form by preparative HPLC. Configuration at C-9 was determined by H-1 NMR spectroscopy. The isomeric ketols 6a/b obtained from esters 5a/b by enzymatic hydrolysis were subjected to thermal treatment (simultaneous distillation extraction, pH 1), yielding two pairs of diastereomeric 3,4-dihydro-3-oxoedulans (1a/b and 1c/d). The absolute configuration at C-8a was established by NOE experiments. Using on-line coupled multidimensional gas chromatography-mass spectrometry [DB-Wax/octakis(2,6-di-O-methyl-3-O-pentyl)-gamma-cyclodextrin] with selected ion monitoring mode, enantiodifferentiation of 1a-d in a number of natural sources was carried out.
Four new megastigmane glycosides, eucomegastigsides E1 (1), eucomegastigsides E2 (2), eucomegastigsides F1 (3), and eucomegastigsides F2 (4) were isolated from the leaves of Eucommiaulmoides Oliver. Their structures were elucidated based on extensive spectroscopic analysis and their absolute configurations were determined by comparison of experimental optical rotation (OR) to DFT calculations. In
从杜仲(Eucommia ulmoides Oliver )的叶子中分离出四个新的大麦角甙,杜仲皂苷E 1(1),杜仲皂苷E 2(2),杜仲皂苷F 1(3)和杜仲皂苷F 2(4)。根据广泛的光谱分析阐明了它们的结构,并通过比较实验旋光度(OR)与DFT计算确定了它们的绝对构型。此外,化合物1 - 4使用HPLC评估它们的ACE(血管紧张素转化酶)抑制活性。所有化合物均显示出对ACE的中等抑制作用。
Structure elucidation and phytotoxicity of C13 nor-isoprenoids from Cestrum parqui
Twelve C-13 nor-isoprenoids have been isolated from the leaves of Cestrum parqui (Solanaceae). The structure (2R,6R,9R)-2,9-dihydroxy-4-megastigmen-3-one has been assigned to the new compound. All the structures have been determined by spectroscopic means and chemical correlations. The compounds showed phytotoxic effect on the germination and growth of Lactuca sativa L. (C) 2003 Elsevier Ltd. All rights reserved.
Synthesis and Enantiodifferentiation of Isomeric 2,3,5,6,8,8a-Hexahydro-2,5,5,8a-tetramethyl-7H-1-benzopyran-7-ones (3,4-Dihydro-3-oxoedulans)
The benzopyran derivatives 1a-d mere prepared in a biomimetic type reaction from their presumed natural precursor 3-oxo-retro-alpha-ionol, which was available from alpha-ionone by tert-butyl chromate oxidation, reduction with NaBH4, and subsequent rearrangement of the 7,8 double bond. The so-obtained geometrical isomers of 3-oxo-retro-alpha-ionol (4a/b) were separated by preparative and analytical multilayer coil countercurrent chromatography. Racemic 3-oxo-retro-alpha-ionol (4a) was esterified with (R)-(-)-2-phenylpropionic acid, and the resulting diastereomeric esters (5a/b) were isolated in pure form by preparative HPLC. Configuration at C-9 was determined by H-1 NMR spectroscopy. The isomeric ketols 6a/b obtained from esters 5a/b by enzymatic hydrolysis were subjected to thermal treatment (simultaneous distillation extraction, pH 1), yielding two pairs of diastereomeric 3,4-dihydro-3-oxoedulans (1a/b and 1c/d). The absolute configuration at C-8a was established by NOE experiments. Using on-line coupled multidimensional gas chromatography-mass spectrometry [DB-Wax/octakis(2,6-di-O-methyl-3-O-pentyl)-gamma-cyclodextrin] with selected ion monitoring mode, enantiodifferentiation of 1a-d in a number of natural sources was carried out.